README 256KB Feb 19 2012 01:21:46 PM

README 256KB Feb 19 2012 01:21:46 PM
Moon Calculator
Version 6.0
Program and documentation by
Dr. Monzur Ahmed
49 Kempson Avenue, Birmingham, B72 1HE, U.K.
[email protected]
[email protected]
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)
MoonCalc 6.0 © Dr Monzur Ahmed
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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
MoonCalc 6.0 © Dr Monzur Ahmed
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0. Copyright
Moon Calculator (MoonCalc), associated data files and this document are copyright (c) by Dr. Monzur Ahmed 19932001. 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 direction 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.
MoonCalc 6.0 © Dr Monzur Ahmed
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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
DEFAULTS.MC
TOWNS.DAT
STARDATA.DAT
BRIGHTST.DAT
MOONFACE.DAT
CONSTELN.DAT
WORLDMAP.DAT
MAGMODEL.DAT
SVGA256.BGI
MOONC60.BMP
README.TXT
README.PDF
WHATSNEW.TXT
The main program
Stores initial program default values
Database of town data, can be modified*
Data of 9025 stars from Yale Brightstar Database
Data of 1st magnitude stars
Data to generate lunar craters
Data to generate constellation lines
Data to generate word map
Model data for calculating Magnetic Declination
Required to display 600x800 and 1024x768 graphics modes
(BGI driver copyright Borland Intl.)
Nice icon for use as windows shortcut
Documentation for MoonCalc in ASCII format
This file!
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.
MoonCalc 6.0 © Dr Monzur Ahmed
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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!
MoonCalc 6.0 © Dr Monzur Ahmed
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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
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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:
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ICurrent Place = BIRMINGHAM
I
IPress ENTER to accept or type in new place
I
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
NAME OF PLACE ?
MoonCalc 6.0 © Dr Monzur Ahmed
IIIIIIIIIIIIIIIIIIIIIIIIII
I
ABERDEEN
I
I
ACCRA
I
I
ALGIERS
I
I
AMSTERDAM
I
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
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I CURSORS & PAGE UP/DN I
I
to move pointer
I
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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:
A
B
C
D
E
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
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
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
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
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
IENTER:More [H]elp +/-:±Month DEL/INS:±Day END/HOME:±Hr DN/UP:±Min 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.
MoonCalc 6.0 © Dr Monzur Ahmed
7 of 36
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:
A
B
C
D
E
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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
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
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
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
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
IENTER:More [H]elp +/-:±Month DEL/INS:±Day END/HOME:±Hr DN/UP:±Min SPACE:Menu I
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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.
MoonCalc 6.0 © Dr Monzur Ahmed
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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:
A
B
C
D
E
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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
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
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
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
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
IENTER:More [H]elp +/-:±Month DEL/INS:±Day END/HOME:±Hr DN/UP:±Min SPACE:Menu I
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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 semidiameter 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).
MoonCalc 6.0 © Dr Monzur Ahmed
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3.1.4 Screen 4 of 4
This screen shows Hijri calendar data:
A
B
C
D
E
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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
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
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
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
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
IENTER:More [H]elp +/-:±Month DEL/INS:±Day END/HOME:±Hr DN/UP:±Min SPACE:Menu I
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
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:
+/DEL/INS
END/HOME
PAGE DN/UP
increase/ decrease MONTH
increase/ decrease DAY
increase/ decrease HOUR
increase/ decrease MINUTE
REMEMBER THE ABOVE KEY COMBINATIONS
THEY ARE CONVENIENTLY SITUATED ON MOST STANDARD KEYBOARDS.
THEY ARE CONSISTENT THROUGHOUT THE PROGRAM
MoonCalc 6.0 © Dr Monzur Ahmed
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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 versus 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.
Starchart: yellow circle=Sun; white disc/crescent= Moon, Me= Mercury, V=Venus, M=Mars, J=Jupiter, S=Saturn,
U=Uranus, N=Neptune, P=Pluto; stars and constellations – see text.
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)!
MoonCalc 6.0 © Dr Monzur Ahmed
11 of 36
COMMON NAME
Sirius
Canopus
Alpha Centuri
Arcturus
Vega
Capella
Rigel
Procyon
Achernar
Betelgeuse
Hadar
Altair
Acrux
Aldebaran
Antares
Spica
Pollux
Fomalhaut
Deneb
Becrux
Regulus
MAGNITUDE
-1.46
-0.72
-0.27
-0.04
0.03
0.08
0.12
0.38
0.46
0.50
0.61
0.77
0.83
0.85
0.96
0.98
1.14
1.16
1.25
1.25
1.35
The planetary positions are also plotted and labelled:
Me
V
M
J
S
U
N
P
Mercury
Venus
Mars
Jupiter
Saturn
Uranus
Neptune
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
AQUARIUS = Aqr
ARIES = Ari
CAELUM = Cae
CANES VENATICI CVn
CAPRICORN = Cap
CENTAURUS = Cen
CHAMAELEON = Cha
COMA BERENICES = Com
CORVUS = Crv
CYGNUS = Cyg
DRACO = Dra
FORNAX = For
HERCULES = Her
HYDRUS = Hyi
LEO = Leo
LIBRA = Lib
LYRA = Lyr
MONOCEROS = Mon
OCTANS = Oct
PAVO = Pav
PHOENIX = Phe
ANTLIA = Ant
AQUILA = Aql
AURIGA = Aur
CAMELOPARDUS = Cam
CANIS MAJOR = CMa
CARINA = Car
CEPHEUS = Cep
CIRCINUS = Cir
CORONA AUSTRALIS = CrA
CRATER = Crt
DELPHINUS = Del
EQUULEUS = Eql
GEMINI = Gem
HOROLOGIUM = Hor
INDUS = Ind
LEO MINOR = Lmi
LUPUS = Lup
MENSA = Men
MUSCA AUSTRALIS = Mus
OPHIUCHUS = Oph
PEGASUS = Peg
PICTOR = Pic
MoonCalc 6.0 © Dr Monzur Ahmed
APUS = Aps
ARA = Ara
BOOTES = Boo
CANCER = Cnc
CANIS MINOR = CMi
CASSIOPEIA = Cas
CETUS = Cet
COLUMBA = Col
CORONA BOREALIS = CrB
CRUX AUSTRALIS = Cru
DORADO = Dor
ERIDANUS = Eri
GRUS = Gru
HYDRA = Hya
LACERTA = Lac
LEPUS = Lep
LYNX = Lyn
MICROSCOPIUM = Mic
NORMA = Nor
ORION = Ori
PERSEUS = Per
PISCES = Psc
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PISCIS AUSTRALIS = PsA
RETICULUM = Ret
SCORPIUS = Sco
SERPENS = Ser
TELESCOPIUM = Tel
TUCANA = Tuc
VELA = Vel
VULPECULA = Vul
PUPPIS = Pup
SAGITTA = Sge
SCULPTOR = Scl
SEXTANS = Sxt
TRIANGULUM = Tri
URSA MAJOR = Uma
VIRGO = Vir
PYXIS = Pyx
SAGITTARIUS = Sgr
SCUTUM = Sct
TAURAS = Tau
TRIANGULUM AUSTRALE = TrA
URSA MINOR = UMi
VOLANS = Vol
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:
L:
P:
M/m:
SPACE:
Draw/remove major constellation lines
Label/unlabel major constellations with standard 3 letter
abbreviation
Print screen to Epson/HP compatible printer
Show more/less stars (i.e. change magnitude)
Return to main menu
Also, as before...
+/DEL/INS
END/HOME
PAGE DN/UP
increase/ decrease MONTH
increase/ decrease DAY
increase/ decrease HOUR
increase/ decrease MINUTE
3.3 Option 3. Simulation of Local Sky (Alt versus 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:
MoonCalc 6.0 © Dr Monzur Ahmed
13 of 36
Sky simulation: horizon view (above), circular view (below); Yellow circle=Sun; white disc/crescent= Moon, Me=
Mercury, V=Venus, M=Mars, J=Jupiter, S=Saturn, U=Uranus, N=Neptune, P=Pluto; stars & constellations – see text
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:
Z/z:
Function keys 1-10: 10
D:
Cursors:
N,E,S,W
P:
C:
Zoom in/out in the X and Y axes respectively
Zoom in/out maintaining current aspect ratio
Pre-set zooms (zoom factor 1.1 to 3)
Set initial default zoom of 1
Change direction of view (only in horizon view)
Change direction of view (only in horizon view)
Print screen to Epson/HP compatible printer
Draw/remove major constellation lines
MoonCalc 6.0 © Dr Monzur Ahmed
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L:
A:
M/m:
V:
SPACE:
Label/unlabel major constellations with standard 3 letter
abbreviation
Toggles between cleAn screen & labelled screen
Show more/less stars (i.e. change magnitude)
Toggle between horizon view and circular sky view
Return to main menu
Other keys which apply but which are not shown at the bottom of the screen are the usual:
+/DEL/INS
END/HOME
PAGE DN/UP
increase/ decrease MONTH
increase/ decrease DAY
increase/ decrease HOUR
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.
Close up of moon: craters can be switched on/off with ‘C’ and labelled/ unlabelled with ‘N’; grid can be switched
on/off with ‘G’; difference between apparent and mean centres reflects libration
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
MoonCalc 6.0 © Dr Monzur Ahmed
15 of 36
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:
+/DEL/INS
END/HOME
PAGE DN/UP
increase/ decrease MONTH
increase/ decrease DAY
increase/ decrease HOUR
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). The map can be displayed in three ways:
MoonCalc 6.0 © Dr Monzur Ahmed
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Global scan: standard flat map (top), split screen with flat map (left); split screen with spherical map (right). Toggle
between the three by pressing ‘M’
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:
M:
Cursors:
N:
C:
G:
Y:
E:
SPACE:
printout of display
change map layout (flat-full, flat-split, spherical-split)
used to spin spherical map
remove tilt from spherical map (ie centre on 0 latitude)
centre spherical map (ie centre on 0 longitude)
show/hide latitude/longitude grid
show data for location of Youngest sighting.
show data for most Easterly sighting.
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
MoonCalc 6.0 © Dr Monzur Ahmed
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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, AlBatani, 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).
MoonCalc 6.0 © Dr Monzur Ahmed
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• 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
MoonCalc 6.0 © Dr Monzur Ahmed
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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.
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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
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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
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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:
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
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
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I 1 Zul-Qida 1422 AH
16 Jan 2002
503852
17063
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I 1 Zul-Hijja 1422 AH
14 Feb 2002
503881
17064
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I 1 Muharram 1423 AH
16 Mar 2002
503911
17065
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I 1 Safar 1423 AH
15 Apr 2002
503941
17066
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I 1 Rabi Al-Awal 1423 AH
14 May 2002
503970
17067
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I 1 Rabi Al-Thani 1423 AH
13 June 2002
504000
17068
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I 1 Jumad Al-Ula 1423 AH
12 July 2002
504029
17069
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I 1 Jumad Al-Thani 1423 AH
10 Aug 2002
504058
17070
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I 1st day of Hijri months end at sunset on Gregorian dates shown.
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I Criterion: Yallop/BT [A or B]
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I [M]ore, Space: Menu
Data from MoonCalc 6.0, (c) Monzur Ahmed I
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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
MoonCalc 6.0 © Dr Monzur Ahmed
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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
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I TRIZONAL HIJRI CALENDAR BASED ON PREDICTED CRESCENT VISIBILITY
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I Hijri month
Zone A
Zone B
Zone C
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(West)
(Central)
(East)
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I 1 Rajab 1422 AH
18 Sep 2001
19 Sep 2001
19 Sep 2001
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I 1 Shaban 1422 AH
18 Oct 2001
18 Oct 2001
19 Oct 2001
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I 1 Ramadhan 1422 AH
16 Nov 2001
17 Nov 2001
17 Nov 2001
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I 1 Shawwal 1422 AH
16 Dec 2001
17 Dec 2001
17 Dec 2001
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I 1 Zul-Qida 1422 AH
15 Jan 2002
15 Jan 2002
15 Jan 2002
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I 1 Zul-Hijja 1422 AH
14 Feb 2002
14 Feb 2002
14 Feb 2002
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I 1 Muharram 1423 AH
15 Mar 2002
16 Mar 2002
16 Mar 2002
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I 1 Safar 1423 AH
14 Apr 2002
14 Apr 2002
15 Apr 2002
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I 1 Rabi Al-Awal 1423 AH
14 May 2002
14 May 2002
14 May 2002
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I 1 Rabi Al-Thani 1423 AH
12 June 2002
13 June 2002
13 June 2002
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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
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I 1st day of Hijri months end at sunset on Gregorian dates shown.
I
I Criterion: Yallop/BT [A or B]
I
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I [M]ore, Space: Menu
Data from MoonCalc 6.0, (c) Monzur Ahmed I
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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
MoonCalc 6.0 © Dr Monzur Ahmed
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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.
Tri-zonal calendar – the 3 zones are indicated by the coloured ellipses
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).
Libration graph: 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.
MoonCalc 6.0 © Dr Monzur Ahmed
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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.
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IYear: 2001
I
I
I
ISolar Eclipses:
I
I Max eclipse: 21 June 2001
12:05 TD
central, total
I
I Max eclipse: 14 Dec 2001
20:53 TD
central, annular
I
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ILunar Eclipses:
I
I Max eclipse: 9 Jan 2001
20:22 TD
umbral, mag 1.186
I
I Max eclipse: 5 July 2001
14:57 TD
umbral, mag 0.492
I
I Max eclipse: 30 Dec 2001
10:30 TD
penumbral, mag 0.884
I
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Data from MoonCalc 6.0, (c) Monzur Ahmed I
I-----------------------------------------------------------------------------I
IENTER:Another year SPACE:Main Menu
I
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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:
MoonCalc 6.0 © Dr Monzur Ahmed
24 of 36
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I Moon Calculator
Version 6.0 I
I By Dr. Monzur Ahmed
(c) May 93/Oct 01 I
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A T L A S
D A T A B A S E
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1. Add data
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2. Delete data
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3. Change data
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4. View data
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X. Exit to Main Menu
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Use cursor keys or 1-4 to make choice
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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.
MoonCalc 6.0 © Dr Monzur Ahmed
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3.10 Option 10. Change Options
Choosing this item from the main menu takes us to the OPTIONS MENU:
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I Moon Calculator
Version 6.0 I
I By Dr. Monzur Ahmed
(c) May 93/Aug 01 I
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O P T I O N S
M E N U
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1. Basic Options
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2. Advanced Options
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X. Exit to Main Menu
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Use cursor keys or 1-2 to make choice
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Basic Options
If we choose BASIC OPTIONS, the following screen is displayed:
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CURRENT DEFAULT SETTINGS
I
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I Default City: BIRMINGHAM
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I Mode of time entry/display: Local Civil Time (LT)
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I Summer Time, if present, begins on fourth Sunday of month 3
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ends on fourth Sunday of month 10
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I Monitor Type: Colour
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I Map Type: Full screen flat map
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I Press SPACE to make changes, D for original defaults, ESC to exit I
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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.
MoonCalc 6.0 © Dr Monzur Ahmed
26 of 36
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.
MoonCalc 6.0 © Dr Monzur Ahmed
27 of 36
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:
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ADVANCED SETTINGS FOR POWER USERS
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ONLY MAKE CHANGES IF YOU KNOW EXACTLY WHAT YOU ARE DOING!
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I Visibility Criterion: 8 (Ilyas_C...........[Alt, Rel Azi])
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I During scan, interval between longitudes: 2 deg
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I During scan, interval between latitudes:
2 deg
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I During scan, lower limit of latitude:
-60 deg
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I During scan, upper limit of latitude:
60 deg
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I [T]opocentric or [G]eocentric: T
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I Correction for Refraction : Yes
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I [A]pparent or [G]eometric sunrise/set: A
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I Atmospheric Temperature: 25 Celsius
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I Atmospheric Pressure: 1010 millibars
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I Press SPACE to make changes, D for original defaults, ESC to exit I
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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.
MoonCalc 6.0 © Dr Monzur Ahmed
28 of 36
3.10.6 Visibility Criterion
The following screen will appear:
WHICH NEW MOON VISIBILITY CRITERION DO YOU WANT TO USE?
0.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Babylonian....................Age>24 hrs & Lag>48 mins
Ibn Tariq.....................[Alt, Lag]
Fotheringham..................[Alt, Rel Azi]
Maunder.......................[Alt, Rel Azi]
Indian/Schoch.................[Alt, Rel Azi]
Bruin.........................[Alt, Crescent Width]
Ilyas_A.......................[Alt, Elong]
Ilyas_B.......................[Lag, Latitude]
Ilyas_C.......................[Alt, Rel Azi]
RGO 67........................[Alt, (Rel Azi)]
SAAO..........................[Alt, Rel Azi]
Shaukat.......................[Alt, Crescent Width]
Yallop 1997/8.................[Rel Alt, Crescent Width]
The current choice is 12
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.
MoonCalc 6.0 © Dr Monzur Ahmed
29 of 36
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.
MoonCalc 6.0 © Dr Monzur Ahmed
30 of 36
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.
MoonCalc 6.0 © Dr Monzur Ahmed
31 of 36
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 (approximately 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.
MoonCalc 6.0 © Dr Monzur Ahmed
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8. Abbreviations Used
Alt
Azi
BLA
Dec
DST
Elong
Geo
GMT
hr(s)
LT
Mag Dec
min(s)
NYI
RA
Rel Alt
Rel Azi
Semi Diam
sec(s)
TD
Topo
TZ
Width
UT
*
Altitude
Azimuth
Bright Limb Angle
Declination
Daylight Saving Time
Elongation
Geocentric
Greenwich Mean Time
Hour(s)
Local Civil Time
Magnetic Declination
Minute(s)
Not Yet Implemented
Right Ascension
Relative Altitude
Relative Azimuth
Semi-diameter of moon in degrees
Second(s)
Terrestrial Dynamical Time
Topocentric
Time Zone
Crescent width in minutes
Universal Time
1 hour added for DST/Summer Time
9. General Moon Information
•
Distance from Earth:
centre to centre: mean:
closest (perigee):
furthest (apogee):
surface to surface: mean:
closest (perigee):
furthest (apogee):
384,400km
356,410km
406,697km
376,284km
348,294km
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
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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 mono-spaced 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 or 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 up to 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:
[email protected]
[email protected]
http://www.starlight.demon.co.uk/mooncalc
http://www.ummah.org.uk/ildl/mooncalc.html
10th October 2001
MoonCalc 6.0 © Dr Monzur Ahmed
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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 1407H1421H), 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.
MoonCalc 6.0 © Dr Monzur Ahmed
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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 Publishing, 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)
MoonCalc 6.0 © Dr Monzur Ahmed
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