
MOON CALCULATOR  
Version 6.0  

Program & documentation by Dr. Monzur Ahmed
49 Kempson Avenue, Birmingham, B72 1HE, U.K.

Email:     monzur@bigfoot.com	
           monz@starlight.demon.co.uk
	     
Homepages: http://www.starlight.demon.co.uk/mooncalc
           http://www.ummah.org.uk/ildl/mooncalc.html

Released:  10th October 2001

----------------------------------------------------------------------------


"The sun must not catch up the moon, nor does the night outstrip the 
day. Each one is travelling in an orbit with its own motion"
(Al Qur'an 36:40)
	
"the sun and the moon (are subjected) to calculations"
(Al Qur'an 55:5)




----------------------------------------------------------------------------
CONTENTS
----------------------------------------------------------------------------

0. COPYRIGHT

1. INTRODUCTION

2. GETTING STARTED

	2.1 Minimum system requirements

	2.2 Files included

	2.3 Making Backups

	2.4 Running MOON CALCULATOR on a floppy drive system

	2.5 Installing and running MOON CALCULATOR on a hard drive system


3. USING THE PROGRAM

	3.1 Option 1. Summary tables of Moon Data
	    3.1.1 Screen 1 of 4
	    3.1.2 Screen 2 of 4
	    3.1.3 Screen 3 of 4
          3.1.4 Screen 4 of 4		
	    3.1.5 Earliest new moon sighting for a given location
 
	3.2 Option 2. Moon position on Starchart (Dec vs RA)

	3.3 Option 3. Simulation of Local Sky  (Alt vs Azi)

	3.4 Option 4. Close-up of Moon

	3.5 Option 5. First Crescent Sighting (Global Scan)
	    3.5.1 Moon sighting criteria used in program
	
	3.6 Option 6. Hijri Calendar Tabulation
          3.6.1 Local Calendar
          3.6.2 Trizonal Calendar (text mode)
          3.6.3 Trizonal Calendar (map mode)

	3.7 Option 7. Libration Graph

	3.8 Option 8. Eclipses

	3.9 Option 9. Add/ Delete/ Change/ View Atlas Data
          3.9.1. Add data
	    3.9.2. Delete data
	    3.9.3. Change data
	    3.9.4. View data

	3.10 Option 10. Change Options
          3.10.1 Default City
	    3.10.2 Mode of time entry
	    3.10.3 Start and End of Summer Time/Daylight Saving Time
	    3.10.4 Monitor Type
	    3.10.5 Map Type
	    3.10.6 Visibility Criterion
	    3.10.7 Interval between longitudes
	    3.10.8 Interval between latitudes
	    3.10.9 Lower limit of latitude
	    3.10.10 Upper limit of latitude
	    3.10.11 Topocentric or Geocentric
	    3.10.12 Correction for refraction	
	    3.10.13 Apparent or Geometric sunset
	    3.10.14 Atmospheric temperature
	    3.10.15 Atmospheric pressure	


4. FUTURE DEVELOPMENTS

5. ACKNOWLEDGEMENTS

6. DISCLAIMER

7. GLOSSARY

8. ABBREVIATIONS USED

9. GENERAL MOON INFORMATION

10. FREQUENTLY ASKED QUESTIONS

11. CONCLUSION

12. SELECTED REFERENCES



-------------------------------------------------------------------------------
0. COPYRIGHT
-------------------------------------------------------------------------------

Moon Calculator (MoonCalc), associated data files and this document are
copyright (c) by Dr. Monzur Ahmed 1993-2001. All rights reserved.

Data/graphics/maps produced by MoonCalc may be used if accompanied by the 
following acknowledgement:

"data/graphics/map* from MoonCalc 6.0 by Dr. Monzur Ahmed."

(*as appropriate)

Data produced by MoonCalc must not be used for commercial purposes.

If MoonCalc data are used on a Web page, a link may be made to one or both of the 
MoonCalc homepages:

http://www.starlight.demon.co.uk/mooncalc
http://www.ummah.org.uk/ildl/mooncalc.html

MoonCalc may be copied and distributed freely as long as all files are copied 
and no charge is made (other than a nominal charge for media). The program must 
be distributed as its ORIGINAL and UNMODIFIED zip file (moonc60.zip). 

No alterations should be made to the program, documentation or data files apart 
from the atlas database, TOWNS.DAT.

Although MoonCalc may be distributed freely, it is not 'Public Domain' nor is it 
'Freeware'. All rights remain with the author, Dr. Monzur Ahmed.


-------------------------------------------------------------------------------
1. INTRODUCTION
-------------------------------------------------------------------------------

MoonCalc provides information relating to the position, age, phase, orientation, 
appearance and visibility of the moon for any given date, time and location on 
earth. It also provides the Julian Day Number, Magnetic Declination, time and 
direction of moonrise and moonset, interval between sunset and moonset, interval 
between sunrise and moonrise, date/time of astronomical new moon (conjunction), 
full moon, apogee and perigee and predicts the likelihood of visualising the 
young moon from a particular location. Data pertaining to solar and lunar 
eclipses in any year are also shown. MoonCalc provides Hijri calendar data 
including location dependent Hijri date conversion using predicted crescent 
visibility. Automatic local and regional (tri-zonal) Hijri calendar tabulation
is possible.

The program can scan the globe at the start of any lunar month to find the 
location, date/time and circumstances of earliest crescent sighting using a variety 
of ancient and modern moon sighting criteria. The program is able to draw world 
maps (flat and spherical projections) showing areas of the globe where the young 
moon is likely to be seen. 

Graphical displays showing the position of the moon on a star chart and the 
position of the moon in a simulated local sky (horizon view or traditional 
circular sky-chart view) can be produced and printed out. A close-up of the near 
side of the moon (showing orientation of the moon's limbs and position of the 
lunar craters), correct for a given observation site, is also provided. This 
close up takes into account the effect of libration and 'limb shortening'
(optional). A graph of lunar libration for an entire month can be plotted.

There is a choice of either topocentric/geocentric co-ordinates and 
apparent/geometric sunset. Correction for atmospheric refraction is optional.

The program has a built in atlas database which stores latitude and longitude 
data of upto 1000 cities (ships with over 100 cities already entered). 
There are many user-configurable features.




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2. GETTING STARTED
-------------------------------------------------------------------------------

2.1 Minimum system requirements
===============================

The minimum system requirements needed to run MoonCalc are:

* 386 based PC or compatible running DOS (486DX or better recommended)

* One floppy drive (hard drive strongly recommended)

* at least 500K free on disk for temporary storage (floppy should not be write 
protected)

* Colour VGA display or better (partial support for CGA, EGA and Hercules 
displays)


2.2 Files included
==================

The following 14 files should be included on the distribution disk or be present 
after unzipping the moonc60.zip archive:

MOONC60.EXE		The main program
DEFAULTS.MC		Stores initial program default values
TOWNS.DAT		Database of town data, can be modified*
STARDATA.DAT	Data of 9025 stars from Yale Brightstar Database 
BRIGHTST.DAT      Data of 1st magnitude stars
MOONFACE.DAT	Data to generate lunar craters
CONSTELN.DAT      Data to generate constellation lines
WORLDMAP.DAT	Data to generate word map
MAGMODEL.DAT	Model data for calculating Magnetic Declination
SVGA256.BGI       Required to display 600x800 and 1024x768 graphics modes
                  (BGI driver copyright Borland Intl.)
MOONC60.BMP		Nice icon for use as windows shortcut
README.TXT		This file!
README.PDF	      Instructions as pdf file (same as readme.txt file but with graphics) 
WHATSNEW.TXT	Lists new features + history of release dates.

The following file is generated by the program:

SCAN.DAT		Temporary file produced by program during scanning.

(* in versions prior to 5.0, this file was called DATA.PTC and had a different
structure)


2.3 Making Backups 
================== 
 
As with all new programs, it is advisable to make backup copies of all the 
files. You should then write protect the original disk and keep it in a safe 
place. Use only the backed up disk. 
 
 
 
2.4 Running MoonCalc on a floppy drive system 
============================================= 
 
DOS
---
Place your disk in, say, drive A. Now make sure you have the A:> prompt 
showing: 
 
A:> 
 
Type MOONC60 <CR> and the program will start with standard graphics mode. 
MOONC60 S <CR> will start program with graphics in 600x800 mode.
MOONC60 H <CR> will start program with graphics in 1024x768 mode.

The floppy should NOT be write protected as MoonCalc will need to access 
the disk for temporary storage. 
 
 
Windows
-------
Place your disk in, say, drive A. Use Windows explorer or File Manager 
to log onto drive A. Then double-click on the MOONC60.EXE file.


2.5 Installing and running MoonCalc on a hard drive system 
========================================================== 

DOS
--- 
Let us assume that your hard drive is called drive C. You should initially make 
a directory called e.g. MOON: 
 
	md c:\moon   <CR> 
 
Put the floppy disc containing the program into drive A. Copy all the files from 
the floppy disc into the MOON directory: 
 
	copy a:*.* c:\moon  <CR> 
 
Ensure that you are logged onto the MOON directory: 
 
	cd c:\moon  <CR> 
 
Now type MOONC60 <CR> and the program will start with standard graphics mode. 
MOONC60 S <CR> will start program with graphics in 600x800 mode.
MOONC60 H <CR> will start program with graphics in 1024x768 mode.

Windows
------- 
MoonCalc may be run in a DOS box under Windows 3.1 or Windows 95/98. This is
the preferred option. You can have a desktop shortcut if you wish. 

When using MoonCalc under Windows make sure that the 'Working' or 'Start in' 
property of the desktop shortcut points to the directory that contains 
the MoonCalc files. This tells MoonCalc where to find the associated 
files.

The 'Cmd line' property of the shortcut should be....
MOONC60    to start program with standard graphics mode (640x480).
MOONC60 S  to start program with graphics in 600x800 mode.
MOONC60 H  to start program with graphics in 1024x768 mode.

The latter two options may not work on all systems and I do not 
recommend the last one unless you have a very good monitor!

 


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3. USING THE PROGRAM
-------------------------------------------------------------------------------


When the program is run the following MAIN MENU is displayed:


                
                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
                I  Moon Calculator                Version 6.0  I
                I  By Dr. Monzur Ahmed      (c) May 93/Oct 01  I
                I                                              I
                I----------------------------------------------I
                I               M A I N   M E N U              I
                I----------------------------------------------I
                I                                              I
                I    1. Summary tables of Moon Data            I
                I    2. Moon position on Starchart (Dec vs RA) I
                I    3. Simulation of Local Sky (Alt vs Azi)   I
                I    4. Close-up of Moon                       I
                I    5. First Crescent Sighting (Global Scan)  I
                I    6. Hijri Calendar Tabulation              I
                I    7. Libration Graph                        I
                I    8. Eclipses                               I
                I    9. Add/ Delete/ Change Atlas Data         I
                I    0. Change Options                         I
                I    X. Exit to DOS                            I
                I                                              I
                I    Use cursor keys or 0-9 to make choice     I
                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII




You may make a choice from this menu either by using the cursor keys to 
highlight the desired option and pressing enter or by pressing 
1,2,3,4,5,6,7,8,9,0 or X directly.


3.1 Option 1. Summary tables of Moon Data
=========================================

When this option is chosen, the following screen will appear: 
 

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII       IIIIIIIIIIIIIIIIIIIIIIIIII
ICurrent Place = BIRMINGHAM                   I       I     ABERDEEN           I
IPress ENTER to accept or type in new place   I       I     ACCRA              I
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII       I     ALGIERS            I
                                                      I     AMSTERDAM          I
NAME OF PLACE ?                                       I     ANKARA             I
                                                      I     ATHENS             I
                                                      I     BAGHDAD            I
                                                      I     BANGKOK            I
                                                      I     BELFAST            I
                                                      I     BERLIN             I
                                                      I     BERNE              I
                                                      I     BIRMINGHAM      << I
                                                      I     BOGOTA             I
                                                      I     BONN               I
                                                      I     BRADFORD           I
                                                      I     BRASILIA           I
                                                      I     BRUSSELS           I
                                                      IIIIIIIIIIIIIIIIIIIIIIIIII
                                                      IIIIIIIIIIIIIIIIIIIIIIIIII
                                                      I  CURSORS & PAGE UP/DN  I
                                                      I     to move pointer    I
                                                      IIIIIIIIIIIIIIIIIIIIIIIIII


Initially, the location has to be entered. The program comes with a built in 
database of about 100 cities (you can add to or modify this database, see 
section 3.9). The places that are already in the database are listed in a 
scrolling window on the right. You can choose a place from the database either 
by highlighting it with the cursor keys and pressing ENTER or by typing the name 
of the place and pressing ENTER. 
 
If you type in the name of a place which is not in the database, the program 
will ask you to enter the latitude, longitude, time zone and height above sea 
level of this place. You will also be asked *if* Summer Time operates at this 
location. (Note that the rules determining *when* Summer Time starts and ends 
can be altered using 'Change Options' from the Main Menu; see section 3.10.3). 
The latitude and longitude of most major towns can be obtained from a good world 
atlas. The time zone of the place is the time difference in hours between the
location and Greenwich.
 
Next, the program will ask you to enter the year, month, date and time (hours, 
min and sec) for which you wish to calculate the position of the moon.

Once all this preliminary information has been entered, the computer will 
display the message 'Calculation in progress..' before showing four tables of 
data (each table occupying a whole screen). 

Press ENTER repeatedly to cycle through the four tables of data:-


3.1.1 Screen 1 of 4
-------------------

Shows data pertaining to current time as entered by the user following the 
instructions above, eg for Birmingham (UK) on 21st Jan 1996 at 14:50 hrs:

  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  I BIRMINGHAM 52:30N 1:55W TZ:0.0 Ht:236m JD:2450103.5        Topo   Refrac ON I
  I Mag Dec:     -4.655 -4d   39m 20s                 Date:    Sun 21 Jan  1996 I
A I Delta T (TD-UT):     0h   01m 02s                 Time:    14h  50m 00s LT  I
  I Apparent Sunrise:    8h   01m 49s LT   Apparent Sunset:    16h  36m 21s LT  I
  I------------------------------------1 of 4-----------------------------------I
  I Moon Alt:    21.816  21d  48m 59s      Moon Azi:  205.118  205d 07m 05s     I
  I Moon Dec:   -12.564 -12d  33m 51s      Moon RA:    21.135  21h  08m 05s     I
  I Sun Alt:     10.523  10d  31m 25s      Sun Azi:   215.843  215d 50m 34s     I
B I Sun Dec:    -19.970 -19d  58m 12s      Sun RA:     20.204  20h  12m 14s     I
  I Rel Alt:     11.293  11d  17m 34s      Rel Azi:   -10.725 -10d  43m 29s     I
  I Elongation:  15.304  15d  18m 13s      Moon Age:   25.99h  1D   2H  0M      I
  I Phase:0.0194  Mag: -5.58  Width:0.59m  Semi-Diam:0.279 Distance:359942.24km I
  I-----------------------------------------------------------------------------I
  I Moon Rise:           8h   06m 14s LT   Azimuth:            110d 44m 44s     I
C I Moon Set:            18h  27m 14s LT   Azimuth:            252d 03m 41s     I
  I Sunrise-Moonrise:    0h   04m 25s      Sunset-Moonset:     1h   50m 52s     I
  I-----------------------------------------------------------------------------I
  I New Moon:            20 Jan  1996      JDE: 2450103.0357   12h  51m 28s TD  I
  I Full Moon:           4  Feb  1996      JDE: 2450118.1658   15h  58m 45s TD  I
D I Perigee:             19 Jan  1996      JDE: 2450102.4638   23h  07m 52s TD  I
  I Apogee:              1  Feb  1996      JDE: 2450115.1561   15h  44m 51s TD  I
  I-----------------------------------------------------------------------------I
E IENTER:More [H]elp +/-:ħMonth DEL/INS:ħDay END/HOME:ħHr DN/UP:ħMin SPACE:Menu I
  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

The screen is divided into 5 areas:

A: Shows name of chosen location, latitude/longitude/time zone/height above sea 
level of chosen location as entered plus the date and time as entered. 'LT' next 
to the time indicates Local Civil Time ('UT' indicates Universal Time). A '*' 
next to LT (not shown in the example above) indicates that one hour has been 
added for Daylight Saving Time/Summer Time. The Julian Day number (JD) of the 
entered date is displayed on the top line. The top right of the screen also 
indicates whether Topocentric (Topo), as shown above, or Geocentric (Geo) co-
ordinates are in use. Also there is an indication of whether there is correction 
for atmospheric refraction (Refrac ON or Refrac OFF).

The Magnetic Declination (Mag Dec) for the entered time/place is shown. Magnetic 
Declination is the direction of magnetic north relative to true north and varies 
with time and location. A positive value indicates that magnetic north is east 
of true north whilst a negative value indicates that magnetic north is west of 
true north. The geomagnetic field model used in MoonCalc 6.0 is most accurate 
between 1995 and 2005 although a value will be shown for years in the range 
1990-2010. 

Delta T is the difference between Terrestrial Dynamical Time (TD) and Universal 
Time (UT). Delta T cannot be predicted accurately for the future but retrospective 
values can be calculated. MoonCalc uses a combination of empirical equations and 
look-up tables to calculate Delta T.

The sunrise and sunset times for the entered date are also shown. The user can 
choose whether to display apparent or geometric sunrise/set - see section  
3.10.13. 


B: The main part of table. Shows the moon/sun altitude, moon/sun azimuth, 
moon/sun declination, moon/sun right ascension, relative altitude, relative 
azimuth, elongation, age of the moon, moon phase, moon magnitude, crescent width 
(Width) in arc minutes, semi-diameter (semi-diam) of moon and earth-moon 
distance for the location, date and time entered by the user.

ALL DISPLAYED ALTITUDES ARE MEASURED TO THE CENTRE OF THE BODY. TO OBTAIN
ALTITUDE TO LOWER LIMB OF MOON, SUBTRACT SEMI-DIAMETER FROM ALTITUDE TO
CENTRE. ALL AZIMUTHS ARE MEASURED CLOCKWISE RELATIVE TO TRUE NORTH (NOT 
MAGNETIC NORTH).


C: Shows the time and direction (azimuth) of moon rise and moon set for that day 
and location. The interval between apparent sunset and moonset and the interval 
between apparent sunrise and moonrise are also shown.


D: Shows the date, time and Julian Ephemeris Day (JDE) of nearest astronomical 
new moon (conjunction), full moon, apogee and perigee. Note that the times have 
'TD' next to them indicating that times are given as Terrestrial Dynamical Time. 
Remember TD is *not* the same as your local time. The difference between TD and 
GMT (or UT) is called Delta T and is currently just over 1 minute. The new/full 
moon times are accurate to a few seconds whilst the apogee/perigee times are 
accurate to a couple of minutes. If perigee occurs near conjunction it may be 
possible to see a younger crescent than usual.


E: Prompt line indicating that you should press.... 

 ENTER to see all 4 tables of data in sequence, 
 H or F1 for help screen (meaning of abbreviations, brief definitions etc), 
 +/- to increase/decrease month, 
 DELETE/INSERT to increase/decrease day, 
 END/HOME to increase/decrease hour, 
 PAGE UP/DOWN to increase/decrease minute and 
 SPACE to return to the main menu.



3.1.2 Screen 2 of 4
-------------------

Shows data pertaining to *sunset* on that day:

  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  I BIRMINGHAM 52:30N 1:55W TZ:0.0 Ht:236m JD:2450103.5        Topo   Refrac ON I
  I Mag Dec:     -4.655 -4d   39m 20s                 Date:    Sun 21 Jan  1996 I
A I Delta T (TD-UT):     0h   01m 02s                 Time:    14h  50m 00s LT  I
  I Apparent Sunrise:    8h   01m 49s LT   Apparent Sunset:    16h  36m 21s LT  I
  I------------------------------------2 of 4-----------------------------------I
  I AT APPARENT SUNSET>                                                         I
  I New Moon Visibility (Yallop/-5,q0.790) A: Easily visible                    I
  I Moon Alt:    12.619  12d  37m 09s      Moon Azi:  229.693  229d 41m 33s     I
B I Sun Alt:     -0.667 -0d   40m 01s      Sun Azi:   237.962  237d 57m 45s     I
  I Rel Alt:     13.286  13d  17m 11s      Rel Azi:    -8.270 -8d   16m 12s     I
  I Elongation:  16.126  16d  07m 34s      Moon Age:   27.77h  1D   3H  46M     I
  I Phase:0.0219  Mag: -5.67  Width:0.66m  Semi-Diam:0.278 Distance:360179.99km I
  I-----------------------------------------------------------------------------I
  I Moon Rise:           8h   06m 14s LT   Azimuth:            110d 44m 44s     I
C I Moon Set:            18h  27m 14s LT   Azimuth:            252d 03m 41s     I
  I Sunrise-Moonrise:    0h   04m 25s      Sunset-Moonset:     1h   50m 52s     I
  I-----------------------------------------------------------------------------I
  I New Moon:            20 Jan  1996      JDE: 2450103.0357   12h  51m 28s TD  I
  I Full Moon:           4  Feb  1996      JDE: 2450118.1658   15h  58m 45s TD  I
D I Perigee:             19 Jan  1996      JDE: 2450102.4638   23h  07m 52s TD  I
  I Apogee:              1  Feb  1996      JDE: 2450115.1561   15h  44m 51s TD  I
  I-----------------------------------------------------------------------------I
E IENTER:More [H]elp +/-:ħMonth DEL/INS:ħDay END/HOME:ħHr DN/UP:ħMin SPACE:Menu I
  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Areas A, C, D and E remain the same.
The data in area B now relates to *local sunset* on the day entered by the user. 
The screen indicates moon altitude, moon azimuth, sun altitude, sun azimuth, 
relative altitude, relative azimuth, elongation, age of the moon, phase, 
magnitude, crescent width, moon semi-diameter and earth-moon distance. 
The above information is useful in assessing the likelihood of visualising the 
new moon after sunset. In fact, the program uses one of several well known moon 
sighting criteria (in the example above Yallop's criterion is being used) 
to predict if the new moon would be visible from the user's location after 
sunset on that day.For more information on crescent sighting criteria, 
see section 3.5.  To change the sighting criterion see section 3.10.6. 

In the example above, the moon's characteristics (in particular altitude and crescent 
width) satisfy Yallop's criterion for visibility- hence the program indicates moon 
should be 'A:easily visible' on 21 Jan 1996 in Birmingham. Enter the above example, go 
to screen 2 and press the INSERT key to go back a day to 20 Jan 1996. You will see 
that on 20 Jan 1996 the moons characteristics do not satisfy Yallop's criterion and so 
the program declares that the moon is 'Not Visible' that evening.



3.1.3 Screen 3 of 4
-------------------
Shows data pertaining to a time that day when the sun is approximately 
5 degrees below the horizon:

  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  I BIRMINGHAM 52:30N 1:55W TZ:0.0 Ht:236m JD:2450103.5        Topo   Refrac ON I
  I Mag Dec:     -4.655 -4d   39m 20s                 Date:    Sun 21 Jan  1996 I
A I Delta T (TD-UT):     0h   01m 02s                 Time:    14h  50m 00s LT  I
  I Apparent Sunrise:    8h   01m 49s LT   Apparent Sunset:    16h  36m 21s LT  I
  I------------------------------------3 of 4-----------------------------------I
  I WHEN SUN IS ~5° BELOW HORIZON>                    Time:    17h  04m 04s LT  I
  I                                            "Best" Time:    17h  25m 38s LT  I
  I Moon Alt:     9.472  9d   28m 21s      Moon Azi:  235.542  235d 32m 33s     I
B I Sun Alt:     -5.002 -5d   00m 09s      Sun Azi:   243.350  243d 21m 02s     I
  I Rel Alt:     14.475  14d  28m 30s      Rel Azi:    -7.808 -7d   48m 29s     I
  I Elongation:  16.354  16d  21m 15s      Moon Age:   28.23h  1D   4H  14M     I
  I Phase:0.0225  Mag: -5.69  Width:0.67m  Semi-Diam:0.277 Distance:360243.50km I
  I-----------------------------------------------------------------------------I
  I Moon Rise:           8h   06m 14s LT   Azimuth:            110d 44m 44s     I
C I Moon Set:            18h  27m 14s LT   Azimuth:            252d 03m 41s     I
  I Sunrise-Moonrise:    0h   04m 25s      Sunset-Moonset:     1h   50m 52s     I
  I-----------------------------------------------------------------------------I
  I New Moon:            20 Jan  1996      JDE: 2450103.0357   12h  51m 28s TD  I
D I Full Moon:           4  Feb  1996      JDE: 2450118.1658   15h  58m 45s TD  I
  I Perigee:             19 Jan  1996      JDE: 2450102.4638   23h  07m 52s TD  I
  I Apogee:              1  Feb  1996      JDE: 2450115.1561   15h  44m 51s TD  I
  I-----------------------------------------------------------------------------I
E IENTER:More [H]elp +/-:ħMonth DEL/INS:ħDay END/HOME:ħHr DN/UP:ħMin SPACE:Menu I
  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Again areas A, C, D and E are unchanged.
Area B now shows data when the geocentric altitude of the sun is 5 degrees 
below the horizon. At this time the sky is sufficiently dark to optimise the 
likelihood of seeing a new moon. The time when the sun is 5 degrees below the 
horizon is shown together with moon altitude, moon azimuth, sun altitude, sun 
azimuth, relative altitude, relative azimuth, elongation, age of the moon, 
phase, magnitude, crescent width, moon semi-diameter and earth-moon distance. In 
the example shown above, the observer should look for the new moon after sunset 
at about 17:04. The crescent moon should be seen in the western sky (azimuth 
235.5 degrees). The moon will be about 28.2 hours old and will be about 9-10 
degrees above the horizon (moon altitude 9.47 degrees). 

Note that "best time" is also shown (if the moon sets after the sun).
Best time is "sunset + 4/9*lag". This simple rule was derived by Yallop (ref 24)
from the work of Bruin (ref 10, also see section 3.5.1).


3.1.4 Screen 4 of 4
-------------------

This screen shows Hijri calendar data:


  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  I BIRMINGHAM 52:30N 1:55W TZ:0.0 Ht:236m JD:2450103.5        Topo   Refrac ON I
  I Mag Dec:     -4.655 -4d   39m 20s                 Date:    Sun 21 Jan  1996 I
A I Delta T (TD-UT):     0h   01m 02s                 Time:    14h  50m 00s LT  I
  I Apparent Sunrise:    8h   01m 49s LT   Apparent Sunset:    16h  36m 21s LT  I
  I------------------------------------4 of 4-----------------------------------I
  I HIJRI CALENDAR DATA>           Criterion: Yallop/-5 [A or B]                I
  I                                                                             I
  I 1 Ramadhan 1416 AH             starts at sunset on:        21 Jan  1996     I
B I                                & ends at sunset on:        22 Jan  1996     I
  I Hijri Day Number:    501666                                                 I
  I Islamic Lunation No: 16989             Astronomical Lunation No: 904        I
  I Crescent first seen: 21 Jan  1996      [L]ocal or [T]rizonal dates for year I
  I-----------------------------------------------------------------------------I
  I Moon Rise:           8h   06m 14s LT   Azimuth:            110d 44m 44s     I
C I Moon Set:            18h  27m 14s LT   Azimuth:            252d 03m 41s     I
  I Sunrise-Moonrise:    0h   04m 25s      Sunset-Moonset:     1h   50m 52s     I
  I-----------------------------------------------------------------------------I
  I New Moon:            20 Jan  1996      JDE: 2450103.0357   12h  51m 28s TD  I
  I Full Moon:           4  Feb  1996      JDE: 2450118.1658   15h  58m 45s TD  I
D I Perigee:             19 Jan  1996      JDE: 2450102.4638   23h  07m 52s TD  I
  I Apogee:              1  Feb  1996      JDE: 2450115.1561   15h  44m 51s TD  I
  I-----------------------------------------------------------------------------I
E IENTER:More [H]elp +/-:ħMonth DEL/INS:ħDay END/HOME:ħHr DN/UP:ħMin SPACE:Menu I
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Areas A, C, D and E remain the same.
Area B shows Hijri calendar data. The Hijri date is calculated using predicted 
lunar visibility for the user's location. In the above example, Yallop's 
criterion is being used to calculate Hijri data. However, any of the 13 
moonsighting criteria that MoonCalc currently supports may be used (see 3.5.1 
and 3.10.6) making MoonCalc the most accurate and versatile Hijri date converter 
available.

***************************************************************
* Please note that the RGO 67 criterion as implemented in     *
* MoonCalc is not suitable for general Hijri date conversions.*
* (The criterion is suitable for determining the location     *
* of *earliest* crescent visibility on a global scan).        *
***************************************************************
 
In the above example, for Birmingham, 1st Ramadhan 1416 AH begins at sunset on 
21st Jan 1996 and ends at sunset on 22nd Jan 1996. The corresponding Hijri day 
number is 501666 and Islamic lunation number is 16989. The Gregorian date on 
which the crescent is first seen for that month is also displayed.

1 Muharram 1AH is taken to begin at sunset on 15th July 622 CE and end at sunset 
on 16th July 622 CE. The Hijri day number uses sunset 15th July 622 CE as the 
epoch (day 1). Islamic lunation number is the number of lunations that have 
elapsed since Muharram 1 AH (lunation 1).

Pressing 'L' gives a local Hijri calendar for a whole year. Pressing 'T' gives a
Trizonal calendar for a whole year. There is more information on local and 
Trizonal Hijri calendars in section 3.6.1 and 3.6.2.

In any of these 4 screens it is possible to see the data for the next/previous 
month, day, hour or minute using the following keys:


+/-			increase/ decrease MONTH	
DEL/INS		increase/ decrease DAY	
END/HOME		increase/ decrease HOUR	
PAGE DN/UP		increase/ decrease MINUTE	


********************************************************************
*           REMEMBER THE ABOVE KEY COMBINATIONS                    *
*    They are conveniently situated on most standard keyboards     *
*          They are consistent throughout the program              *   
********************************************************************



3.1.5 Earliest new moon sighting for a given location
-----------------------------------------------------

To find the date and time of earliest sighting of the new moon for a given 
location, use the following steps:

* Choose option 1 from Main Menu and enter the name and details of the location 
in question.

* Enter a date near the time of interest and obtain the date of the 
 astronomical new moon (also known as date of conjunction).
	
* Go back to the Main Menu, choose option 1 again and enter this date.
 	
* Go to screen 2 of 4 which shows the data at local sunset.
	
* The program will probably say that moon is 'Not visible' or 'Moon not new' 
('Moon not new' means that the moon is over 7 days old and implies that it 
should be visible)
	
* Use the DEL/INS key to 'hunt' around this date until the earliest date when 
moon 'Should be visible' is obtained.
	
* Now go to screen 3 of 4 to obtain the data for when the sun is 5 degrees below 
the horizon i.e. the optimum time of sighting, azimuth etc.
  
* To get the information for the following month, go back to Screen 2 of 4 and 
press the '+' key to jump forward one lunar month. Again 'hunt' with the DEL/INS 
keys to obtain date of earliest sighting. Now go to screen 3 of 4 as before.
 
It may sound complicated but after a while you will find the procedure 
straightforward.

Alternatively, just go straight to screen 4 of 4 which performs the above 
steps automatically and shows the date when the previous new crescent would 
have been seen for the first time from you location (using the visibility 
criterion that you have chosen).


3.2 Option 2. Moon position on Starchart (Dec vs RA)
====================================================

When this option is chosen, you will be required to enter the date and time. 
This option produces a star chart (a graph of Declination Angle versus Right 
Ascension) and plots the positions of the moon, sun and planets on it. The 
ecliptic is shown as a red line.

The positional data for the stars were obtained from the Yale Brightstar 
Database. The first magnitude stars are labelled using the first 3 letters of 
their common names. NB Pol is Pollux not Polaris (Pole Star)!

COMMON NAME       MAG
----------------------
Sirius,          -1.46
Canopus,         -0.72
Alpha Centuri,   -0.27
Arcturus,        -0.04
Vega,             0.03
Capella,          0.08
Rigel,            0.12
Procyon,          0.38
Achernar,         0.46
Betelgeuse,       0.50
Hadar,            0.61
Altair,           0.77
Acrux,            0.83
Aldebaran,        0.85
Antares,          0.96
Spica,            0.98
Pollux,           1.14
Fomalhaut,        1.16
Deneb,            1.25
Becrux,           1.25
Regulus,          1.35

The planetary positions are also plotted and labelled:

Me			Mercury
V			Venus
M			Mars
J			Jupiter
S			Saturn
U			Uranus
N			Neptune
P			Pluto [position not accurate for dates before 1890 CE]


You can view and label the constellations. The constellation lines are based 
on information in Patrick Moore's Guinness Book of Astronomy (4th edition)
(ref 34) which in turn refers to the Cambridge Sky Catalogues (1987). The
3 letter abbreviations for the constellations are as follows:

ANDROMEDA = And		ANTLIA = Ant		APUS = Aps
AQUARIUS = Aqr		AQUILA = Aql		ARA = Ara
ARIES = Ari			AURIGA = Aur		BOOTES = Boo
CAELUM = Cae		CAMELOPARDUS = Cam	CANCER = Cnc
CANES VENATICI CVn	CANIS MAJOR = Cma		CANIS MINOR = CMi
CAPRICORN = Cap		CARINA = Car		CASSIOPEIA = Cas
CENTAURUS = Cen		CEPHEUS = Cep		CETUS = Cet
CHAMAELEON = Cha		CIRCINUS = Cir		COLUMBA = Col
COMA BERENICES = Com	CORONA AUSTRALIS = CrA	CORONA BOREALIS = CrB
CORVUS = Crv		CRATER = Crt		CRUX AUSTRALIS = Cru
CYGNUS = Cyg		DELPHINUS = Del		DORADO = Dor
DRACO = Dra			EQUULEUS = Eql		ERIDANUS = Eri
FORNAX = For		GEMINI = Gem		GRUS = Gru
HERCULES = Her		HOROLOGIUM = Hor		HYDRA = Hya
HYDRUS = Hyi		INDUS = Ind			LACERTA = Lac
LEO = Leo			LEO MINOR = Lmi		LEPUS = Lep
LIBRA = Lib			LUPUS = Lup			LYNX = Lyn
LYRA = Lyr			MENSA = Men			MICROSCOPIUM = Mic
MONOCEROS = Mon		MUSCA AUSTRALIS = Mus	NORMA = Nor
OCTANS = Oct		OPHIUCHUS = Oph		ORION = Ori
PAVO = Pav			PEGASUS = Peg		PERSEUS = Per
PHOENIX = Phe		PICTOR = Pic		PISCES = Psc
PISCIS AUSTRALIS = PsA	PUPPIS = Pup		PYXIS = Pyx
RETICULUM = Ret		SAGITTA = Sge		SAGITTARIUS = Sgr
SCORPIUS = Sco		SCULPTOR = Scl		SCUTUM = Sct
SERPENS = Ser		SEXTANS = Sxt		TAURAS = Tau
TELESCOPIUM = Tel		TRIANGULUM = Tri		TRIANGULUM AUSTRALE = TrA
TUCANA = Tuc		URSA MAJOR = Uma		URSA MINOR = UMi
VELA = Vel			VIRGO = Vir			VOLANS = Vol
VULPECULA = Vul


The bright limb angle, phase, Right Ascension and Declination of the moon and 
Right Ascension and Declination of the sun are also depicted.

Once the starchart is drawn, the following keys apply:
	
C:			Draw/remove major constellation lines	
L:			Label/unlabel major constellations with standard 3 letter 	
			abbreviation
P:			Print screen to Epson/HP compatible printer	
M/m:			Show more/less stars (i.e. change magnitude)	
SPACE:		Return to main menu	

Also, as before...

+/-			increase/ decrease MONTH	
DEL/INS		increase/ decrease DAY	
END/HOME		increase/ decrease HOUR	
PAGE DN/UP		increase/ decrease MINUTE 




3.3 Option 3. Simulation of Local Sky  (Alt vs Azi)
===================================================

Enter the location and date/time data as usual. The maximum magnitude of stars 
to be displayed is also required. The star database in the program contains data 
for over 9000 stars down to magnitude seven (the lower the magnitude, the 
brighter the star). If you enter a high number for the maximum magnitude, the 
display will show more (and dimmer) stars but will take a long time to generate 
on a slower computer. On a slow machine it is better to view only the brighter 
stars (by specifying maximum magnitude as eg 2 or 3).

The program will now generate a simulation of the sky showing the position of 
the stars and planets. You can toggle between a 'horizon' view and a traditional 
'circular' sky chart. The latter gives a view of the sky as it would appear if 
you were lying on your back with your head facing north and feet facing south. 

The positions of the moon and sun are drawn on this background of stars and planets. 
The moon is drawn in white showing the correct phase and orientation taking into 
account its bright limb angle and parallactic angle. The sun is represented by a 
yellow circle. A printout of the graphical screen can be made if an Epson dot 
matrix or HP Laserjet/Inkjet printer is connected.

Once the sky is drawn, the following keys apply:
	
X/x, Y/y:		  Zoom in/out in the X and Y axes respectively	
Z/z:			  Zoom in/out maintaining current aspect ratio	
Function keys 1-10: 10 Pre-set zooms (zoom factor 1.1 to 3)	
D:			  Set initial default zoom of 1	
Cursors:		  Change direction of view (only in horizon view)	
N,E,S,W		  Change direction of view (only in horizon view)	
P:			  Print screen to Epson/HP compatible printer
C:			  Draw/remove major constellation lines	
L:			  Label/unlabel major constellations with standard 3 letter 
			  abbreviation
A:			  Toggles between cleAn screen & labelled screen
M/m:			  Show more/less stars (i.e. change magnitude)	
V:                  Toggle between horizon view and circular sky view
SPACE:		  Return to main menu	

Other keys which apply but which are not shown at the bottom of the screen are 
the usual:

+/-			  increase/ decrease MONTH	
DEL/INS		  increase/ decrease DAY	
END/HOME		  increase/ decrease HOUR	
PAGE DN/UP		  increase/ decrease MINUTE	
	

We can 'see' the moon and sun setting or rising by increasing /decreasing the 
hour with END/HOME. We can zoom in and out of the central part of the sky using  
X/x, Y/y and Z/z. The function keys will produce images at preset zoom factors 
(Function key1=zoom factor 1.1, Function key 10= zoom factor 3).


3.4 Option 4. Close-up of Moon
==============================

As before, the place and date/time are first entered. A graphical representation 
of a close up of the moon is shown. The phase and orientation of the moon's 
limbs are depicted accurately.

The top left hand part of the screen also shows numeric values of phase, age, 
libration (latitude and longitude), position angle of axis, bright limb angle, 
parallactic angle, selenographic sun latitude, longitude and co-longitude, moon 
altitude and moon azimuth. The libration shown is the total (optical + physical) 
libration and is calculated using methods described by D.H. Eckhardt. 

Some of the above values will change slightly depending on whether MoonCalc is 
set to 'geocentric' or 'topocentric' and also if refraction is on/off (see 
sections 3.10.11 and 3.10.12). Please note that values of certain physical 
parameters of the moon given in the printed Almanac are geocentric. In particular, 
geocentric and topocentric libration may differ by as much as 1 degree. 
Topocentric reduction in the values for libration and position angle of 
axis are made using differential corrections - equations in Explanatory 
Supplement to the Astronomical Ephemeris. See section 3.7 for more information 
on libration.


Again one can increase/decrease the month, day, hour or minute using the key 
combinations below and see the effect on the moon's appearance:

+/-			increase/ decrease MONTH	
DEL/INS		increase/ decrease DAY	
END/HOME		increase/ decrease HOUR	
PAGE DN/UP		increase/ decrease MINUTE	

This feature is especially useful for seeing how the orientation of the moon 
changes hour by hour.

Other keys which apply are:

'C': toggles between 'craters on' and 'craters off'. Switch on the craters 
feature if you have a fast machine (486DX or higher). When this feature is 
switched on, the craters and seas of the near side of the moon are depicted 
graphically taking libration into account.

'N': labels the larger craters/seas (remember 'N' for name)

'G': produces a latitude/longitude grid and shows the mean and apparent centres 
of the disc as well as the rotational and celestial axes.

'L': invokes 'limb shortening' i.e. for very thin crescents the tips of the 
crescent are not visible and so the crescent length is less than 180 degrees, 
sometimes considerably less. Pressing 'L' will not only shorten the crescent but 
will also display the approximate visible crescent length in degrees. MoonCalc 
uses algorithms developed from the data of Danjon (1932, 1936) and Schaefer 
(1991,ref 19) to shorten the crescent length.

'P': a printout of the graphical screen can be made if an EPSON compatible 
or HP Laserjet/Inkjet printer is connected.

'SPACE': return to menu.
 

3.5 Option 5. First Crescent Sighting (Global Scan)
===================================================

MoonCalc is able to predict the areas of the world where the young crescent moon 
is likely to be initially seen using one of several published/well known moon 
sighting criteria. The program will draw a world map and scan the world starting 
at longitude 180W and progress eastwards. The progress of the scan is indicated 
by a dotted yellow line near the top of the screen. The scan is performed in two 
passes (coarse scan first, then fine scan).

You can start scanning either on the day of conjunction or on the following day. 
At each longitude the program will search from a lower latitude (eg 60S) to a 
upper latitude (eg 60N). In other words, the world is divided into a fine grid 
and each intersection on the grid is examined to see if the new moon is visible 
at that location. If the minimum moon visibility criterion is satisfied by that 
location, then the location is marked with a coloured dot - the colour of the 
dot represents the age of the moon at local sunset (see lower right hand corner 
of the output screen for key to these colours). 

At the end of the scan the program will display the location of the place where 
the moon will be first sighted (youngest sighting) as well as the most eastern 
location where the moon will be sighted (most easterly sighting). The location 
of the youngest sighting is usually slightly northwest or southwest of the most 
easterly point. The properties of the moon at the time of local sunset at the 
two points are shown at the bottom of the screen (use Y or E to toggle).

After the scan is complete the following keys apply:

P: 	    printout of display
M: 	    change map layout (flat-full, flat-split, spherical-split)
Cursors:  used to spin spherical map
N:	    remove tilt from spherical map (ie centre on 0 latitude)
C:	    centre spherical map (ie centre on 0 longitude)
G:        show/hide latitude/longitude grid  
Y:        show data for location of Youngest sighting.
E:        show data for most Easterly sighting.
SPACE:    return to menu

The global scan is a *very* processor intensive procedure and may take a long 
time to complete on slower computers. You can exit at any time during the scan 
by pressing ESC. If during a scan, you think that the scan has already located 
all possible areas where the new moon is likely to be seen you can save time by 
terminating the scan early by pressing any key (except ESC or SPACE). It is 
inadvisable to terminate prematurely if you are using the RGO 67 criterion as 
the visibility zone for this criterion can be discontinuous. The scan can also 
be speeded up by making the initial scan grid less fine (see section 3.10.7 and
3.10.8).



3.5.1 Moon sighting criteria used in MoonCalc
---------------------------------------------

"The computation of the appearance of the new crescent is a very long and 
difficult procedure, the demonstration of which requires long calculations and 
many tables..." Al-Biruni (973-1048 CE)

Since ancient times, astronomers have tried to predict the likelihood of seeing 
the new moon by defining minimum visibility criteria. MoonCalc currently 
supports 13 such criteria. The user can choose the moon visibility criterion to 
be used (see section 3.10.6). The following options exist:


* Babylonian....................Age at sunset>24hrs & Lag>48 mins

In ancient times, using observational data, the Babylonians developed a 
moon sighting criterion where the moon was likely to be visible when the 
sunset to moonset interval was >48mins (ie the difference in RA of sun 
and RA of moon at sunset was >12 degrees) and moon age at sunset was >24 
hours. Although generally attributed to the Babylonians (eg ref 10), recent
studies suggest that this criterion may actually have been developed by 
the ancient Indians.


* Ibn Tariq......................[Alt, Lag]

Muslim astronomers extensively investigated the problems of moon sighting 
especially in the 8th-10th century CE. They developed visibility criteria and 
created tables for calculations. 

MoonCalc currently supports Ibn Tariq's criterion which depends on moon altitude 
at sunset and moonset lag. It is hoped that future versions of MoonCalc will 
support other criteria from this era, eg the criteria of Al-Kwarizmi, Al-Batani, 
Habash and others.


* Fotheringham......................[Alt, Rel Azi]

In 1910 Fotheringham developed a moon visibility criterion based mainly on the 
extensive observational data of Schmidt made at Athens over a period of 20 
years (ref 6). During this time Schmidt had documented the sightability or 
unsightability of many moons.  Using Schmidt's data, Fotheringham plotted a 
scatter diagram of moon's altitude at geometric  sunset versus the difference in 
azimuth (relative azimuth) between the sun and the moon at sunset. A curve was 
drawn separating the 'visible' moons from the 'unsighted' moons. This curve was 
then used to predict the likelihood of sighting young moons - if a new moon's 
alt/rel azi falls above the curve than it should be sightable, if it falls below 
the curve it should not be sightable.


* Maunder..........................[Alt, Rel Azi]

In 1911, Maunder again used Schmidt's data together with a few more 
observations (ref 7). He drew the curve lower than Fotheringham.


* Indian/Schoch....................[Alt, Rel Azi]

The Indian Astronomical Ephemeris used a slightly modified version of the above 
two criteria, drawing the line slightly lower than Maunder (ref 8). The Indian 
criterion was initially developed by Carl Schoch (ref 9).


* Bruin ..........................[Alt, Crescent width]

In 1977 F. Bruin published details of a theoretical moon sighting criterion 
based on crescent width and sun/moon altitude (ref 10). In its original form, the 
criterion was represented by a family of V shaped curves on a graph of relative 
altitude (h+s) versus solar depression (s). Each curve in the family represented 
a certain crescent width. Bruin used 0.5 minutes as the limiting crescent width. 
The curves were meant to indicate the solar depression at which the crescent 
would become visible and also the duration of visibility. The criterion was 
subsequently criticised for making certain erroneous assumptions.

MoonCalc uses a slightly modified version of the Bruin criterion with limiting 
crescent width=0.25 minutes as suggested by Ilyas (1984). The criterion as 
implemented in MoonCalc has been simplified so that it now indicates *if* the 
crescent is visible on a particular evening (and not the duration of 
visibility). 


* Ilyas_A.......................[Alt, Elong]

Ilyas has written extensively on moon sighting and lunar calendars (eg ref 11,12,13 
17 and 18). MoonCalc supports three of Ilyas' best known sighting criteria. The 
first criterion depends on the 'moon's relative altitude at sunset' and the 'sun-
moon elongation at sunset' (ie angular separation between the sun and the moon). 
Again a curve based on observational data was drawn on a graph of moon's elative 
altitude at sunset versus sun-moon elongation at sunset. If the properties of a 
crescent lie above the curve then the crescent should be visible and vice versa. 


* Ilyas_B/modified Babylonian...[Lag, Latitude]

Ilyas' second criterion is a modification of the ancient Babylonian system of 
moonset lag times. However Ilyas compensates for latitude (eg at latitude 0 deg: 
lag 41 min; 30 deg:46 mins, 40 deg:49 mins, 50 deg: 55mins). 


* Ilyas_C.......................[Alt, Rel Azi]

Ilyas' third criterion, described in 1988, is a slight modification of Ilyas_A 
and depends on the moon's relative altitude at sunset and the difference in 
azimuth between the sun and moon at sunset. 


* RGO 67........................[Alt, Elong]

The Royal Greenwich Observatory (which sadly closed recently) produced a series 
of information sheets which tabulated predicted first moon sightings (ref 15). The 
calculations are based on the rule that the best time and place for making the 
earliest sightings are when the moon is vertically above the sun at sunset so 
that their azimuths are equal (ie relative azimuth at sunset=0) and where the 
apparent altitude of the moon at sunset is 10 degrees. If the sky is clear and 
the horizon is flat, sighting should be possible just before the sun reaches a 
geocentric altitude of -5 degrees. The criterion as implemented in MoonCalc is 
useful for finding the earliest location where the new moon is likely to be 
sighted. On a global scan, the criterion does *not* show all areas west of the 
'earliest point' where the crescent will be seen.


* South African Astronomical Observatory (SAAO)....[Alt, Rel Azi]

This is a sighting criterion proposed by Drs. John Caldwell and David Laney of 
the South African Astronomical Observatory (ref 20). The criterion was based 
on published crescent sightings together with a few local sightings from Signal 
Hill. The criterion depends on 'topocentric moon altitude (to lower limb) at 
apparent sunset' and 'difference in azimuth at sunset'. Two lines are drawn on a 
graph of altitude versus relative azimuth. The sightability of a crescent is 
'possible' if above upper line, 'improbable' if between the two line or 
'impossible' if below the lower line. 


* Shaukat..........................[Alt, Crescent width]

This criterion, proposed by Khalid Shaukat and the Committee for Crescent 
Observation, New York, depends on the 'topocentric altitude of the moon (to the 
lower limb) at sunset' and the 'calculated crescent width at sunset'. The 
altitude must be >3.4 degrees at sunset and (alt/12.7) + (crescent width in 
arcmin /1.2)>1. The crescent width is calculated in a slightly non-standard way.
The criterion has undergone successive refinements based on prospectively 
collected observation data.


* Yallop 1997/8.....................[Rel Alt, Crescent Width]

This criterion was developed from the Indian and Bruin criteria by Bernard 
Yallop (formerly of the Royal Greenwich Observatory, Cambridge, UK). It takes 
into account information from 295 published moon (non)sightings compiled by 
Schaefer and Doggett. The criterion depends on a parameter called 'q' which is 
derived from the relative geocentric altitude of the moon (ARCV) and 
topocentric crescent width. This is the default criterion used in MoonCalc.
In the original technical note by Yallop (ref 24), q was derived at 'best time' 
(ie sunset + (4/9)* moonset lag). However, it is not always practical to apply 
the criterion at 'best time' and so MoonCalc allows the criterion to be applied 
at sunset or when the sun is at -5 degrees as well as at 'best time'.

The value of q is stratified to give 6 types of predictions:

A: easily visible
B: visible when atmospheric conditions are perfect
C: may need optical aid to find crescent
D: visible with optical aid only
E: not visible even with optical aids
F: outside Danjon limit

Note that applying the criterion at sunset makes the visibility predictions 
slightly more pessimistic compared to 'best time', and global visibility zones 
are west shifted by about 5 degrees of longitude.
 


* Schaefer 1988.................Not Yet Implemented

B.E. Schaefer has developed a complex theoretical sighting criterion based on 
the idea of Bruin. This criterion apparently takes into account atmospheric 
haziness, aerosol scattering, Rayleigh scattering, ozone absorption etc (see 
refs 16,21 and 22). Despite several publications, this criterion has not yet been 
documented in sufficient detail to implement in MoonCalc.
 

3.6 Option 6. Hijri Calendar Tabulation
=======================================

MoonCalc can tabulate Hijri calendars based on predicted crescent visibility. 
Choosing option 6 from the main menu leads to the following Menu: 


                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
                I  Moon Calculator                Version 6.0  I
                I  By Dr. Monzur Ahmed      (c) May 93/Oct 01  I
                I                                              I
                I----------------------------------------------I
                I    H I J R I   C A L E N D A R   M E N U     I
                I----------------------------------------------I
                I                                              I
                I                                              I
                I         1. Local Calendar                    I
                I         2. Trizonal Calendar (text mode)     I
                I         3. Trizonal Calendar (map mode)      I
                I         X. Exit to Main Menu                 I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I    Use cursor keys or 1-3 to make choice     I
                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII


3.6.1 Local Calendar
--------------------

On choosing this option, we are asked to enter a location and date. The program
then produces a table showing a local Hijri calendar based on predicted crescent 
visibility specific for the chosen location; eg for Birmingham, UK:

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I BIRMINGHAM 52:30N 1:55W TZ:0.0 Ht:236m                                      I
I LOCAL HIJRI CALENDAR BASED ON PREDICTED CRESCENT VISIBILITY                 I
I                                                                             I
I Hijri month              Greogorian date   Hijri Day   Islamic Lunation     I
I                                                                             I
I 1 Rajab 1422 AH            19 Sep  2001      503733      17059              I
I 1 Shaban 1422 AH           19 Oct  2001      503763      17060              I
I 1 Ramadhan 1422 AH         17 Nov  2001      503792      17061              I
I 1 Shawwal 1422 AH          17 Dec  2001      503822      17062              I
I 1 Zul-Qida 1422 AH         16 Jan  2002      503852      17063              I
I 1 Zul-Hijja 1422 AH        14 Feb  2002      503881      17064              I
I 1 Muharram 1423 AH         16 Mar  2002      503911      17065              I
I 1 Safar 1423 AH            15 Apr  2002      503941      17066              I
I 1 Rabi Al-Awal 1423 AH     14 May  2002      503970      17067              I
I 1 Rabi Al-Thani 1423 AH    13 June 2002      504000      17068              I
I 1 Jumad Al-Ula 1423 AH     12 July 2002      504029      17069              I
I 1 Jumad Al-Thani 1423 AH   10 Aug  2002      504058      17070              I
I                                                                             I
I 1st day of Hijri months end at sunset on Gregorian dates shown.             I
I Criterion: Yallop/BT [A or B]                                               I
I                                                                             I
I                                                                             I
I [M]ore, Space: Menu                Data from MoonCalc 6.0, (c) Monzur Ahmed I
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

In this example, Yallop's criterion (applied at "Best Time") is being used to 
predict crescent visibility. You can choose any of the supported criteria to predict
crescent visibility - see section 3.10.6. The Gregorian dates corresponding to the 
start of the Hijri months are shown. In addition the Hijri day number and Islamic 
lunation number are listed. In the above example, 1st Rajab 1422 AH (after Hijra) 
occurs on 19th September 2001, the crescent being sightable in Birmingham on the 
evening of 18th September 2001.


3.6.2 Trizonal Calendar (text mode)
-----------------------------------

For practical purposes, the world can be divided into 3 main zones with a 
Hijri calendar for each of the 3 zones. The 3 zones are:

1. Zone A (west)- North, Central and South America, Canada etc
2. Zone B (central) - Europe, Africa, Middle East etc
3. Zone C (east)- India, Pakistan, Bangladesh, Malaysia, China, Indonesia, Australia etc 

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
I TRIZONAL HIJRI CALENDAR BASED ON PREDICTED CRESCENT VISIBILITY              I
I                                                                             I
I Hijri month                    Zone A           Zone B          Zone C      I
I                                (West)          (Central)        (East)      I
I                                                                             I
I 1 Rajab 1422 AH              18 Sep  2001    19 Sep  2001    19 Sep  2001   I
I 1 Shaban 1422 AH             18 Oct  2001    18 Oct  2001    19 Oct  2001   I
I 1 Ramadhan 1422 AH           16 Nov  2001    17 Nov  2001    17 Nov  2001   I
I 1 Shawwal 1422 AH            16 Dec  2001    17 Dec  2001    17 Dec  2001   I
I 1 Zul-Qida 1422 AH           15 Jan  2002    15 Jan  2002    15 Jan  2002   I
I 1 Zul-Hijja 1422 AH          14 Feb  2002    14 Feb  2002    14 Feb  2002   I
I 1 Muharram 1423 AH           15 Mar  2002    16 Mar  2002    16 Mar  2002   I
I 1 Safar 1423 AH              14 Apr  2002    14 Apr  2002    15 Apr  2002   I
I 1 Rabi Al-Awal 1423 AH       14 May  2002    14 May  2002    14 May  2002   I
I 1 Rabi Al-Thani 1423 AH      12 June 2002    13 June 2002    13 June 2002   I
I 1 Jumad Al-Ula 1423 AH       11 July 2002    12 July 2002    12 July 2002   I
I 1 Jumad Al-Thani 1423 AH     10 Aug  2002    10 Aug  2002    10 Aug  2002   I
I                                                                             I
I 1st day of Hijri months end at sunset on Gregorian dates shown.             I
I Criterion: Yallop/BT [A or B]                                               I
I                                                                             I
I                                                                             I
I [M]ore, Space: Menu                Data from MoonCalc 6.0, (c) Monzur Ahmed I
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

As you can see from the above example, the dates for the 3 zones vary slightly.
This is because the Hijri calendar is based on crescent visibility and generally the 
new crescent is not seen from all locations on the same evening. Usually it takes 
at least two days for the crescent to be visible from all regions.

In this example, 1st Rajab 1422 AH occurs on 18th September 2001 for Zone A and 
19th Sept for Zones B and C. The implication is that the crescent was sightable 
after sunset on the evening of 17th September in Zone A and 18th Sept in Zones B and C.

The trizonal calendar is an approximation. All countries within a zone will not 
necessarily see the new crescent on the same day but the crescent will be visible 
from at least a part of the zone on the day indicated. 

Technical note: MoonCalc chooses a "sampling point" in the mid-western region of 
each of the three zones and calculates crescent visibility for that point. If the 
new crescent is visible at this point on date X, then this date is applied to the 
entire zone. The co-ordinates of the three "sampling points" are:

Zone A- latitude 20N, longitude 150W
Zone B- latitude 20N, longitude 15W
Zone C- latitude 0, longitude 100E


3.6.3 Trizonal Calendar (map mode)
----------------------------------

The calendar generated is the same as in 3.6.2 but the output is in graphic rather 
then text format. A map of the world is shown with the three zones marked out 
approximately.



3.7 Option 7. Libration Graph 
=============================

Optical libration is the apparent oscillations of the moon due to the variations in 
the geometric position of the Earth relative to the lunar surface during the 
course of the orbital motion of the moon. Physical libration is the actual 
rotational motion of the moon about its mean rotation. Physical libration is much 
smaller than optical libration and can never be larger than 0.04 degrees in both 
latitude and longitude.

This option draws a graph showing TOTAL libration in latitude versus TOTAL libration 
in longitude for a whole month. The user can choose either topocentric or 
geocentric libration (see 3.10.11). The dates are labelled on the graph at intervals 
of 5 days. The square points on the graph represent midnight. At the bottom the screen, 
the corresponding daily phases of the moon for the month are drawn.  

The libration graph is useful for seeing at a glance the days of maximum libration in 
a particular month thus facilitating observation of "far-side" lunar features.


3.8 Option 8. Eclipses
======================

"To witness a total eclipse of the Sun is a privilege that comes to but few 
people. Once seen, however, it is a phenomenon never to be forgotten.... There 
is something in it all that affects even the strongest nerves and it is almost 
with a sigh of relief that we hail the return of the friendly Sun."  
Isabel M. Lewis, 1924, A Handbook of Solar Eclipses

Version 5 of MoonCalc (and higher) provides data on lunar and solar eclipses.
First, enter the year in question. MoonCalc will then list all the lunar and 
solar eclipses in that year, together with the characteristics of the respective 
eclipses.

I should like to develop this aspect of MoonCalc further in future versions, eg 
have world maps showing zones of totality for solar eclipses, show graphic 
simulations of solar and lunar eclipses etc.


3.9 Option 9. Add/ Delete/ Change/ View Atlas Data
==================================================

The program has a built in database which can store data for up to 1000 cities. 
The program is shipped with over 100 cities already on the database. The 
following pieces of information are stored for each city: 
  
	Name of city 
	Country (optional) 
	Latitude 
	Longitude 
	Time Zone 
	Whether influenced by Summer Time 
	Height above sea level in metres 
 
Choosing this option allows us to make alterations to the ATLAS DATABASE: 

      

                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
                I  Moon Calculator                Version 6.0  I
                I  By Dr. Monzur Ahmed      (c) May 93/Oct 01  I
                I                                              I
                I----------------------------------------------I
                I          A T L A S   D A T A B A S E         I
                I----------------------------------------------I
                I                                              I
                I                                              I
                I              1. Add data                     I
                I              2. Delete data                  I
                I              3. Change data                  I
                I              4. View data                    I
                I              X. Exit to Main Menu            I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I    Use cursor keys or 1-4 to make choice     I
                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII


It is best to add a town to the atlas before using it so as to save time 
inputting latitude/longitude data. 
 
 
3.9.1. Add data 
---------------
Follow the prompts and enter the name of the new location, the country 
optional), the latitude, longitude and time zone. Enter the height of the 
location above sea level (zero if you do not know) and also *whether* summer 
time (British Summer Time/ Daylight Saving Time) should operate. (Note that the 
rules determining *when* Summer Time starts and ends can be altered using 
'Option 10. Change Options' from the Main Menu, see section 3.10.3)
 
Once the location has been entered into the database, it will be saved and the 
name of the location will appear in the scrolling window when option 1,2,3 or 4 
are chosen from the Main Menu. 
		 
 
3.9.2. Delete data 
------------------
Simply type in the name of a location which already exists in the database 
to remove it from the database. Make sure that the spelling is correct 
(although the case does not matter). 
 
 
3.9.3. Change data 
------------------
Type in the name of a location which already exists in the database and follow 
the prompts to alter its properties. 
 
 
3.9.4. View data 
----------------
This generates a table showing all the locations stored in the database in 
alphabetical order. Use Page Up/Down to browse.  
 
 

 
3.10 Option 10. Change Options
==============================

Choosing this item from the main menu takes us to the OPTIONS MENU:  


                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
                I  Moon Calculator                Version 6.0  I
                I  By Dr. Monzur Ahmed      (c) May 93/Aug 01  I
                I                                              I
                I----------------------------------------------I
                I            O P T I O N S    M E N U          I
                I----------------------------------------------I
                I                                              I
                I                                              I
                I         1. Basic Options                     I
                I         2. Advanced Options                  I
                I         X. Exit to Main Menu                 I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I                                              I
                I    Use cursor keys or 1-2 to make choice     I
                IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII


Basic Options
=============
If we choose BASIC OPTIONS, the following screen is displayed:
    
     IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
     I                                                                    I
     I                      CURRENT DEFAULT SETTINGS                      I
     I                                                                    I
     I Default City: BIRMINGHAM                                           I
     I                                                                    I
     I Mode of time entry/display: Local Civil Time (LT)                  I
     I                                                                    I
     I Summer Time, if present, begins on fourth Sunday of month 3        I
     I                          ends on fourth Sunday of month 10         I
     I                                                                    I
     I Monitor Type: Colour                                               I
     I                                                                    I
     I Map Type: Full screen flat map                                     I
     I                                                                    I
     I                                                                    I
     I                                                                    I
     I  Press SPACE to make changes, D for original defaults, ESC to exit I
     IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
     
Pressing 'D' will reset to original factory set defaults.
Pressing the Space Bar allows the user to change the following values which are 
stored as defaults and remembered when the program is next run: 


3.10.1  Default City- usually set to the users home town. 
--------------------
 

3.10.2  Mode of time entry 
--------------------------
Can be set to Local Civil Time (LT) or Universal Time (UT). The former option is 

recommended so that the time that is displayed applies to the user's location.

 
3.10.3  Start and End of Summer Time/Daylight Saving Time
---------------------------------------------------------
The rules for the start and finish of Summer Time or Daylight Saving Time (DST) 
vary from country to country. For example, in 1986 the effective periods for DST 
for various countries were as follows:


===========================================================  
COUNTRY              Effective DST period (dates inclusive)
===========================================================
AUSTRALIA			26 OCT 86	-	28 FEB 86
CANADA			27 APR 86	-	25 OCT 86
FRANCE			30 MAR 86	-	27 SEP 86
IRAQ				01 APR 86	-	30 SEP 86
ITALY				30 MAR 86	-	27 SEP 86
JORDAN			04 APR 86	-	02 OCT 86
SPAIN				30 MAR 86	-	27 SEP 86
SYRIA				16 FEB 86	-	18 OCT 86
TURKEY			30 MAR 86	-	27 SEP 86
USA				27 APR 86	-	25 OCT 86
UK				30 MAR 86	-	25 OCT 86
===========================================================
(NB: for some countries, eg USA, rules may have changed since 1986!)

During DST, one hour (in most countries) is added to the standard time. In many 
countries there are general rules for the start and end of DST. For example, in 
the UK, DST (British Summer Time) usually starts on the fourth Sunday of March 
and ends on the fourth Sunday of October. Similarly, in most areas of the USA, 
DST starts on the first Sunday of April and ends on the last Sunday of October.

The DST handling of the program has been designed to be flexible enough to cater 
for most countries of the world. The start/end of DST can be set either as an 
*absolute* date e.g. 1st May or in a *relative* way e.g. fourth Sunday of March.

Essentially you have to answer 3 questions (following the prompts) to set the 
start or end of DST:

Q1. The month when DST starts or ends.

Q2. The day on which DST starts or ends.
	- for absolute date, choose 'Specific date' for this question.
     	- for relative date, choose a day name e.g. 'Sunday'

Q3. The position of the day in the month.
      - for absolute date, enter the date when you want DST to 
	  start/end.  
      - for relative date, enter the position of the day in the month 
	  i.e. first, second, third, fourth or last. For example if you 
	  want DST to start on the last Sunday of the chosen month, enter 
	  'last'  or if you want DST to start on the fourth Sunday, enter 
	  'fourth'.

Example 1. If you want DST to start on 1st April, the three questions
should be answered as follows:
	Q1. 4
	Q2. Specific date
	Q3. 1

Example 2. If you want DST to start on the last Sunday of April, the 
three questions should be answered as follows:
	Q1. 4
	Q2. Sunday
	Q3. last

The program ships with default start/end of DST valid for the UK i.e. DST starts 
on the fourth Sunday of March and ends on fourth Sunday of October.
 
If the Summer Time/DST rules are different for your location then you must alter 
the rules using this option. If you specify that Summer Time/DST does not apply 
for your location (when you enter the location into the database) then these 
rules will be ignored for that location. 
   

3.10.4  Monitor Type: Colour or Black & White 
-------------------- 


3.10.5 Map Type
---------------
You can choose the type of world map that will be displayed during a global scan 
when the program first runs:

1. Full screen flat map.
2. Split screen flat map showing extra information about the sighting
criterion being used.
3. Split screen spherical map showing extra information about the 
sighting criterion being used.


Advanced Options
================

If you choose ADVANCED OPTIONS from the OPTIONS MENU, the following screen, or one 
similar to it, will appear:

  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  I                                                                    I
  I                  ADVANCED SETTINGS FOR POWER USERS                 I
  I      ONLY MAKE CHANGES IF YOU KNOW EXACTLY WHAT YOU ARE DOING!     I
  I                                                                    I
  I Visibility Criterion:  8 (Ilyas_C...........[Alt, Rel Azi])        I
  I                                                                    I
  I During scan, interval between longitudes:  2 deg                   I
  I During scan, interval between latitudes:   2 deg                   I
  I During scan, lower limit of latitude:     -60 deg                  I
  I During scan, upper limit of latitude:      60 deg                  I
  I                                                                    I
  I [T]opocentric or [G]eocentric: T                                   I
  I Correction for Refraction : Yes                                    I
  I [A]pparent or [G]eometric sunrise/set: A                           I
  I Atmospheric Temperature: 25 Celsius                                I
  I Atmospheric Pressure: 1010 millibars                               I
  I                                                                    I
  I                                                                    I
  I Press SPACE to make changes, D for original defaults, ESC to exit  I
  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII


       				WARNING!
    					********
ONLY MAKE CHANGES TO THESE SETTINGS IF YOU ARE SURE THAT YOU KNOW WHAT YOU ARE 
DOING. OTHERWISE THE PROGRAM MAY PRODUCE SPURIOUS OR MISLEADING RESULTS.
 
Pressing 'D' will reset to factory set defaults. To make changes, press the 
SPACE BAR.


3.10.6 Visibility Criterion
---------------------------

The following screen will appear:


WHICH NEW MOON VISIBILITY CRITERION DO YOU WANT TO USE?

 0. Babylonian....................Age>24 hrs & Lag>48 mins
 1. Ibn Tariq.....................[Alt, Lag]
 2. Fotheringham..................[Alt, Rel Azi]
 3. Maunder.......................[Alt, Rel Azi]
 4. Indian/Schoch.................[Alt, Rel Azi]
 5. Bruin.........................[Alt, Crescent Width]
 6. Ilyas_A.......................[Alt, Elong]
 7. Ilyas_B.......................[Lag, Latitude]
 8. Ilyas_C.......................[Alt, Rel Azi]
 9. RGO 67........................[Alt, (Rel Azi)]
10. SAAO..........................[Alt, Rel Azi]
11. Shaukat.......................[Alt, Crescent Width]
12. Yallop 1997/8.................[Rel Alt, Crescent Width]

The current choice is 8
Press ENTER to accept or type in new default (0-12):


Choose the criterion that you wish to use (option 12, Yallop is the default used 
in the program). See section 3.5.1 for further information on each of these 
criteria.

If criterion number 9 (RGO 67) is chosen, then 2 further choices are provided:

* Minimum moon altitude at apparent sunset
Generally this should be 10 degrees in line with the RGO recommendations. 
However the calculated elongation of the world record moon sighting was 8.1 
degrees (ref 14). The user is allowed to enter a value in the range 0-25 degrees.

* Maximum relative azimuth at sunset
According to RGO sheet 67 the place/time of earliest moon sighting occurs when 
the new moon and sun have the same azimuth at sunset ie relative azimuth is 
zero. When scanning the globe in steps of, say, one or two degrees a relative 
azimuth of zero is too strict. The program allows the user to 'loosen' the 
criterion a little by defining the maximum relative azimuth at sunset which can 
be taken to be zero. (Range allowed 0.001-30 degrees, default: 0.2 degrees, 
recommended: 0.1-0.5 degrees).



3.10.7 Interval between longitudes
----------------------------------
We can define the fineness of the initial grid used for scanning the globe for 
new moon visibility (option 5 from the main menu). The finer the grid the longer 
it will take to complete the scan. This option allows you to set the interval in 
degrees between successive longitudes during the first, coarse scan. Range 
allowed (1-5 degrees). Use 1 degree if you have a fast computer (486DX or 
Pentium). Use higher values if you have a slower computer.


3.10.8 Interval between latitudes
---------------------------------
This option defines the interval between successive latitudes during the first 
scan of the globe. The same comments as for 3.10.7 apply.


3.10.9 Lower limit of latitude
------------------------------
To save time you can define the upper and lower limits of latitude for the 
global scan. Usually a lower limit of -60 degrees (ie 60S) and an upper limit of 
60 degrees (60N) are optimal. Range allowed for lower limit -30 to -90 degrees; 
default -60 degrees.


3.10.10 Upper limit of latitude
-------------------------------
See section 3.10.9. Range allowed for upper limit 30-90 degrees; default 60 
degrees.


3.10.11 Topocentric or Geocentric
---------------------------------
Topocentric = as seen from the observer's place on surface of earth. 
Geocentric = as seen from centre of the earth.
For actual moonsighting, it is usual to choose topocentric.
The *displayed* altitudes are always measured to the centre of the moon/sun 
regardless of topocentric/geocentric setting.


3.10.12 Correction for refraction
---------------------------------
Choose "Yes" if you want to compensate for atmospheric refraction.


3.10.13 Apparent or Geometric sunset
------------------------------------
Apparent sunset: when the upper limb of the sun is on the horizon taking into 
account refraction and parallax.

Geometric sunset: when the centre of the sun is on the horizon NOT taking into 
account refraction or parallax.

Generally this setting should be left on 'Apparent sunset' since this is the 
"usual" definition of sunset used in civil life.
 
For expert users: if you want to calculate such values as ARCV (arc of vision), 
DAZ (difference in azimuth) and ARCL (arc of light) as used in various moon 
sighting criteria, then set sunset to 'Geometric', Topocentric/Geocentric to 
'Geocentric' and Refraction to 'OFF'.... then: 

-relative altitude at sunset = ARCV 
-relative azimuth at sunset = DAZ
-elongation at sunset = ARCL 


3.10.14 Atmospheric Temperature
-------------------------------
The value will effect the internal calculation of refraction. Usually this 
should be set in the range 10-25 degrees Celsius.


3.10.15 Atmospheric Pressure
----------------------------
The value will affect the internal calculation of refraction. Usually this 
should be set to 1010 millibars.



----------------------------------------------------------------------------
4. FUTURE DEVELOPMENTS
----------------------------------------------------------------------------

This is the third full release of MoonCalc. However, the program remains in a 
constant state of development. Please send your suggestions/comments, bug report 
etc to me either by snail mail or by email (see start of document for addresses).

There are many ideas in the pipeline to enhance MoonCalc. However the constraints
of programming in DOS are becoming rather restrictive. I am still working on 
a Windows version of the program. Maybe, one day I may write a Java version.

At present, my primary concern is to remove any bugs from the data generating 
engine. As it stands, the program produces reliable data which is compatible 
with other planetarium type programs and sources.

Generally, the algorithms used in the program are very accurate (based on 
routines in refs 2 and 4 together with several other sources) and are probably 
more accurate than is actually needed by most users.



----------------------------------------------------------------------------
5. ACKNOWLEDGEMENTS
----------------------------------------------------------------------------

I should like to thank the many people who helped in the development and testing 
of this program over the past 8 years. In particular, I should like to thank 
Shakoor Chughtai (UK) for his helpful comments and extensive error testing in early
versions of the program. I am indebted to Omar Afzal (Cornell University, USA) for 
providing me with certain difficult to locate reference materials. My thanks to 
Bernard Yallop (formerly of the Royal Greenwich Observatory, UK) for testing 
MoonCalc and providing friendly advice and stimulating discussions. 

I am grateful to the many, many people who made useful comments on the earlier 
releases of MoonCalc including Rashid Motala, Yusuf Essack, Yaakov Loewinger, 
Geoff Hitchcox, Robert H. van Gent, Ali Cengia, Bob Cripps of The Eastbourne 
Astronomical Society (UK), Paul Gabriel, Martin Lewicki, Tariq Muneer, John Taylor,
Robert H. Douglass, Jean Meeus, Mohammad Ilyas and Ernst Böck. I should also like 
to thank my wife, Sayra, for her support and help with digitising the world map. 

Finally, a special "hello" to my daughters Zahra and Hanifa aged 4.5 and 2 
years respectively when MoonCalc 6.0 was released. They were mainly responsible 
for the delay in the release of the new version :-) 



----------------------------------------------------------------------------
6. DISCLAIMER
----------------------------------------------------------------------------

THIS SOFTWARE AND ACCOMPANYING WRITTEN MATERIALS (INCLUDING INSTRUCTIONS FOR 
USE) ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. FURTHER, THE AUTHOR, 
DOES NOT WARRANT, GUARANTEE, OR MAKE ANY REPRESENTATIONS REGARDING THE USE, OR 
THE RESULTS OF USE, OF THE SOFTWARE OR WRITTEN MATERIALS IN TERMS OF 
CORRECTNESS, ACCURACY, RELIABILITY, CURRENTNESS, OR OTHERWISE. THE ENTIRE RISK 
AS TO THE RESULTS AND PERFORMANCE OF THE SOFTWARE IS ASSUMED BY THE USER.
 
NEITHER THE AUTHOR NOR ANYONE ELSE WHO HAS BEEN INVOLVED IN THE CREATION, 
TESTING OR DELIVERY OF THIS PRODUCT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, 
CONSEQUENTIAL OR INCIDENTAL DAMAGES (INCLUDING DAMAGES FOR LOSS OF BUSINESS 
PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, AND THE LIKE) 
ARISING OUT OF THE USE OR INABILITY TO USE SUCH PRODUCT.
 
	

----------------------------------------------------------------------------
7. GLOSSARY
----------------------------------------------------------------------------

* Astronomical New Moon
The moment when the sun, moon and earth are in one plane (in conjunction).  

* Altitude
The angle up from the horizon. Positive above the horizon, negative below.

* Azimuth
The angle around from the north pole measured on the horizon in the sense NESW
	
* Bright Limb Angle
Difficult to explain without a diagram! Imagine a line joining the tips of the 
two limbs of the bright side of the moon. The BLA is 90 degrees + the 
anticlockwise angle between the celestial north-south axis and the above 
mentioned line. 

* Conjunction
See astronomical new moon.

* Declination
In the equatorial co-ordinate system, the angle measured perpendicular to the 
equator. 

* Elongation
The sun-moon elongation is the angular separation of the moon from the sun as 
observed from a point on earth.

* Latitude
The co-ordinate expressing the angle (north positive, south negative) 
perpendicular to a fundamental plane. On the Earth the geographical 
longitude is the co-ordinate expressing the angle relative to the equator.

* Libration.
Optical Libration: apparent oscillations of the moon due to the variations in 
the geometric position of the Earth relative to the lunar surface during the 
course of the orbital motion of the moon.

Physical libration: actual rotational motion of the moon about its mean 
rotation. Physical libration is much smaller than optical libration and can 
never be larger than 0.04 degrees in both latitude and longitude.

* Longitude
The co-ordinate expressing the angle round from a fixed direction measured in a 
fundamental plane. On the Earth, the geographical longitude is measured with 
respect to the equator.

* Magnetic Declination
The direction of magnetic north relative to true north. If positive, then 
magnetic north is east of true north. Magnetic Declination varies with time and 
location.

* Parallactic angle
The angle clockwise between the observer's zenith axis and the celestial north-
south axis. The parallactic angle will vary with location and time of day. 
Knowledge of both the parallactic angle and the bright limb angle are needed to 
determine the orientation of the moon's limbs as observed in the sky.

* Phase
The area of the disc (of the moon or a planet) which is illuminated.

* Positional angle of axis.
Counterclockwise angle between celestial axis and moon's rotational axis.

* Right Ascension
in the equatorial co-ordinate system the angle measured around from the 
point of Aries in the plane of the equator, in the sense SENW.

* Terrestrial Dynamical Time (TD)
An uniform time scale for accurate calculations defined by atomic clocks (unlike 
Greenwich Mean Time and Universal Time which are based on the Earth's rotation). 
The difference between TD and UT varies with time; currently TD-UT is about 1 
minute.

* Time Zone
Longitudinal strip on the surface of the earth (approx 15 degrees of longitude 
in width) where the zone time is a certain number of hours before or after GMT. 
This time is adopted as the local civil time by national or international 
agreement.



----------------------------------------------------------------------------
8. ABBREVIATIONS USED
----------------------------------------------------------------------------

Alt		Altitude
Azi		Azimuth
BLA		Bright Limb Angle
Dec		Declination
DST		Daylight Saving Time
Elong		Elongation
Geo		Geocentric
GMT		Greenwich Mean Time
hr(s)		Hour(s)
LT		Local Civil Time
Mag Dec     Magnetic Declination
min(s)	Minute(s)
NYI		Not Yet Implemented
RA		Right Ascension
Rel Alt	Relative Altitude
Rel Azi	Relative Azimuth
Semi Diam	Semi-diameter of moon in degrees
sec(s)	Second(s)
TD		Terrestrial Dynamical Time
Topo		Topocentric
TZ		Time Zone
Width		Crescent width in minutes
UT		Universal Time
*		1 hour added for DST/Summer Time



----------------------------------------------------------------------------
9. GENERAL MOON INFORMATION
----------------------------------------------------------------------------

*Distance from Earth:
 centre to centre: mean: 	384,400km
 closest (perigee): 		356,410km
 furthest (apogee): 		406,697km

 surface to surface: mean:	376,284km
 closest (perigee):		348,294km
 furthest (apogee):		398,581km	

*Revolution period: 27.321661 days
*Axial rotation period: 27.321661 days
*Synodic period: 29d 12h 44m 2.9s
*Mean orbital velocity: 3680km/h
*Axial inclination of equator, referred to ecliptic: 1d 32m
*Orbital inclination: 5d 09m
*Orbital eccentricity: 0.0549
*Diameter: 3475.6km
*Apparent diameter seen from Earth:
  max		33m 31s
  min		29m 22s
  mean	31m 5s

*Reciprocal mass, Earth= 1: 81.3
*Mass= 7.35x10^25g
*Mass, Earth= 1: 0.0123
*Volume, Earth=1: 0.0203
*Escape Velocity= 2.38 km/s
*Surface Gravity, Earth= 1:0.1653
*Albedo: 0.07
*Mean magnitude at full moon: -12.7



----------------------------------------------------------------------------
10. FREQUENTLY ASKED QUESTIONS
----------------------------------------------------------------------------

Q. How do I capture and save a MoonCalc map or other MoonCalc graphics screen?
A. The easiest way is to run MoonCalc under Windows. When MoonCalc has produced 
a graphics screen, press the "Print Screen" key (usually next to "Scroll Lock"). 
This captures the image to the clipboard. Next run a graphics program such as 
Paint Shop Pro. "Paste in" the captured image. Then reduce the image to 16 
colours and save as a gif file or bmp file. The above capture trick works for 
resolutions upto 640x480 (i.e. not for 600x800 and 1024x768 modes).

Q. How do I print out MoonCalc data?
A. To printout the tables of data: on some systems running in pure DOS mode, 
pressing the "Print Screen" button should result in a printout. If the program
is running in a DOS box from Windows, pressing "Print Screen" will make a copy 
of the table to the clipboard. Open Windows Notepad and "Paste in" the clipboard
using Control & V. Make sure you are using a monospaced font such as Courier. 
You can now printout the Notepad screen. 
To printout MoonCalc graphics screen: on a pure DOS system pressing 'P' after a
graphics screen has been printed out gives the option of printing out to a 
Epson ar HP Laserjet printer. In Windows mode, you can capture the graphics
as described in the previous question and printout using a program such as Paint
Shop Pro (works for upto 640x480 resolution).

Q. Why are the sunset, sunrise, moonset and moonrise times out by an hour?
A. Either the time zone is entered incorrectly or daylight saving time rules 
have to be changed. The Time Zone that MoonCalc suggests are only approximate.

Q. Why doesn't MoonCalc run properly under Windows 95/8?  
A. Make sure that the "start in:" or "Working directory" property of the 
desktop shortcut to the moonc60.exe file points to the directory containing 
the MoonCalc files.

Q. Why does MoonCalc crash with "runtime error 200" on my fast PC?
A. This should not occur with MoonCalc 5 and higher although it used to occur 
with older version of the program. Basically, the error was due to a bug in the 
compiler used to write MoonCalc which caused an overflow when the program was 
ran on a fast Pentium computer. I have tested version 6.0 on a variety of 
fast PCs without problems.

Q. Why does MoonCalc crash with "runtime error 207" on my PC?
A. This is a erratic problem which seems to be related to the magnetic 
declination routine. I have not got to the bottom of it. Often running the
program again sorts things out. If the error keeps occurring, try moving the
magmodel.dat file out of the working directory - this bypasses the magnetic
declination routines.


----------------------------------------------------------------------------
11. CONCLUSIONS
----------------------------------------------------------------------------

MoonCalc was developed over a period of 8 years and continues to be in a state 
of constant development. The program has given me a lot of pleasure to write and 
I hope very much that you enjoy using MoonCalc and find it useful.

Users of MoonCalc are encouraged to test the various functions of the program 
and compare the data produced by the program with actual sightings of the moon, 
particularly sightings of the crescent moon. All suggestions and comments which 
may improve the program are welcomed.

----------------------------------------------------------------------------
Dr. Monzur Ahmed BSc(Hons), MD, MBChB, MRCP(UK)
49 Kempson Avenue, Birmingham, B72 1HE, UK.

email: monzur@bigfoot.com
	 monz@starlight.demon.co.uk
       
http://www.starlight.demon.co.uk/mooncalc
http://www.ummah.org.uk/ildl/mooncalc.html

10th October 2001
----------------------------------------------------------------------------




----------------------------------------------------------------------------
12. SELECTED REFERENCES
----------------------------------------------------------------------------


Computing and Astronomy
-----------------------

1.  Peter Duffett-Smith, 1992; Practical  Astronomy with your 
Calculator;3rd edition; Cambridge University Press.

2.  Peter Duffett-Smith, 1992; Practical  Astronomy with your Personal 
Computer;2nd edition; Cambridge University Press.

3.  Jean Meeus, 1988; Astronomical Formulae for Calculators; 4th 
edition; Willmann-Bell Inc; Virginia, USA.

4.  Jean Meeus, 1991; Astronomical Algorithms; Willmann-Bell Inc; 
Virginia, USA. [2nd edition came out in 1999]

5.  Montenbruck, O. and Pfleger,T; 1998; Astronomy on the Personal Computer;
3rd edition; Springer-Verlag, Berlin [4th edition now available]


Crescent visibility and lunar calendar
--------------------------------------

6. Fotheringham J.K. On the smallest visible phase of the moon; 
Mon. Not.R. Astron. Soc. (1910),70:527-531.

7. Maunder W. On the smallest visible phase of the moon;
J. British Astron Assoc (1911),21:355-62.

8. Indian Astronomical Ephemeris, 1979, India Meteorology Department,
New Delhi. 

9. Schoch, C. (1930) Tafel fur Neulicht; Ergaenzungsheft zu den 
Astronomischen Nachrichten (1930), 8(2): B17

10. Bruin F. The first visibility of the lunar crescent. Vistas Astron
(1977):21:331-358

11. Mohammad Ilyas; A Modern Guide to Astronomical Calculations of 
Islamic Calendar, Times & Qibla,1984;Berita Publishing Sdn Bhd.; Kuala 
Lumpur, Malaysia

12. Mohammad Ilyas; Astronomy of Islamic Calendar, 1997; A.S Noordeen 
Publishers; Kuala Lumpur, Malaysia.

13. Mohammad Ilyas; New Moon's Visibility and International Islamic 
Calendar(for the Asia-Pacific Region 1407H-1421H), 1994; Published by 
Organisation of Islamic Conference (OIC) Standing Committee on 
Scientific and Technological Co-operation (COMSTECH) and Regional 
Islamic Da'wah Council of South East Asia and Pacific (RISEAP), 
Malaysia.

14. Schaefer B.E., Ahmad I.A. and  Doggett L.; Records for Moon 
Sightings; Q.J. Ast. Soc. (1993), 34:53-56  

15. RGO Astronomical Information Sheet No. 67; Prepared by HM Nautical 
Almanac Office, Royal Greenwich Observatory, Cambridge, UK.
Also sheets 6,50,52,55,56,62,71,72,73,75&76. Most of these sheets were
written by Dr. B.D. Yallop.

16. Schaefer B.E., Visibility of lunar crescent; Q.J R. Ast. Soc. (1988),
29:511-523

17. Ilyas M. Limiting altitude separation in the Moon's first visibility
criterion. Astron Astrophys (1988),206:133-135. 

18. Ilyas M. Lunar Crescent Visibility and Islamic Calendar; 
Q.J.R. Ast. Soc. (1994), 35:425-461.

19. Schaefer B.E., Length of the Lunar Crescent;Q.J.R. Astron. Soc.(1991), 
32:265-277

20. Caldwell J. and Laney D. Young Crescent Visibility Predictions for 1997
(Islamic 1417/1418); South African Astronomical Observatory.

21. Doggett L.E. and Schaefer B.E., Lunar Crescent Visibility; 
Icarus (1994),107:388-403.
  
22. Schaefer B.E., Lunar Crescent Visibility; Q.J.R. Astron. Soc.(1996), 
37:759-768.

23. Pepin M.B., In Quest of the Youngest Moon; Sky & Telescope, 
Dec 1996:104-106. 

24. Yallop B.D., A Method for Predicting the First Sighting of New Moon;
NAO Technical Note No 69; HM Nautical Almanac Office, Royal Greenwich
Observatory, Cambridge, UK; first released June 1997, revised 1998.

25. Fatoohi L.J., Stephenson F.R. and Al-Dargazelli S.S., The Danjon Limit 
of First Visibility of the Lunar Crescent; The Observatory (April 1998), 
118(1143):65-72

26. Eckhardt D.H. Theory of the libration of the moon. Moon and Planets,
(1981) vol 25:3 



Geomagnetism:
-------------
27. Chapman, S., and J. Bartels, Geomagnetism, Oxford Univ. Press 
(Clarendon), London and New York, Volumes 1 and 2, 1940.

28. Langel, R.A., The Main Field, in Geomagnetism, Volume 1, 
J. Jacobs (Editor), Academic Press, 1987.

29. Nelson H.J., L. Hurwitz and D. Knapp, Magnetism of the Earth, 
Publication 40-1 U.S. Department of Commerce, United States Government 
Printing Office, Washington, 1962.

30. Parkinson, W.D., Introduction to Geomagnetism, Scottish Academic 
Press, Edinburgh 1983.



Almanacs & Reference works
--------------------------

31. The Star Almanac for Land Surveyors, HMSO, London.

32. Explanatory Supplement to the Astronomical Ephemeris, London.

33. Multiyear Interactive Computer Almanac (MICA) version 1.5; 1900-2005.
US Naval Observatory; Willmann-Bell Inc; Virginia; USA. 

34. Moore,P.,Guinness Book of Astronomy, 4th ed, Guinness Puplishing, Middlesex, 
UK



Internet
--------

35. Monzur Ahmed, Islamic calendar based on predicted lunar visibility. 
International Lunar Date Lines; 
Internet 1996-2001;  http://www.ummah.org.uk/ildl/
or http://www.starlight.demon.co.uk/ildl/

36. Monzur Ahmed, Regional Islamic Calendar;
Internet 1997-2001;  http://www.ummah.org.uk/ildl/zone3/
or http://www.starlight.demon.co.uk/zone3/

37. Monzur Ahmed, Astronomy and Islam
Internet 1997-2001;  http://www.ummah.org.uk/astronomy/
(Has extensive links to other related sites)
