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MOON CALCULATOR Version 4.0 Program & documentation by Dr. Monzur Ahmed 27 Poplar Rd, Birmingham, B11 1UH, U.K. Email: monz@starlight.demon.co.uk Homepages: http://www.starlight.demon.co.uk/mooncalc http://www.ummah.org.uk/ildl/mooncalc.html Released: 9th June 1997 ---------------------------------------------------------------------------- "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 Moon Sighting (Global Scan) 3.5.1 Moon sighting criteria used in program 3.6 Option 6. Add/ Delete/ Change/ View Atlas Data 3.6.1. Add data 3.6.2. Delete data 3.6.3. Change data 3.6.4. View data 3.7 Option 7. Change Preferences 3.7.1 Default City 3.7.2 Mode of time entry 3.7.3 Start and End of Summer Time/Daylight Saving Time 3.7.4 Monitor Type 3.7.5 Map Type 3.8 Option 8. Advanced Options 3.8.1 Visibility Criterion 3.8.2 Interval between longitudes 3.8.3 Interval between latitudes 3.8.4 Lower limit of latitude 3.8.5 Upper limit of latitude 3.8.6 Sampling interval to calculate -5 deg sun altitude 3.8.7 Topocentric or Geocentric 3.8.8 Correction for refraction 3.8.9 Apparent or Geometric sunset 3.8.10 Atmospheric temperature 3.8.11 Atmospheric pressure 4. FUTURE DEVELOPMENTS 5. ACKNOWLEDGEMENTS 6. DISCLAIMER 7. GLOSSARY 8. ABBREVIATIONS USED 9. GENERAL MOON INFORMATION 10. CONCLUSION 11. SELECTED REFERENCES ---------------------------------------------------------------------------- 0. COPYRIGHT ---------------------------------------------------------------------------- Moon Calculator (MoonCalc), associated data files and this document are copyright (c) by Dr. Monzur Ahmed 1993-1997. All rights reserved. Data/graphics/maps produced by MoonCalc may be used if accompanied by the following acknowledgement: "data/graphics/map* from MoonCalc 4.0 by Dr. Monzur Ahmed." (*as appropriate) On a Web page an optional link may be made to one 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). No alterations should be made to the program, documentation or data files (apart from the atlas database: DATA.PTC) and the program should be distributed as it's original unmodified ZIP file (moonc40.zip). ---------------------------------------------------------------------------- 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 time and direction of moonrise and moonset, interval between sunset and moonset, interval between sunrise and moonrise, date/time of astronomical new moon (conjunction)and full moon and predicts the likelihood of visualising the young moon from a particular location. MoonCalc provides Hijri calendar data including location dependent Hijri date conversion using predicted lunar visibility. 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 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). 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 about 100 cities already entered). There are many user-configurable features. ---------------------------------------------------------------------------- 2. GETTING STARTED ---------------------------------------------------------------------------- 2.1 Minimum system requirements =============================== The minimum system requirements 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 files should be included on the distribution disk or after unzipping the moonc40.zip archive: MOONC40.EXE The main program DATA.PTC Database of town data, can be modified DEFAULTS.MC Stores initial program default values STARDATA.DAT Data of 9025 stars from Yale Brightstar Database MOONFACE.DAT Data to generate lunar craters WORLDMAP.DAT Data to generate word map README.TXT This file! 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. 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 ============================================= Place your disk in, say, drive A. Now make sure you have the A:> prompt showing: A:> Type MOONC40 <CR> and the program will commence. The floppy should NOT be write-protected as MoonCalc will need to access the disk for temporary storage. 2.5 Installing and running MoonCalc on a hard drive system ========================================================== 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 (IMPORTANT!): cd c:\moon <CR> Now type MOONC40 <CR> and the program will commence. ---------------------------------------------------------------------------- 3. USING THE PROGRAM ---------------------------------------------------------------------------- When the program is run the following MAIN MENU is displayed: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I Moon Calculator Version 4.0 I I By Dr. Monzur Ahmed (c) May 93/June 97 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 Moon Sighting (Global Scan) I I 6. Add/ Delete/ Change Atlas Data I I 7. Change Preferences I I 8. Advanced Options I I X. Exit to DOS I I I I Use cursor keys or 1-8 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 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 3.6). 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 'Option 7. Change Preferences' from the Main Menu; see below). The latitude and longitude should be available from a 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). To see all four screens, 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: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I BIRMINGHAM 52:30N 1:55W TZ:0.0 Height:236m Topo Refrac ON I A I Julian Day Number: 2450103.5 Date: Sun 21 Jan 1996 I I JD of Conjunction: 2450103.0357 Time: 14h 50m 00s LT I I Apparent Sunrise: 8h 01m 31s LT Apparent Sunset: 16h 36m 39s 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: 25.98h 1D 1H 59M I I Phase:0.0194 Width:0.59m Semi-Diam:0.279 Earth-Moon Dist:359942.24km I I--------------------------------------------------------------------------I I Moon Rise: 8h 05m 57s LT Azimuth: 110d 41m 34s I C I Moon Set: 18h 27m 31s LT Azimuth: 252d 06m 58s I I Sunrise-Moonrise: 0h 04m 26s Sunset-Moonset: 1h 50m 51s I I--------------------------------------------------------------------------I I New Moon: 20 Jan 1996 12h 51m 28s TD I D I Full Moon: 5 Jan 1996 20h 52m 01s TD I I--------------------------------------------------------------------------I E I ENT:More [H]elp +/-:▒Mth DEL/INS:▒Day END/HOME:▒Hr DN/UP:▒Min SPACE:Menu I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 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, the date and time as entered and the calculated sunrise and sunset time for that day. '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 sunrise and sunset times for that day are also shown. The user can choose whether to display apparent or geometric sunrise/set - see section 3.8.9. The Julian Day number of the entered date and the Julian date of nearest conjunction are also shown. The top right of the screen will indicate 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). 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, crescent width (Width) in arc minutes, semi-diameter 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. 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 and time of nearest astronomical new moon (conjunction) and full moon. 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. At present TD and GMT (or Universal Time, UT) differ by about 1 minute. 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: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I BIRMINGHAM 52:30N 1:55W TZ:0.0 Height:236m Topo Refrac ON I A I Julian Day Number: 2450103.5 Date: Sun 21 Jan 1996 I I JD of Conjunction: 2450103.0357 Time: 14h 50m 00s LT I I Apparent Sunrise: 8h 01m 31s LT Apparent Sunset: 16h 36m 39s LT I I----------------------------------2 of 4----------------------------------I I AT APPARENT SUNSET> I I New Moon Visibility (Ilyas_C) Should be visible I I Moon Alt: 12.586 12d 35m 11s Moon Azi: 229.757 229d 45m 27s I B I Sun Alt: -0.701 -0d 42m 03s Sun Azi: 238.022 238d 01m 19s I I Rel Alt: 13.287 13d 17m 14s Rel Azi: -8.264 -8d 15m 52s I I Elongation 16.129 16d 07m 43s Moon Age: 27.75h 1D 3H 45M I I Phase:0.0219 Width:0.66m Semi-Diam:0.278 Earth-Moon Dist:360180.68km I I--------------------------------------------------------------------------I I Moon Rise: 8h 05m 57s LT Azimuth: 110d 41m 34s I C I Moon Set: 18h 27m 31s LT Azimuth: 252d 06m 58s I I Sunrise-Moonrise: 0h 04m 26s Sunset-Moonset: 1h 50m 51s I I--------------------------------------------------------------------------I D I New Moon: 20 Jan 1996 12h 51m 28s TD I I Full Moon: 5 Jan 1996 20h 52m 01s TD I I--------------------------------------------------------------------------I E I ENT:More [H]elp +/-:▒Mth DEL/INS:▒Day END/HOME:▒Hr DN/UP:▒Min SPACE:Menu I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 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, 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 one of Ilyas' criterion is being used) to predict if the new moon would be visible from the user's location after sunset on that day. To change the sighting criteria see section 3.8. In the example above, at sunset the relative altitude is 13.29 degrees and the relative azimuth is -8.26 degrees. This satisfies Ilyas' criterion for visibility- hence the program indicates 'Moon should be visible' on 21 Jan 1996 in Birmingham. Enter the above example, go to screen two and press the INSERT key to go back a day to 20 Jan 1996. You will see that on 20 Jan 1996 at sunset in Birmingham the relative altitude is 3.57 degrees and the relative azimuth at sunset is 1.95 degrees. These values do not satisfy Ilyas' 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: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I BIRMINGHAM 52:30N 1:55W TZ:0.0 Height:236m Topo Refrac ON I I Julian Day Number: 2450103.5 Date: Sun 21 Jan 1996 I A I JD of Conjunction: 2450103.0357 Time: 14h 50m 00s LT I I Apparent Sunrise: 8h 01m 31s LT Apparent Sunset: 16h 36m 39s LT I I----------------------------------3 of 4----------------------------------I I WHEN SUN IS ~5░ BELOW HORIZON> Time: 17h 04m 09s LT I I I I Moon Alt: 9.463 9d 27m 47s Moon Azi: 235.559 235d 33m 32s I B I Sun Alt: -5.013 -5d 00m 48s Sun Azi: 243.366 243d 21m 57s I I Rel Alt: 14.476 14d 28m 35s Rel Azi: -7.807 -7d 48m 24s I I Elongation 16.355 16d 21m 18s Moon Age: 28.21h 1D 4H 13M I I Phase:0.0226 Width:0.67m Semi-Diam:0.277 Earth-Moon Dist:360243.69km I I--------------------------------------------------------------------------I I Moon Rise: 8h 05m 57s LT Azimuth: 110d 41m 34s I C I Moon Set: 18h 27m 31s LT Azimuth: 252d 06m 58s I I Sunrise-Moonrise: 0h 04m 26s Sunset-Moonset: 1h 50m 51s I I--------------------------------------------------------------------------I D I New Moon: 20 Jan 1996 12h 51m 28s TD I I Full Moon: 5 Jan 1996 20h 52m 01s TD I I--------------------------------------------------------------------------I E I ENT:More [H]elp +/-:▒Mth DEL/INS:▒Day END/HOME:▒Hr DN/UP:▒Min SPACE:Menu I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Again areas A,C, D and E are unchanged. Area B now shows data for when the sun is about 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, 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 235.6 degrees). The moon will be about 28.2 hours old and will be about 9-10 degrees above the horizon moon altitude 9.46 degrees). 3.1.4 Screen 4 of 4 ------------------- This screen shows Hijri calendar data: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I BIRMINGHAM 52:30N 1:55W TZ:0.0 Height:236m Topo Refrac ON I I Julian Day Number: 2450103.5 Date: Sun 21 Jan 1996 I A I JD of Conjunction: 2450103.0357 Time: 14h 50m 00s LT I I Apparent Sunrise: 8h 01m 31s LT Apparent Sunset: 16h 36m 39s LT I I----------------------------------4 of 4----------------------------------I I HIJRI CALENDAR DATA> 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: 501666 I I Islamic Lunation No: 16989 Astronomical Lunation No: 904 I I Crescent first seen:21 Jan 1996 Criterion: Ilyas_C I I--------------------------------------------------------------------------I I Moon Rise: 8h 05m 57s LT Azimuth: 110d 41m 34s I C I Moon Set: 18h 27m 31s LT Azimuth: 252d 06m 58s I I Sunrise-Moonrise: 0h 04m 26s Sunset-Moonset: 1h 50m 51s I I--------------------------------------------------------------------------I D I New Moon: 20 Jan 1996 12h 51m 28s TD I I Full Moon: 5 Jan 1996 20h 52m 01s TD I I--------------------------------------------------------------------------I E I ENT:More [H]elp +/-:▒Mth DEL/INS:▒Day END/HOME:▒Hr DN/UP:▒Min SPACE:Menu I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 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, the Ilyas_C criterion is being used to calculate Hijri data. However, any of the 12 moonsighting criteria that MoonCalc currently supports may be used (see 3.8.1) 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). 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 *********************************************************************** * The above key combinations 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 3 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 look complicated but after a while you will find the procedure straightforward. Alternatively use screen 4 of 4 which does the above steps automatically! 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 moon's position on it. The positional data for the stars was obtained from the Yale Brightstar Database. The bright limb angle, phase, Right Ascension and Declination of the moon are depicted. 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. The positions of the moon and sun are drawn on this background of stars. The moon is drawn showing the correct phase and orientation taking into account it's bright limb angle and parallactic angle. 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 to 10: 10 Preset zooms (zoom factor 1.1 to 3) D: Set initial default zoom of 1 Cursors: Change direction of view N,E,S,W Change direction of view P: Print screen to Epson/HP compatible printer C: Toggles between clean screen & labelled screen M/m Show more/less stars (i.e. change magnitude) SPACE: Return to main menu Other keys which apply but not shown at the bottom of the screen are: +/- increase/ decrease MONTH DEL/INS increase/ decrease DAY END/HOME increase/ decrease HOUR PAGE DN/UP increase/ decrease MINUTE We can 'see' the moon andd 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 then 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, 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 3.8.7 and 3.8.8). Please note that values of certain physical parameters of the moon given in the 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. Again one can increase/decrease the month, day, hour or minute using 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 appy are: 'C': toggles between 'craters on' and 'craters off'. Switch on the craters feature if you have a fast machine (486DX or higher). With this feature the craters and seas of the near side of the moon are depicted graphically. In a future release, facility for labelling the craters will be provided. '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 based on the work of Danjon (1932, 1936) and Schaefer (1991) 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 Moon Sighting (Global Scan) =============================================== MoonCalc is able to predict the areas of the world where the new 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 initially, fine subsequently). You can scan 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 together with the moon's properties at the time of local sunset. 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) 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 3.8). 3.5.1 Moon sighting criteria used in program -------------------------------------------- "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 AD) Since ancient times, astronomers have tried to predict the likelihood of seeing the new moon by defining minimum visibility criteria. MoonCalc currently supports 12 such criteria. The user can choose the moon visibility criteria to be used (see section 3.8). 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. * Ibn Tariq......................[Alt, Lag] Muslim astronomers extensively investigated the problems of moon sighting especially in the 8th-10th century AD. 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 on the extensive observational data of Schmidt made at Athens over a period of 20 years. 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 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. 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. The Indian criterion was initially developed by Carl Schoch. * Bruin ..........................[Alt, Crescent width] In 1977 F. Bruin published details of a theoretical moon sighting criterion based on crescent width and sun/moon altitude. In it's original form, the criterion was represented by a family of 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 5,6,11 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 relative altitude at sunset versus sun-moon elongation at sunset. If a new moon lies above the curve it 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 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. This is the default criterion used in MoonCalc. * RGO 67........................[Alt, Elong] The Royal Greenwich Observatory produces a series of information sheets which tabulates predicted first moon sightings. 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 an altitude of -5 degrees. The criterion as used in MoonCalc is useful for finding the earliest location where the new moon is likely to be sighted. On a global scan, the criteria 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. 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. * Schaefer 1988.................Not Yet Implemented B.E. Schaefer has developed a complex theoretical sighting criterion based on the idea of Bruin. This criterion takes into account atmospheric haziness, aerosol scattering, Rayleigh scattering, ozone absorption etc (see refs 9,21 and 22). Despite several publications, this criterion has not yet been documented in sufficient detail to implement in MoonCalc. 3.6 Option 6. Add/ Delete/ Change/ View Atlas Data ================================================== The program has a built in database which can store data for upto 1000 cities. The program is shipped with about 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 4.0 I I By Dr. Monzur Ahmed (c) May 93/June 97 I I I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I A T L A S D A T A B A S E I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 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 Use cursor keys or 1-4 to make choice I I I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII It is best to add a town to the atlas before using it so as to save time inputting latitude/longitude data. 3.6.1. 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 7. Change preferences' from the Main Menu, see section 3.7) 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. 3.6.2. Delete data ------------------ Simply type in the name of a location which exists on the database to remove it from the database. Make sure that the spelling is correct (although the case does not matter). 3.6.3. Change data ------------------ Type in the name of a location which already exists on the database and follow the prompts to alter its properties. 3.6.4. View data ---------------- This generates a table showing all the locations stored in the database in alphabetical order. Use Page Up/Down to browse. 3.7 Option 7. Change Preferences ================================ 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 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: 3.7.1 Default City- usually set to the users home town. ------------------- 3.7.2 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 users location. 3.7.3 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. 3.7.4 Monitor Type: Colour or Black & White ------------------- 3.7.5 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. 3.8 Option 8. Advanced Options ============================== 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. The following screen, or one similar to it, will appear when you chose this option: 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 Sampling interval to calculate -5░ sun altitude: 10 secs 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 Pressing 'D' will reset to factory set defaults. To make changes, press the SPACE BAR. 3.8.1 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. Schaefer 1988.................Not Yet Implemented The current choice is 8 Press ENTER to accept or type in new default (0-11): Choose the criterion that you wish (option 8, Ilyas_C is the default used in the program). See section 3.5.1 for further information on each of these criteria. If option 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 7). 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 criteria 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). 3.8.2 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. 3.8.3 Interval between latitudes -------------------------------- This option defines the interval between successive latitudes during the first scan of the globe. The same comments as for 3.8.2 apply. 3.8.4 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. 3.8.5 Upper limit of latitude ----------------------------- See section 3.8.4. Range allowed for upper limit 30-90 degrees; default 60 degrees. 3.8.6 Sampling interval to calculate -5 deg sun altitude -------------------------------------------------------- In screen 2 of option 1, MoonCalc gives data relating to when the sun is 5 degrees below the horizon (see section 3.1). This time is calculated by initially calculating the time of local sunset and then successively adding a fixed interval to this time and sampling the calculated altitude of the sun (until the altitude is -5 degrees). If the sampling interval is set to a small value it will take longer to calculate the time when the sun is -5 degrees below the horizon. Range allowed 1-60 seconds, default 10 seconds. 3.8.7 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. 3.8.8 Correction for refraction ------------------------------- Choose "Yes" if you want to compensate for atmospheric refraction. 3.8.9 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' and Topocentric/Geocentric to 'Geocentric'... then: -relative altitude at sunset = ARCV -relative azimuth at sunset = DAZ -elongation at sunset = ARCL 3.8.10 Atmospheric Temperature ------------------------------ The value will effect the internal calculation of refraction. Usually this should be set in the range 10-25 degrees Celsius. 3.8.11 Atmospheric Pressure --------------------------- The value will effect the internal calculation of refraction. Usually this should be set to 1010 millibars. ---------------------------------------------------------------------------- 4. FUTURE DEVELOPMENTS ---------------------------------------------------------------------------- This is the first 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 including addition of a report generator, automatic monthly lunar calendar generator, a more advanced help system and mouse support. I am currently 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 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 3-4 years. In particular, I should like to thank Shakoor Chughtai for his helpful comments and extensive error testing. Thanks are due to Tariq Muneer for introducing me to the subject of moon sighting and suggesting that I should write this program. I am indebted to Omar Afzal for providing me with certain (difficult to locate) reference materials. I am grateful to the many, many people who made useful comments on the earlier beta releases of MoonCalc including Rashid Motala, Yusuf Essack, Yaacov Loewinger, Geoff Hitchcox, Robert H. van Gent and Mohammad Ilyas. 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 daughter Zahra who was 10 weeks old when MoonCalc version 4.0 was released. She didn't actually help with version 4.0 but come version 5 or 6..... :-) ----------------------------------------------------------------------------- 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. * 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 ---------------------------------------------------------------------------- Azi Azimuth Alt Altitude BLA Bright Limb Angle DST Daylight Saving Time Dec Declination Elong Elongation Geo Geocentric GMT Greenwich Mean Time hr(s) Hour(s) LT Local Civil Time 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. CONCLUSIONS ---------------------------------------------------------------------------- MoonCalc was developed over a period of 4 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), MBChB, MRCP(UK). 27 Poplar Road, Birmingham, B11 1UH, UK. email: monz@starlight.demon.co.uk http://www.starlight.demon.co.uk/mooncalc http://www.ummah.org.uk/ildl/mooncalc.html 9th June 1997 ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- 11. SELECTED REFERENCES ---------------------------------------------------------------------------- 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. 5. Mohammad Ilyas; A Modern Guide to Astronomical Calculations of Islamic Calendar, Times & Qibla,1984;Berita Publishing Sdn Bhd.; Kuala Lumpur, Malaysia 6. 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. 7. Schaefer B.E., Ahmad I.A. and Doggett L.; Records for Moon Sightings; Q.J. Ast. Soc. (1993), 34:53-56 8. 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. 9. Schaefer B.E., Visibility of lunar crescent; Q.J R. Ast. Soc. (1988), 29:511-523 10. Caldwell J. and Laney D. Young Crescent Visibility Predictions for 1997 (Islamic 1417/1418); South African Astronomical Observatory. 11. Ilyas M. Lunar Crescent Visibility and Islamic Calendar; Q.J.R. Ast. Soc. (1994), 35:425-461. 12. The Star Almanac for Land Surveyors, London, HMSO. 13. Explanatory Supplement to the Astronomical Ephemeris, London. 14. Fotheringham J.K. On the smallest visible phase of the moon; Mon. Not.R. Astron. Soc. (1910),70:527-531. 15. Maunder W. On the smallest visible phase of the moon; J. British Astron Assoc (1911),21:355-62. 16. Indian Astronomical Ephemeris, 1979, India Meteorology Department, New Delhi. 17. Bruin F. The first visibility of the lunar crescent. Vistas Astron (1977):21:331-358 18. Ilyas M. Limiting altitude separation in the Moon's first visibility criterion. Astron Astrophys (1988),206:133-135. 19. Schaefer B.E., Length of the Lunar Crescent;Q.J.R. Astron. Soc.(1991), 32:265-277 20. Eckhardt E.K. Theory of the libration of the moon. 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