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Program ASTROCLK

Astronomical Clock and Celestial Tracking Program

with Celestial Navigation

by David H. Ransom, Jr.Rancho Palos Verdes, CA

Version 8947November 19, 1989

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ASTROCLK Astronomical Clock and Celestial Tracking Program Page i

TABLE OF CONTENTS

ACKNOWLEDGEMENTS.........................................1INTRODUCTION.............................................2HARDWARE REQUIREMENTS....................................7PROGRAM OPERATION........................................10

Required ASTROCLK Files...............................10Starting Program ASTROCLK.............................12Running Program ASTROCLK..............................13

FUNCTION KEYS AND HELP...................................18F1 Display HELP Screens...............................18F2 Display Target Object EPHEMERIS....................18F3 Set Time and/or Date...............................18

Read Hardware Clock................................19Set ALARM or INTERVAL TIMER Time...................19

F4 Toggle Clocks ON or OFF............................19Enable Simulated Real Time.........................19

F5 Set Target Coordinates.............................20Enter USNO Star Name or Number.....................20Search for Nearest USNO Star.......................20Search EXTERNAL STAR CATALOG by Name or ID.........20Search EXTERNAL STAR CATALOG by RA and DEC.........21Search EXTERNAL STAR CATALOG for Nearest Star......21Manual Target Data Entry...........................21Set Polaris Coordinates............................22

F6 Set Local Coordinates..............................23Set Destination Coordinates........................23Set Local Conditions...............................23

F7 Set Display Format.................................23Change Target Display Coordinates..................24

F8 Precess Internal Star Database.....................24F9 DOS Shell..........................................25

Execute Preset DOS Command.........................25Execute USNO Ephemeris (ICE or FA).................25

F10 Celestial Navigation...............................26Setting Program Options............................26

0-9 Select Display Window Mode.........................26SETTING PROGRAM OPTIONS..................................28Setting the DAYLIGHT FLAG.............................28Setting the ZONE CORRECTION...........................29Setting the COLOR FLAG................................29Setting the ICE/FA FLAG...............................30Setting the CALENDAR FLAG.............................30Setting the FILE NAMES and PATHS......................31Setting the PRESET DOS COMMAND........................33

SETTING LOCAL/UT/TDT TIME AND DATE.......................34Setting the LOCAL/UT/TDT Time.........................36

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ASTROCLK Astronomical Clock and Celestial Tracking Program Page 1

ACKNOWLEDGEMENTS

Few tasks of any consequence are accomplished unaided. ForASTROCLK, in addition to the numerous references cited in theBIBLIOGRAPHY, there are several individuals to whom specialthanks are due.

Ward Harman, a retired engineer living near me in PalosVerdes, California, has spent many hours testing and validatingthe performance of various aspects of ASTROCLK, advising me oferrors when he found them, and making numerous suggestions withrespect to both style and substance.

Steve Brewster, of Stony Ridge Observatory high abovePasadena, California, has been most generous with his time,advice, and encouragement. To all of that, he added a long andfascinating evening at the Observatory where we were able toexperience firsthand the thrill of "real" astronomy using SRO's30-inch reflector and which helped me to better understand howASTROCLK might be used in that environment.

And to all of those interested astronomy and computerenthusiasts who have called, written, or left messages for me onmy bulletin board system, my thanks for your kind words andsuggestions. Those letters and calls inform me that ASTROCLK isbeing used in Europe, Hong Kong, Japan, Israel, and Australia inaddition to the United States and Canada. I must be doingsomething right! ASTROCLK is now embarking upon its third year.

Finally, and by no means least, my wife Vicki has been bothpatient and supportive during the many hundreds of hours I havespent hunched over one or another of my computers as ASTROCLK hasevolved from a simple sidereal clock to the complex program it istoday. It was her interest in, and curiousity about, astronomyand the night sky which helped inspire my efforts in the firstplace, and her encouragement has been essential during the yearsthat I have invested in ASTROCLK.

November, 1989

David H. Ransom, Jr.Rancho Palos Verdes, CA

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INTRODUCTION

Program ASTROCLK is an Astronomical Clock and CelestialTracking Program. ASTROCLK is free for non-commercial use. Use itif you like it, discard it if you don't. There are no warrantiesof any kind. If you wish to use ASTROCLK commercially, write forlicense information. For information on how to obtain the mostrecent version of the program, see the section A BRIEF EDITORIAL.And now, on with the story ...

Like many people, I have long been fascinated by the starsat night and by things astronomical. But it was not until someyears ago, when I spent considerable time in the foothills ofNorthern California, that I regularly saw the night sky withoutthe interference of city lights. There followed a heightenedinterest in the stars and a desire to be able to recognize thevarious constellations and important individual stars. Manybooks, star charts, and cold winter nights later the age of thePersonal Computer dawned. Suddenly, I realized, I had a toolwhich would enable me to figure out many of these things on myown and practically in real time.

Program ASTROCLK has evolved from a series of smallerprograms, each designed to calculate some little piece ofastronomical data which I needed or wanted for use with my hobby.Each time that I needed still another bit of data in order to dosomething, I'd search out the necessary formulae or methods andwrite a new little program to automate the process. After arelatively short period of time I discovered that I had literallydozens of such small programs, but no single program was eversufficient to get me all the information I sought at a particulartime.

Equally frustrating, none of the stand-alone programsavailable or that I had written up to that point gave me theinformation in real time, adjusted for my geographical location.I always had to look up all the things I'd forgotten or runa number of programs to get the data I sought. And to furthercomplicate things, there are an almost unbelievable number ofdifferent methods for telling time, of which perhaps half a dozenor so are useful to the casual astronomer or navigator. I finallymastered the zone changes from Greenwich to Los Angeles, butconverting local time to sidereal time ("star time", if youprefer) in my head has so far eluded me. Program ASTROCLK wasintended to solve all of these problems for me. While it is stillsome distance from accomplishing that rather ambitious goal, it's

a very big step along the way. I'm starting to run out of"necessary" features to add!As with any profession, astronomers and navigators have

developed a technical language all their own to describe thephenomenae of time and celestial mechanics. Not only is thislanguage almost as complex as the science it seeks to describe,but many seemingly common words carry definitions far divorcedfrom everyday life and our intuitive understanding of theirmeaning. The amateur astronomer or layman can easily becomehopelessly confused, particularly as not all texts,organizations, and related professions necessarily use precisely

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the same words or even the same definitions to describe a givenmeasurement or item of data. All too frequently the definitionshave changed over time, and sometimes they are even reversed fromone discipline to another.

For my own understanding and entertainment, I have spentconsiderable time researching the subject and attempting toassemble a consistent set of computer programs and algorithms tofacilitate the practical use of my personal computers inastronomy and navigation. Program ASTROCLK now represents acontinuing effort spanning almost two years and more than athousand hours of work. I hope that effort is judged worthwhile.

The advent of the truly portable personal computer hasserved as an additional spur to these efforts so that I may havethe information at my fingertips no matter where I may travel.There are moments when I wonder who is the slave and who theservant.

I have used many and varied sources and have made everyeffort to assure the accuracy of the information and calculationspresented. However, I alone am responsible for the final outcome-- along with any errors that may be discovered. My thanks tothose individuals who have taken the time to report problems andsuggest improvements. Without their interest and encouragement, Idoubt that ASTROCLK would have become what it is or that myefforts would have continued.

The first and most important order of business for anyastronomer or navigator is to know what time it is. For ASTROCLK,I assume that the computer's internal clock has been set to thecorrect local time, keeps reasonably good time, and that therelationship between local time and Coordinated Universal Timecan be calculated or is known. To a high degree of accuracy,what is now known as Coordinated Universal Time (UTC) waspreviously called Greenwich Mean Time; there are those who stillinsist on using the old name. The U. S. military forces, everadept at finding a different name for things we might otherwiserecognize, refer to UTC as Zulu Time. In the United States, theNational Bureau of Standards continuously broadcasts UTC onstations WWV (Fort Collins, Colorado) and WWVH (Kauai, Hawaii);the frequencies transmitted are: 2.5MHz, 5MHz, 10MHz, 15MHz and20MHz (WWV only). Reception will vary depending upon the time ofday, geographic location, and current atmospheric conditions. InEurope and in many places around the world, the BBC World Servicegives a time signal every hour which is synchronized withGreenwich Mean Time, essentially identical with UTC.

As an aside, I have noticed that the hardware clocks in my

computers maintain more accurate time than do the software clocks(particularly with versions of MS-DOS prior to 3.xx). Further,some programs which use high speed serial communications disablethe software clock during operation and the time errors canbecome substantial. Other software can also suspend timekeepingfunctions for brief intervals. On my Zenith Z-248 system (an IBMAT-compatible), for example, use of the program BROOKLYN BRIDGE(inter-computer communications) can introduce errors of tens ofseconds or more. I recommend that you first check the accuracy ofyour software clock, the one that keeps track of time after youbegin using the computer, over a period of several hours. An easy

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way to do this is simply to run ASTROCLK and observe thedisplayed local time compared to an accurate clock or watch.Second, if you temporarily leave ASTROCLK using Function Key F9,note the time when you return to ASTROCLK and, if the time is inerror, make a note of what programs or operations in your systemaffect the accuracy of the software clock. In either case, resetyour software clock from time to time if necessary or, if yourcomputer has a hardware clock, re-read your hardware clock totake advantage of its superior accuracy. For many computers,ASTROCLK can do this using Function Key ALT-F3.

Using this more or less accurate time standard, ASTROCLKdisplays the current Local Time and Local Date, the Local MeanSidereal Time ("star time"), and the Local Mean Solar Time(referred to the local longitude). Also shown are: CoordinatedUniversal Time (UTC) which, for years 1925 and later and to theaccuracy used here, is the same as Greenwich Mean Time (GMT); theUTC Date at the Prime Meridian (Greenwich, longitude 0 degrees);Greenwich Mean Sidereal Time; and, the local time zone relativeto UTC. All times are in 24-hour notation and local time is LocalStandard Time or Local Daylight Time, depending upon the settingof the DAYLIGHT FLAG. If your time zone is offset from thecomputed local time zone, see also the section SETTING PROGRAMOPTIONS. Note that dates are shown as DD-MM-YYYY (European style,day-month-year) and that because of the time span covered thefull 4-digit year is required. Any one of the times may bedisplayed in a main window with extra large digits for easyvisibility.

Precision Time and Data Displays are available which show avariety of common time standards to a precision of 0.0001 secondsalong with other astronomical information. The display is updatedeach second -- provided the computer can make the necessarycalculations in that time. If the clocks are stopped, the usermay enter any desired time and date and view the calculatedvalues for all of these items to a high degree of accuracy. Thevalues have been carefully checked against the AstronomicalAlmanac, prepared each year jointly by the U. S. NavalObservatory (USNO) and the Royal Greenwich Observatory, and theUSNO Floppy Almanac and are believed accurate to within plus orminus 0.01 seconds or better; note that the displayed precisionis 0.0001 seconds.

Initially, the program assumes the geographical location ofRancho Palos Verdes, California, near Los Angeles. However, anauxiliary file contains the names and locations of a number ofAmerican and Canadian cities which can quickly be read by

ASTROCLK. The file may easily be edited to include your favoritelocations and their coordinates. If you change the localcoordinates, ASTROCLK saves them in a special file, ASTROCLK.INI,and the new place name and coordinates will be automaticallyloaded when the program is next started.

A tracking feature is included which allows the user tocontinuously display the celestial and horizon (observer)coordinates for the pole star, Polaris, and the 57 starsdesignated by the U. S. Naval Observatory (USNO) as "StandardNavigational Stars". Data for these stars are preset in theprogram and are for Epoch J2000.0, the current standard epoch for

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B.C. until October 4, 1582 after which the Gregorian Calendar isused. This follows civil usage in catholic countries as well asastronomical convention, but will not correspond to the dateconvention used in countries which did not adopt the GregorianCalendar in October of 1582. Great Britain and its colonies(including what is now the United States), for example, did notadopt the Gregorian Calendar until September 2, 1752. Dates priorto the introduction of the Julian Calendar in 46 A.D. are inaccordance with the Julian Proleptic Calendar (the JulianCalendar extended backwards in time from 46 A.D.) and aretherefore more or less a figment of the program's imagination;the dates computed are consistent with that calendar (andastronomical convention) but bear no relation to any calendar inactual use at the time. A program option is available to choosebetween the strict Julian calendar and either the 1582 or the1752 adoption of the Gregorian calendar. An additional datedisplay is also available which shows several styles of JulianDate, the local date, the current day of the year, and the day ofthe week.

ASTROCLK is presently being used at several observatoriesfor both time and tracking displays. Beginning with Version 8903,the display may be set to the RED mode so that all displays arepresented in red; the monitor intensity may then be adjusted forbest comfort and protection of night vision. A GREEN mode is alsoavailable which may reduce eye fatigue during periods of extendeduse.

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HARDWARE REQUIREMENTS

ASTROCLK was designed for and is best operated using a coloradapter and color monitor, CGA/EGA/VGA. The program can be forcedto emulate monochrome output on color video adapters with the"/M" command line option. Limited tests on a monochrome system(true monochrome adapter and display, as opposed to a systemusing a monochrome display on a color-compatible adapter), havebeen successful when used with the "/M" command line option. Theprogram has so far been tested on the following systems:

ALR 20386DT ComputerVGA Video Graphics Adapter (Paradise VGA Plus)VGA High Resolution Color Display (Zenith ZCM-1490)80387 math coprocessor

Zenith Z-386 ComputerVGA Video Graphics Adapter (Zenith Z-449)VGA High Resolution Color Display (Zenith ZCM-1490)80287 math coprocessor

Zenith Z-248 (IBM PC-AT compatible)VGA Video Graphics Adapter (Paradise VGA Professional)VGA High Resolution Color Display (Zenith ZCM-1490)80287 math coprocessor

Zenith Z-248 (IBM PC-AT compatible)EGA Enhanced Graphics Adapter (Quadram QuadEGA and

Zenith Z-449)ECD Enhanced Color Display (Princeton HX-12E)80287 math coprocessor

Zenith Z-248 (IBM PC-AT compatible)VGA Video Graphics Aray (Paradise VGA Professional)Monochrome Display (Zenith ZVM-1240)No math coprocessor

Zenith Z-181 and Z-183 Laptop ComputersInternal CGA Color Graphics AdapterInternal Twisted-Crystal DisplayNo math coprocessor

Zenith Z-151 (IBM PC-XT compatible)

Standard CGA/Composite Color Graphics AdapterMonochrome Monitor (Zenith ZVM-1230A)Color Monitor (Mitsubishi CS-2061R)8087 math coprocessor

Zenith Z-148 (IBM PC-XT compatible)Internal CGA Color Graphics AdapterRGBI Color MonitorNo math coprocessor

Several users have also reported successful operation on

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other systems including an IBM PS/2 Model 80 and a Compaq Model386/20. The program has also been tested on various "IBM-clone"systems with numerous variations including CGA/EGA/VGA GraphicsAdapters and Hercules Graphics Adapters (HGC). The only problemencountered was with a 101-key keyboard emulator (supplied byMicrosoft!) which caused the system to hang when ASTROCLK wasexecuted; a reboot was required to resume operation. When theemulator program was removed, ASTROCLK executed withoutdifficulty.

Several ASTROCLK functions use the QuickBASIC SHELL commandto execute DOS commands directly or to return the user to asecondary command processor (Function Key F9). All of my systemsuse MS-DOS Version 3.1 or higher but I have read reports thatthe QuickBASIC SHELL does not operate correctly for versions ofMS-DOS or PC-DOS of 3.0 or lower. I recommend that you upgrade toVersion 3.2 or higher for better system performance in generaland to avoid problems with the SHELL command in particular.

ASTROCLK supports the EGA 43-line mode to a limited extent:if the system is in that mode at program startup, it will returnto that mode upon final exit. I'm rather fond of the EGA's 35-line mode and often use it in preference to either 25- or 43-linemodes. Unfortunately for me, QuickBASIC (any version) refuses torecognize the 35-line mode on entry and returns the system to the25-line mode upon exit. Regardless of the screen mode detected atthe start of execution, ASTROCLK always sets the system to 80columns and 25 lines for maximum compatibility and ease ofviewing.

The "/M" command line option (see PROGRAM OPERATION, below)is recommended for systems equipped with a monochrome displayadapter and monochrome monitor. It also forces monochrome displayon computers which have CGA-compatible video adapters butsimulate colors with shades of gray or varying intensities of asingle color, such as the Zenith Z-181 and Z-183; these computersotherwise require some adjusting to see the shades of blue,especially bright white on green background (used for LOCALCOORDINATES and HELP screens). The green monochrome monitor on myZ-151, on the other hand, rendered all colors visible. Resultswill obviously vary from system to system. Limited tests havebeen performed on systems equipped with a monochrome videoadapter using the "/M" command line option and the programperformed properly.

The performance of different computers varies considerably,the single most important factor being the presence or absence ofa math coprocessor. Program ASTROCLK uses the double precision

floating point format for almost all significant calculations,and the added performance of the coprocessor is significant.Without it, even an AT-class computer has perceptible delays inthe Precision Time and Data Displays; with it, an old PC-classcomputer easily completes the same tasks within one second. Tomeasure the performance under these conditions, a special versionof program ASTROCLK was prepared to time the nutation andobliquity of the ecliptic calculations required for thecomputation of Apparent Sidereal Time. The following table showsthe results of the tests on several different computerconfigurations ranging from a PC/AT-compatible to my oldest

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machine, a PC/XT-compatible. For comparison, the Norton UtilitiesSystem Information Computing Index (SI) is shown. Computationtime only is measured for a single iteration of the calculations(8825) and for the average of ten interations (8826A). Unlessotherwise noted: the compiled version of ASTROCLK was used; allcomputers were running MS-DOS Version 3.1 or higher; all computermodels are Zenith part numbers; and, all times are in seconds andare typical except clock speed is in MHz. The math coprocessor isnot the only factor in execution speed; significant softwareimprovements were made in Version 8826A as compared to Version8825. The times for both versions are shown for comparison. (Notall system configurations were available for testing Version8826A.)

CPU/COPROCESSOR PERFORMANCE COMPARISONS---------------------------------------

8825 8826AMODEL CLOCK CPU COPRO TIME TIME** SI---------------------------------------------------------Z-386 16.00 80386 ----- 0.88 0.07Z-248 8.00 80286 80287 0.38* 9.0Z-248 8.00 80286 80287 0.27 0.015 9.0Z-248 8.00 80286 ----- 1.65 9.0Z-183 4.77 80C88 ----- 9.35 0.87 1.0Z-183 8.00 80C88 ----- 6.59 0.60 1.6Z-151 4.77 V-20 8087 0.60 0.03 1.8Z-148 4.77 8088 ----- 9.35 0.85 1.0Z-148 8.00 8088 ----- 5.48 0.51 1.7

* QuickBASIC interpretive mode** Average of 10 iterations of calculations

All machines performed "normal" calculations without unduedelay. The various clock displays were updated every second andonly in the Target Tracking Display, Precision Time and DataDisplays, and the Planetary Data Displays (modes 0, 8 and 9) werecomputational times very noticeable; slower machines, especiallyany machine without a math coprocessor, required from 2 to 5seconds to update the calculations depending upon the mode.Planetary position calculations, being the most complex, requirethe most computational time and involve the greatest delays.

I have not tested the minimum memory requirements forASTROCLK. All of my systems are equipped with 640K. As of Version

8907, the program requires more than 200K bytes of memory andprobably WILL NOT execute in a minimum 256K system. SinceASTROCLK can invoke QuickBASIC's SHELL command to return youtemporarily to DOS with ASTROCLK still in memory, I recommend theuse of 640K memory. However, even with 640K of memory, the factthat ASTROCLK is resident means that programs which require agreat deal of memory may fail to execute properly under theshell. These programs must be executed outside ASTROCLK.

Comments and test results from other system configurationsare welcome. Note that future versions of ASTROCLK may requireadditional memory and/or disk space.

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PROGRAM OPERATION

This section describes the operation of program ASTROCLK,including required files, starting the program, and initialoperations.

Required ASTROCLK Files

Program ASTROCLK is normally distributed in archived formand includes the following files:

ASTROCLK.EXE Executable ASTROCLK programASTROHLP.EXE Executable ASTROHLP program

ASTROCLK.BAS Main ASTROCLK source for QB4ASTROCLK.CAT Data file of additional starsASTROCLK.CTY Data file of cities/locationsASTROCLK.DC1 ASTROCLK Documentation, Part IASTROCLK.DC2 ASTROCLK Documentation, Part IIASTROCLK.HST Revision history for ASTROCLKASTROCLK.INI * Data file for initializationASTROCLK.MAK Source module list for QB4ASTROCLK.MPC Minor Planet CatalogASTROCLK.PIF PIF file for Microsoft WINDOWSASTROFNT.COM EGA Soft Font (EXPERIMENTAL)ASTROHLP.BAS Program source for ASTROHLP, QB4ASTROSB1.BAS SUB/PROCEDURE source for QB4, 1/3ASTROSB2.BAS SUB/PROCEDURE source for QB4, 2/3ASTROSB3.BAS SUB/PROCEDURE source for QB4, 3/3MESSIER.CAT Data file of Messier objects onlyREAD.ME * Latest information/changesUSCITIES.CTY 718 U. S. city coordinates

* May not be present in archived files

Program ASTROCLK if often distributed via bulletin boardsystems and on disk as three compressed files. A complete versionshould contain ALL of the listed files except as noted. Dependingupon the source, different file compression programs may berequired to unpack the files; the required program is usuallyindicated by the filetype of the archived files.

Only the files ASTROCLK.EXE and ASTROHLP.EXE are required

for operation of the program. If necessary, file ASTROHLP.EXE maybe omitted but the on-screen help functions will not operate andno warning message will be given.

File ASTROCLK.CTY adds the capability to read the locationof various U. S. and Canadian cities; a warning message isdisplayed if it is not present and a search of the file isattempted. File ASTROCLK.CAT contains data for 1645 stars andgalaxies which may be requested by name or number; a warningmessage is displayed if the file is not present and a catalogsearch is requested. File ASTROCLK.INI is not normally included;it is quite small and will be created automatically. File

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ASTROCLK.PIF allows the program to be run under Microsoft WINDOWSif sufficient memory is available; it has been tested withVersion 2.03. File READ.ME contains recent information or changesnot described in this file and may or may not be included.

An additional catalog file, MESSIER.CAT, contains data forthe 109 Messier objects which has been extracted from fileASTROCLK.CAT, for convenience in locating these objects. Anadditional city file, USCITIES.CTY contains coordinates for 718U. S. cities to higher accuracy than file ASTROCLK.CTY.

Beginning with Version 8908, ASTROCLK can also process andtrack minor planets, comets, and asteroids. File ASTROCLK.MPC isan external binary catalog containing the first 250 minor planetswhich may be selected by Minor Planet Number or Name. The binarycatalog has been prepared with my program MPCAT, developed forthis purpose, using data compiled by E. G. Bowell of the LowellObservatory and provided by Ed Tedesco of the Jet PropulsionLaboratory. The full minor planet catalog, EPHEM891.MPC with3,774 minor planets, comets, and asteroids, is availableseparately from my bulletin board system. New updated minorplanet catalogs are released at approximately six monthintervals. These versions of the minor planet data have beenconverted into the binary format expected by ASTROCLK usingprogram MPCAT; as with program ASTROCLK, the current version ofMPCAT and the source are always available from my bulletin boardsystem (BBS). See the section A BRIEF EDITORIAL for moreinformation on the BBS.

As an experiment for EGA users, file ASTROFNT.COM providesan alternate screen font. The screen typeface is changed from itsnormal appearance to a cleaner typeface resembling Helvetica. Touse this screen font, enter "ASTROFNT" prior to executing programASTROCLK (the cursor may disappear but don't worry!) or press theletter "E" during normal operation. CAUTION: Use of ASTROFNT withother display adapters may produce unpredictable results!

ASTROCLK is written and compiled using Microsoft QuickBASIC,Version 4.50. Source files ASTROCLK.BAS, ASTROSB1.BAS,ASTROSB2.BAS, and ASTROSB3.BAS are all required for use with thecompiler. In addition, ASTROCLK.MAK is required for use in theinterpreter mode. Although I normally compile and link fromwithin QuickBASIC, the following batch file may be used tocompile and link ASTROCLK to produce a stand-alone .EXE file (allfiles assumed in the current drive and directory):

bc astroclk/e/x/o/t/c:512;bc astrosb1/o/t/c:512;

bc astrosb2/o/t/c:512;bc astrosb3/o/t/c:512;link /ex astroclk+astrosb1+astrosb2+astrosb3,astroclk.exe;

Note that the compile and link commands may be particular to theversions of BC and LINK being used, Version 4.50 and Version 3.69respectively in this case. See A BRIEF EDITORIAL near the end ofthis document for information on how to obtain the most recentversion of all ASTROCLK files.

Users who require minimum size run files because of memoryconstraints may choose to compile and link ASTROCLK to use

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Microsoft's runtime module, BRUN45.EXE, instead of generating astandalone program. Approximately 40K less RAM memory is requiredfor ASTROCLK in this configuration. However, this configurationis less flexible with respect to starting directory: BRUN45.EXEmust be in the same directory as ASTROCLK.EXE, and ASTROCLK mustbe run from that directory. Batch files which work correctly withthe standalone version may have to be modified.

Beginning with Version 8933, the help functions for ASTROCLKwere removed to a separate program, ASTROHLP.EXE, automaticallyexecuted by Function Key F1. The source file for help isASTROHLP.BAS. This change reduced the size of the main ASTROCLKprogram by 10K bytes and reduced the RAM memory requirements byabout the same amount, but subsequent versions have more thanused up the memory again.

Starting Program ASTROCLK

To start ASTROCLK, first verify that your computer is set tothe correct local time and date using the TIME and DATE commands,then enter one of the following commands at the DOS prompt:

ASTROCLK [for all COLOR monitors]

ASTROCLK /M [for MONOCHROME monitors]

ASTROCLK /R [to force RED on color monitors]

ASTROCLK /G [to force GREEN on color monitors]

followed by RETURN (or ENTER, which I will call RETURN) and theprogram will begin execution. The descriptions and examples inthis documentation assume you are using a color monitor; if youare using a monochrome monitor, ignore all references to colors.However, all users should note that negative years, described asRED in this documentation, will BLINK in the program's datewindows when the "/M" option is used or when either of the singlecolor program modes is set; the UTC Julian Date window, ofcourse, will show the correct number for all dates.

Using one of the command line color options forces theprogram to that color mode immediately and overrides any priorcolor mode. When a color option is NOT used, ASTROCLK willinitially display its signon screen in full color (for colormonitors); using the "/R" or "/G" color option will use the

selected color for the signon screen as well as all subsequentoperations. This is particularly useful with the RED option toprotect night vision when alternating between ASTROCLK and otherprograms. ASTROCLK may also be switched between the monochrome,color, red, and green modes during execution using Function KeyALT-F10. See the section SETTING PROGRAM OPTIONS for furtherinformation.

As initially configured, ASTROCLK assumes that the all datafiles are in the current drive and directory. If this is not thecase, you may include the drive and path for the various ASTROCLKdata files using the following command pattern (note space after

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ASTROCLK):

ASTROCLK [drive:][\path][coloroption]

"drive:" must be a single letter followed by a colon and mustcorrespond to a valid drive. If no path is included, ASTROCLKassumes the current directory on the specified drive or, if nodrive is included, on the current drive. If the path is included,it must begin with the backslash, "\", and the path must exist.See your DOS manual for an explanation of paths and directories.

If present, the color option must follow the drive and/orpath; only ONE of the color options /M, /R, or /G may be used toforce MONOCHROME, RED or GREEN respectively. Using a color optionwill override any prior color setting saved in file ASTROCLK.INI.If no color option is included on the command line, ASTROCLK willstart in full color, then read the file ASTROCLK.INI (if present)and set the color to the mode last used.

For example, if all data files are on disk drive B: insubdirectory ASTROCLK and you want to force monochrome display,the following command should be used:

ASTROCLK B:\ASTROCLK/M

********************* IMPORTANT NOTE *********************

Once ASTROCLK has been executed the first time, the driveand path information are saved in the program initializationfile ASTROCLK.INI. Thereafter, ASTROCLK uses the informationin ASTROCLK.INI and overrides any drive or path specificationentered on the command line. However, the command line coloroptions (/M, /R, or /G), if present, will take precedence overthe previous color saved in the file. Use Function Key ALT-F10 tochange the drive and/or subdirectory from within ASTROCLK, ordelete file ASTROCLK.INI at the DOS prompt to start over. See thesection SETTING PROGRAM OPTIONS for additional information.

* * * * *

Running Program ASTROCLK

When ASTROCLK begins, a title screen will appear and the

program will perform various initialization tasks. After a fewseconds ASTROCLK will display the Local Standard Time (orDaylight Time if it has previously been set using the DAYLIGHTFLAG entry with Function Key ALT-F10) in the main display windowand all clocks will be running. For time zones in the UnitedStates, the correct zone name will be displayed.

The program reads your DOS software clock for the currenttime and date; set your system clock accurately before you runASTROCLK using your hardware clock if your computer has one orusing the TIME and DATE commands if not. If your version ofMS-DOS includes the program RTCLOCK (supplied with Zenith 80286,

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80386, and laptop computers), you may use ALT-F3 to set thesystem clock from the internal hardware clock. If the program toread your hardware clock has a different name, create a batchfile named RTCLOCK.BAT which includes the required command(s),make sure it can be located via the PATH command, and then youmay use ALT-F3 to update the software clock.

For example, my Zenith Z-151 includes a special (non-Zenith)hardware clock which requires a program called RDCLOCK to set thesoftware clock from the hardware clock. I reset the softwareclock using the following command in a batch file calledRTCLOCK.BAT:

RDCLOCK >NUL

This reads the hardware clock, sets the software clock, and sendsits screen output to the "bit bucket" (throws it away to aspecial DOS device called "NUL") so that it does not disturb myASTROCLK display.

I have also noticed that for some systems the software clockis not set properly when the system boots but is slow by somefive or ten seconds. This may be a peculiarity of the Zenith MS-DOS 3.2x software being used on the system in question, butapparently the computer reads the hardware clock at some pointduring the boot process, then does something which suspends theclock before it turns the system over to me. I have solved theproblem by inserting the RTCLOCK command near the end of myAUTOEXEC.BAT file. Now the software clock is set again after allof the odds and ends have been gotten out of the way.

If you do not have a program which reads your hardware clock,or if you do not have a hardware clock, you can exit temporarilyback to DOS using Function Key F9 to set or reset the time and/ordate with the DOS TIME and DATE commands. Then enter EXIT toreturn to ASTROCLK.

It is also possible to "fool" ASTROCLK by setting the DOSsystem clock to any desired date and time. However, because of aninternal DOS software limitation, the DOS clock may only be setfor years from 1980 through 2199; in general, I recommend thatyou use ASTROCLK's SIMULATION mode of operation for non-currentdates.

************** CAUTION **************

Beginning with DOS Version 3.3, the DOS DATE and TIMEcommands may set BOTH the software AND the hardwareclocks for most AT-class and 386-class computers aswell as some others. Therefore, do NOT use the DOS DATEand TIME commands with DOS Version 3.3 and higher ifyou wish to preserve the setting of the hardware clock.

The program automatically presets the celestial coordinatesfor the star POLARIS (Alpha Ursae Minoris), the first andbrightest star of the constellation Ursa Minor (Little Bear).POLARIS is commonly referred to as the pole star because of its

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close proximity to the celestial (and geographical) North Pole.As a result, it has long been used for navigation and thealignment of astronomical instruments. More recently, it is oftenused to align satellite dishes.

Since I don't know where you live, the program starts outwith the geographical coordinates for Rancho Palos Verdes,California, near Los Angeles. These coordinates are displayed inthe lower left portion of the screen. However, in order to usethe sidereal time and celestial tracking features for your ownlocation, you need to know your local longitude (West isnegative) and latitude (South is negative).

Goode's World Atlas, 17th Edition, (see BIBLIOGRAPHY) is anideal reference for this purpose; the Index contains some 30,000cities and other locations worldwide along with theirgeographical coordinates to a precision of one minute. While Icannot vouch for the accuracy of the data, Goode's is the onlyatlas I know with this information, a new feature with the 17thEdition. With a little care, your local coordinates can also beinterpolated to an accuracy of about ten minutes of arc using agood, detailed road map provided the map includes the fiducialmarks for longitude and latitude.

Use Function Key F6 to input your local coordinates andlocal place name; see also the section SETTING LOCAL COORDINATESfor a listing of the coordinates of selected cities in the UnitedStates and Canada. If your location is near one of the thesecities, the coordinates can be read directly from fileASTROCLK.CTY. The file is in standard ASCII code, and may beedited to include additional cities and locations using anyeditor provided the proper format is observed; WordStar and otherword processor users, use the ASCII or "Non-document" mode.

Both geographical and celestial data can be entered (anddisplayed) in several different formats. Celestial coordinatesmay be entered or displayed as degrees plus decimal degrees,degrees plus minutes and decimal minutes, or degrees plus minutesplus seconds and decimal seconds. All of these methods areacceptable to ASTROCLK although the separator varies (colon orcomma for times, comma for degrees and dates).

* * * * *

EUROPEAN USERS PLEASE NOTE

Both in this documentation and in program ASTROCLK itself,the period (point, ".") is used for the decimal point to separate

the integer and fractional parts of a number rather than thecomma (virgule, ",") as is the practice in many Europeancountries. This usage is sufficiently deeply buried in thesoftware that it is impractical to make it dynamicallyconfigurable. American users have to contend with dates enteredin the European style (DD,MM,YYYY), so I've managed to makethings a little inconvenient for everyone!

Egalement ici dans cette texte et en le programme ASTROCLK,le point (".") plutot que la virgule (",") est utilize pourseparer les deux parties d'un nombre, le nombre entier et le

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fragment. C'est usage commun ici aux Etats Unis. Domage, mais ilfaut que les Americains utilizent les dats comme les Europeennes(jour, mois, ans). C'est dificile pour tous le monde! [Traductiongrace a Dictionnaire Larousse, moins les accents.]

* * * * *

When ASTROCLK first starts, the current Local Standard Timeis displayed in the main window in large numerals. The numberkeys 0 through 9 (on the top row of the keyboard) and severalother keys select the display mode for the main window:

1 LST/LDT Local Standard/Daylight Time2 UTC Coordinated Universal Time3 LMST Local Mean Sidereal Time4 GMST Greenwich Mean Sidereal Time5 TDT/ET Terrestrial Dynamical/Ephemeris Time6 Perpetual Calendar7 Additional Date Information8 Precision Time and Data Displays9 Planetary Data Displays0 Celestial Tracking Display

T Interval Timer DisplayA Alarm Countdown Display [if Alarm is set]

Function Key F1 gives quick help for the function keys, butshould not be considered a substitute for this documentation.

Using Function Key F7, the information displayed on theTarget Tracking Display at the left of the screen can be switchedbetween several formats including whole units (hours or degreesas the case may be) plus decimal units, or a more conventionaldisplay (hours, minutes, seconds or degrees, minutes, seconds).Pressing ALT-F7 will change the Target Tracking Displaycoordinates from Right Ascension (hours) to Sidereal Hour Angle(degrees) and Hour Angle (hours) to Greenwich Hour Angle(degrees), forms preferred by navigators.

With the exception of the Julian Date (which is displayed tosix decimal places), the running clocks are displayed to thenearest second. Other data are displayed to 0.000001 degrees orhours, 0.0001 minutes of time or arc, or to 0.01 seconds of timeor arc, depending upon the display format selected with FunctionKey F7. The Precision Time Display (Display Mode 8) gives varioustime information to a precision (and approximate accuracy) of

0.0001 seconds. Most internal calculations are made inQuickBASIC's DOUBLE PRECISION data format to yield maximumaccuracy and precision, but not all data are necessarily accurateto the precision displayed. See the section PRECISION ANDACCURACY TESTS for additional information.

When the clocks are ON, ASTROCLK checks the system time andattempts to begin a new set of calculations each second. Sincethese calculations tend to be complex and time consuming, someslower computers may not finish the task within the allottedtime. My Zenith Z-183 laptop, running at 8 MHz but with no mathcoprocessor, skips every third or fourth second when operating in

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the Target Tracking Mode and the Precision Time and DataDisplays. This does not affect the accuracy of the displayeddata, only the frequency with which it is updated. Forcomparison, my old Zenith Z-151 running at 4.77 MHz but with an8087 math coprocessor, manages to keep up just fine. Regardlessof the computer type, a math coprocessor will substantiallydecrease computation times. See the performance comparisons inthe section HARDWARE REQUIREMENTS. Version 4.50 of Microsoft'sQuickBASIC, the programming language used for ASTROCLK,automatically senses the presence of a math coprocessor and usesit if it is available.

To exit ASTROCLK, press ESC and you will return to the DOSprompt. ASTROCLK always rewrites the file ASTROCLK.INI prior toexit in order to reflect the current coordinates, flags, displaymodes and other information. Each time ASTROCLK is started itchecks for file ASTROCLK.INI and reads its contents if present.If you change the coordinates, the new coordinates will be usedthe next time you run ASTROCLK.

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FUNCTION KEYS AND HELP

Function Key F1 invokes a HELP function which displays theoperation performed by the ten Function Keys, F1 through F10 (aswell as several ALT or SHIFT plus Function Key combinations).While the operations are generally self explanatory, positioningthe flashing red pointer at the desired operation (F1 throughF10) with the Up or Down arrow keys and pressing RETURN willdisplay additional information. Pressing the desired Function Keydirectly will also display the supplementary information for thatFunction Key. Press RETURN (or any other key) to return to themain HELP menu. Press the SPACE BAR to exit the main HELP menuand return to normal program operation.

All of the displayed clocks are stopped while using HELP andthe message "Clocks OFF" will be displayed in flashing red at theupper right of the screen. If the clocks were on when HELP wasrequested, the clocks will resume normal or simulated operationwhen you leave HELP and the message "Clocks ON" or "SIMULATION"will again be displayed in green or yellow respectively at theupper right of the screen. If the clocks were off when HELP wasrequested, they will remain off when you leave HELP.

The following operations are available with the ten FunctionKeys, F1 through F10:

F1 Display HELP screens. Display program name, version,and date if pressed again when the main HELP screen isvisible.

F2 Display Target Object EPHEMERIS. Before pressing F2,set the desired start time using F3, then select thedesired target object using F5. Press F2 and enter thedesired step interval and the number of intervals. Theephemeris information is displayed on the screen. Whendone or if more than 20 intervals are requested, thedisplay will pause; press any key to contiue. Use theSHIFT-PrtSc to obtain a printed copy of the ephemeris.

F3 Set LOCAL/UT TIME and/or LOCAL/UT DATE. The on-screenclocks are running when the time and date are set tothe system clock or when the SIMULATION mode has beenenabled with ALT-F4. (If the clocks are stopped, pressF4 to restart the clocks.) When entering time or date,press RETURN to skip an entry and leave that item

unchanged. F3 automatically cancels the SIMULATIONmode.

LOCAL/UT/TDT TIME: Enter as Hours, Minutes, Secondsusing 24 hour notation; use either the comma or thecolon as separator. Decimal fractions are permitted forany item. Add the letter "U" at the end of the entry toenter UT TIME instead of local time; add the letter "T"or "E" at the end of the entry to enter TDT/ET TIMEinstead of local time.

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NOTE: Use ALT-F10 to set the DAYLIGHT FLAG and anyrequired ZONE CORRECTION. See the section SETTINGPROGRAM OPTIONS for an explanation.

LOCAL/UT DATE: Dates may be entered in a number offormats. For "standard" dates, enter the new date inthe form DD,MM,YYYY. Note that the date is enteredEuropean style: Day, Month, Year and that the full 4-digit year is required. Years B.C. (Julian prolepticcalendar) are preceded by a minus sign (e.g. -4713).NOTE: There is no year 0000 in the day numberingalgorithms used in ASTROCLK. Add the letter "U"following the year to enter UT DATE instead of localdate. When UT TIME has been entered, UT DATE isautomatically entered rather than LOCAL DATE. Dates mayalso be entered as the Julian or Sidereal date. Fivestyles of day numbers may be used, selected by theprefix used, as well as several other methods.

For a more complete explanation of time and date entryusing F3, see the section SETTING LOCAL/UT/TDT TIME ANDDATE.

Use ALT-F3 to read the hardware clock with programRTCLOCK from within ASTROCLK. (See PROGRAM OPERATIONfor details.)

Use SHIFT-F3 to set an ALARM TIME or to set the starttime for the INTERVAL TIMER. The alarm may be set up to23 hours in advance. When set, a window appears at thelower right of the screen and displays the set alarmtime and the time remaining in red. To set the starttime for the Interval Timer, suffix the entered timewith the letter T. To disable an already set alarm,press SHIFT-F3 then press RETURN. See also the sectionALARM AND INTERVAL TIMER OPERATIONS for additionalinformation.

F4 Toggle Clocks ON or OFF. When clocks are ON, all timeand date displays are referenced to the computer'sinternal software clock and any manually set local timeor date is lost. When clocks are OFF, all times on thescreen are frozen. The clocks are automatically turnedOFF if either the local time or local date is set with

Function Key F3. The message "Clocks ON" (green),"Clocks OFF" (flashing red), or "SIMULATION" (yellow)appears at the upper right of the screen to indicatethe current clock status.

Use ALT-F4 to toggle simulated real time. First presetthe desired time and date using Function Key F3, thenpress ALT-F4 to turn on the simulation. The wordSIMULATION will appear in yellow at the upper right ofthe screen (in place of the Clocks ON/OFF message) whensimulation is active. Press ALT-F4 again to disable

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simulation. Function Key F3 also cancels the simulationmode. NOTE: Unlike the DOS clock, which may only be setfor the period 1980 through 2099, the internal ASTROCLKsimulation will operate for any time and date.

Function Key F4 may be used to start and stop theclocks in the simulation mode as usual. Function KeysF4 and ALT-F4 stop simulated time in different ways.When F4 is used to stop and start simulation, thesimulated time will resume as if the clocks had notbeen stopped (the same as in the real time mode). Useof ALT-F4 disables the simulation and stops the clocks;pressing ALT-F4 again will restart simulation at thecurrent indicated time. If F4 is pressed after ALT-F4has stopped simulation, normal real time operation willfollow.

F5 Set new star or celestial object TARGET COORDINATESusing either the internal star database or an externalstar catalog. [NOTE: To set the target coordinates fora planet or to use the external Minor Planet Catalog,see the sections PLANETARY DATA DISPLAYS and MINORPLANET SELECTION.]

A sub-menu is displayed offering the following functionkey selections:

F1 Enter the USNO Standard Navigational Star Number(1 through 57, or 0 for Polaris) or the desiredStar Name to use the internally stored star data.When the name is entered, upper or lower case maybe used and only sufficient letters tounambiguously identify the star name are required.Enter "Deneb " (with a trailing space) todistinguish that star from "Denebola".

F2 Search for nearest USNO Standard NavigationalStar. Enter the local horizon coordinates indegrees: ALTITUDE (the angle from the true horizonup to the star) and AZIMUTH (the direction of thestar in the sense North=0, East=90, South=180, andWest=270). The program will search for the USNOstar closest to the position specified and thedata for that star will be displayed in the

Tracking Window.

F3 Search EXTERNAL STAR CATALOG by star name, staridentification, or catalog number. When the nameis entered, upper or lower case may be used andonly sufficient letters to unambiguously identifythe star name are required. (Enter "Deneb ", witha trailing space, to distinguish that star from"Denebola".) Messier objects may be identified bycommon name ("ORION") or by Messier number ("M9").If the program finds a matching entry in the

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catalog, the data for that star will be displayedin the Tracking Window; if no match can be made,the data in the Tracking Window is left unchanged.Press SPACE BAR to cancel the catalog search inprogress; the current data is left unchanged.

F4 Search EXTERNAL STAR CATALOG by Right Ascensionand Declination. Enter the coordinates whenrequested and the program will find the catalogstars closest to the position specified. Respond"Y" to display the 10 closest stars or "N" to onlylocate the closest star. Press RETURN to displaythe star in the Target Tracking Window. PressSPACE BAR to cancel the catalog search inprogress; the current data is left unchanged.

F5 Search EXTERNAL STAR CATALOG for nearest star.Enter the local horizon coordinates in degrees:ALTITUDE (the angle from the true horizon up tothe star) and AZIMUTH (the position of the star inthe sense North=0, East=90, South=180, andWest=270). The program will search the catalog forthe stars closest to the position specified. Respond"Y" to display the 10 closest stars or "N" to onlylocate the closest star. Press RETURN to displaythe star in the Target Tracking Window. PressSPACE BAR to cancel the catalog search inprogress; the current data is left unchanged.

F6 MANUAL DATA ENTRY. Enter the celestial

coordinates, Right Ascension and Declination, theproper motion in Right Ascention and Declinationper Julian century (in seconds of time or arc),and the object name as requested. If the propermotion parameters are not known, press RETURN toenter zero. If RETURN is pressed for the objectname, the display will show "Manual Target Data".The data for the object will be displayed in theTracking Window.

RETURN Cancel entry of Target Coordinates, leave currentTarget Coordinates unchanged, and resume normalprogram operation.

When searching using local horizon coordinates,altitude is measured in degrees up from the truehorizon; 0 degrees is the horizon and 90 degrees isdirectly overhead. Don't forget to take into accounthills or other obstructions that may obscure the truehorizon. Azimuth is measured in degrees from true Northin the sense NESW; thus, 0 degrees is North, 90 degreesis East, 180 degrees is South, and 270 degrees is West.

The star selection algorithm used in the varioussearches attempts to pick the Standard Navigational

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Star or external catalog star which is closest (angulardifference) to the coordinates you have entered. It maytake a little practice before you can look at the nightsky and estimate star positions accurately enough forthe program to select the correct star. While thesearch is in progress, the message "SEARCHING ..." willappear at the upper right of the screen and the clockswill temporarily be stopped.

For an external catalog search, file ASTROCLK.CAT mustbe present. This catalog includes data for 1645 stars,Epoch J2000.0, extracted from USNO STAR1.CAT and USNOMESSIER.CAT. Stars may be requested by catalog numberor by any of several names. See the section USINGEXTERNAL STAR CATALOGS for additional information.While the search is in progress, the message "SEARCHING..." will appear at the upper right of the screen andthe clocks will temporarily be stopped.

NOTE: The supplied external star catalog is a largefile, currently about 160Kb, and the search time on afloppy disk system is rather slow; the numbersappearing during the search indicate progress throughthe catalog in increments of 50.

For manual data entry, you must know the standardequatorial coordinates, Right Ascension andDeclination, for the celestial object you wish totrack. Star Atlases, astronomical magazines, and otherpublications usually give the coordinates for objectsof interest. The input routine is very flexible anddata may be entered in a number of formats. Observe theseparator requirement: items for time (including RightAscension) must be separated by the colon or comma,while items in degrees (including Declination) must beseparated by the comma. In general, only the first item(hours or degrees) is required and a decimal fractionis allowed for all items. If you press RETURN for anitem, the data for that item will be left unchanged.

When entering data manually, the parameters for propermotion are requested. Press RETURN to enter zero. Thesedata are used by ASTROCLK to calculate the currentapparent equatorial coordinates on the Tracking Display

and are also used if the coordinates are precessed fromone epoch to another using Function Key F8. Thisinformation is given for many stars in star catalogssuch as SKY CATALOGUE 2000.0. However, note thatASTROCLK requires this information in SECONDS PERJULIAN CENTURY (36525 days) and not all references usethe same units; SKY CATALOGUE 2000.0, for example, usesSECONDS PER YEAR which must be converted prior to inputinto ASTROCLK.

ALT-F5 Because of its usefulness, the coordinates of the star

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POLARIS (Alpha Ursa Minoris), the pole star, are hardcoded into ASTROCLK on Function Key ALT-F5. POLARIS isoften used for navigation and for the initial alignmentof celestial telescopes and satellite dishes. Pressthis key and the coordinates for POLARIS areautomatically entered and the display mode is switchedto the Target Tracking Display.

F6 Set new LOCAL COORDINATES. All entries are in degreesand require the comma as separator between the items. Adecimal fraction is allowed for any item, and only thefirst item (degrees) is required. See the sectionSETTING LOCAL AND DESTINATION COORDINATES for details.

If file ASTROCLK.CTY (or an alternate city file) ispresent, it may be used to read the coordinates for aselection of cities. Enter the name of the locationdesired in upper or lower case. Only letters sufficientto uniquely identify the location are required. PressRETURN to ACCEPT the displayed location; press SPACE tosearch for the next match. Press ESC during the searchto cancel the search and leave the local coordinatesunchanged. If no match can be found, a CAUTION messagewill be displayed at the lower left of the screen.Press RETURN to continue; the local coordinates will beleft unchanged.

To enter coordinates manually, press RETURN whenprompted for the name. Then enter the LONGITUDE,LATITUDE and ELEVATION, followed by the NAME of thelocation.

NOTE: Additional city files may be available from timeto time on my BBS or by mail; see the end of thesection A BRIEF EDITORIAL for the BBS telephone numberand my address.

SHIFT-F6 Set DESTINATION COORDINATES for use with navigationfunctions. Operates in all respects like F6 aboveexcept that the destination coordinates are set ratherthan the local coordinates, and you may enter "*"instead of a name to set the DESTINATION coordinates tothe current LOCAL coordinates.

ALT-F6 Set LOCAL CONDITIONS for Elevation, Temperature, andPressure. Allows the user to set these conditions todetermine horizon dip and refraction. Automatic con-version between metric and English units is performed.

F7 Set DISPLAY FORMAT for the main display window and LocalCoordinates window. When the program is started, allangles and times on the main display window (other thanlarge character times) and in the Local Coordinateswindow are shown in Degrees/Hours-Minutes-Seconds

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format. Press F7 to cycle between display formats; thethree available formats are:

ANGLES TIMES------------ -----------DDD MM SS.SS HH:MM:SS.SSDDD MM.MMMM HH:MM.MMMMDDD.DDDDDD HH.HHHHHH

Press ALT-F7 to change Target Display coordinates fromRight Ascension (hours) to Sidereal Hour Angle(degrees) and from Hour Angle (hours) to Greenwich HourAngle (degrees), preferred by navigators and given inreferences such as the Astronomical Almanac. Press ALT-F7 again to return to the original format. Declinationis not affected. See also the section TARGET TRACKINGDISPLAY for further discussion.

F8 PRECESS Internal Star Database. This function allowsthe user to precess (adjust for different epochs) thecurrent target data and the preset star database in theprogram. Upon startup, all data are set for epochJ2000.0, the current standard epoch. Press the "Y" keyto make the precession calculations or press RETURN tocancel the calculations and leave all data unchanged.

If you proceed, press RETURN to restore all data toEpoch J2000.0 or enter the desired new epoch. The newepoch may be entered in any of the following formats:

dd,mm,yyyy Calendar DateJDnnnnnnn.nnnnnn Julian DateDJDnnnnnn.nnnnnn Julian Date (J1900.0)MJDnnnnnn.nnnnnn Modified Julian DateJyyyy.yyy Julian EpochByyyy.yyy Besellian Epoch+nnn Add nnn days to Current JD-nnn Subtract nnn days from Cur JD* Current Julian Date and Time# Current Julian Date @ 0h UT

Lower case letters (yyyy, nnnnnn, etc.) representnumbers while upper case letters (JD, J, etc.) are usedto designate the data format being used. The calendar

date method assumes the Julian or Gregorian calendar asdetermined by the date and the Calendar Flag (See ALT-F10, Setting Program Options). Except for the calendardate method, any number of digits to the right of thedecimal point may be input although more than about sixwill not be significant. Regardless of the data formatused for input, the date is internally converted to thecorresponding Julian Date for use in the precessioncalculations. The current ASTROCLK internal databaseepoch is always shown in the Target Tracking Display,Display Mode 0, and in the initial Precession

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instructions when using Function Key F8.

Care should be taken when manually entering data whoseepoch is different from that of the internal database.In order to maintain consistent data within ASTROCLK,the internal star database should first be precessed toa data epoch, then manual data referenced to that epochshould be entered. After that, all data may beprecessed to the final epoch; using this procedure,both the manually entered data as well as the internaldata will always refer to the same epoch.

For example, to track a target using Epoch J2000.0coordinates when the available catalog data is forEpoch B1950.0, first precess the internal star data toB1950.0 using F8, next enter the target RightAscension, Declination, Name from the catalog, and theproper motion in Right Ascension and Declination (ifknown) using F5 (and F6 for manual entry). Finally,again use F8 to precess all data back to Epoch J2000.0(or any desired epoch). Thereafter, F8 may be used asmany times as desired to precess the database.

F9 DOS SHELL. This function invokes a copy of the MS-DOSexecutive, COMMAND.COM, and allows the user to enterany legal DOS command. COMMAND.COM must be available orASTROCLK will ignore the request and continue normaloperation. Since COMMAND.COM must reside in availablememory in addition to ASTROCLK, use of a large RAM DISKor TSR program may cause the DOS shell to fail. The MS-DOS prompt is displayed and the computer performs inmost respects exactly as usual. However, far lessmemory is available and therefore programs whichrequire very large amounts of memory for theirexecution may not operate properly with the SHELL.

Enter EXIT to return to ASTROCLK and resume operationwith all data and parameters unchanged.

SHIFT-F9 may be used to automatically executa a presetDOS command or batch file. The DOS command is set usingALT-F10, SETTING PROGRAM OPTIONS, and is saved in fileASTROCLK.INI. If a DOS command has been set, thecommand is executed and upon completion ASTROCLK is

automatically resumed. This command has the samerestrictions and comments as the normal F9 commandabove; the only difference is the execution of a presetDOS command and automatic return to ASTROCLK. Thedefault is no action.

ALT-F9 may be used to automatically execute the USNOInteractive Computer Ephemeris (ICE) or the USNO FloppyAlmanac (FA); see the section USNO EPHEMERIS PROGRAMSfor more complete information. ALT-F9 will execute theselected USNO program if the appropriate software has

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been installed in the computer AND if the appropriateephemeris has been selected and its path set using ALT-F10, SETTING PROGRAM OPTIONS.

F10 Function Key F10 provides navigational calculationsusing two methods: DEAD RECKONING and SIGHT REDUCTION.For an observer in motion, ASTROCLK also calculates thecurrent position based upon the last "fix" and theobserver's course and speed. See the section CELESTIALNAVIGATION for details.

ALT-F10 is used to set or change various ASTROCLKprogram options. See the following section, SETTINGPROGRAM OPTIONS, for details.

0-9 Select Display Window Mode. The system starts out withLOCAL STANDARD/DAYLIGHT TIME displayed in largecharacters. In the United States, the correct time zonename (i.e. "PACIFIC") replaces the word "LOCAL". Pressthe number key associated with each display mode tochange to that mode. (Use the numbers at the top of thekeyboard rather than the number keys on the keypad atthe right unless NUMLOCK is ON.) The available numericmodes and alphabetic commands are:

1 Local Standard or Daylight Time (LST/LDT)2 Coordinated Universal Time (UTC)3 Local Mean Sidereal Time (LMST)4 Greenwich Mean Sidereal Time (GMST)5 Local Mean Solar Time6 Perpetual Calendar7 Julian Date Information8 Precision Time Display9 Planetary Data0 Target Tracking Display

N Select NAVIGATION Display Mode

P Select PLANET or MINOR PLANET(forces display mode 9 or 0)

A Alarm Countdown *S Start/Stop Interval Timer *T Interval Timer *

Z Stop and Reset Interval Timer *

* See the section ALARM AND INTERVAL TIMEROPERATIONS for information on these modes.

While in display mode 0, Target Tracking, use the UPand DOWN arrow keys to select the next or the previousStandard Navigational Star. PgUp and PgDn increase ordecrease the selected star number by 10. Use F5 toinput a new star number directly.

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While in display modes 1 through 5, the large clockdisplays, use the UP and DOWN arrow keys to select thedual-time displays and the HOME key to return tosingle-time display. See the section DUAL-TIME DISPLAYSfor further information.

While in display mode 6, Perpetual Calendar, use theLeft and Right arrow keys to change months, the Up andDown arrow keys to change years, and the PgUp and PgDnkeys to change the years by decades. HOME returns thedisplay to the current system date. Use F3 to input anew date or time directly.

While in display mode 8, Precision Time and DataDisplays, press PgUp or PgDn to view the next PrecisionTime or Data Display. See the section PRECISION TIMEAND DATA DISPLAYS for details.

While in display mode 9, Planetary Data, use the UP andDOWN arrow keys to change planets. See the sectionPLANETARY DATA DISPLAYS for further discussion.

Pressing "N" to select the Navigation Mode Display willresult in an error message if navigation has not beenenabled with Function Key F10. See the sectionNAVIGATION for further discussion.

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SETTING PROGRAM OPTIONS

Several ASTROCLK program options can be set using FunctionKey ALT-F10. The options which can be set are: DAYLIGHT FLAG,ZONE CORRECTION, COLOR FLAG, ICE/FA Flag, CALENDAR FLAG, externalFILE NAMES and PATHS, and PRESET DOS COMMAND. All of thisinformation is saved in file ASTROCLK.INI.

The DAYLIGHT FLAG determines whether or not Daylight Time isin effect. The ZONE CORRECTION allows the user to adjust for timezones which do not agree with the calculated values. The CALENDARFLAG determines which of three calendar conventions to use; it isinitially set to the Gregorian Calendar (from October, 1582). Asub-menu is displayed when using ALT-F10 with the current valuesshown enclosed by square brackets, "[...]". Press the functionkey corresponding to the option you wish to change or pressRETURN to resume normal program operation with the options asshown. A typical display showing the default values for each itemis shown below:

F1 DAYLIGHT FLAG: [OFF]F2 ZONE CORRECTION: [0.00]F3 COLOR FLAG: [ON]F4 ICE/FA FLAG: [0=ICE/FA Disabled]F5 CALENDAR FLAG: [1=Gregorian @ 1582]F6 SET FILE NAMES & PATHSF9 SET DOS COMMAND

(no command has been entered)RETURN Resume normal program operation

When all changes have been made and the informationdisplayed on the menu is correct, press RETURN to resume normalprogram operation. When you exit ASTROCLK, these options will besaved in file ASTROCLK.INI and will automatically be restored thenext time you run the program.

Setting the DAYLIGHT FLAG-------------------------

The DAYLIGHT FLAG selects whether or not an additional hourwill be automatically added during the time zone calculation todetermine Coordinated Universal Time. The flag applies equally toall time zones and the window label for local time will includethe word STANDARD if the flag is OFF, or the word DAYLIGHT if the

flag is ON. For example: PACIFIC STANDARD TIME or PACIFICDAYLIGHT TIME. If you wish to change the state of the flag, pressFunction Key F1. The DAYLIGHT flag is OFF by default. Because thedate of switching to and from daylight time are different indifferent countries and are sometimes changed for one reason oranother, ASTROCLK does not automatically set the state of theflag. If the UT TIME ZONE OFFSET has been enabled, be sure tocorrect that value using F10 when the DAYLIGHT FLAG is changed.

If the DAYLIGHT FLAG is incorrectly set, all calculatedtimes and positions will also be incorrect. Do NOT use theDAYLIGHT FLAG to adjust for an incorrect zone calculation; use

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the ZONE CORRECTION (see the following item) for that purpose.You may, if you prefer, leave your computer clock always set tolocal STANDARD time and the DAYLIGHT FLAG always off. However,you may NOT set your computer clock to UTC (unless you are inthat time zone); set the computer clock correctly and use displaymode 2 to view UTC instead.

Setting the ZONE CORRECTION---------------------------

The ZONE CORRECTION allows the user to make specialadjustments in the calculation of Coordinated Universal Time(UTC) relative to Local Time. Some time zones are not an integralnumber of hours offset from UTC; in other cases the actualstandard time for a particular location is different from thatcalculated by ASTROCLK because of the irregular way time zoneshave been defined locally. Some countries use "Double SummerTime" which is two hours ahead of the standard time for the zone.To change the current ZONE CORRECTION, press F2. The correctionmust be entered in hours and decimal fraction, H.HH or -H.HH, andis automatically rounded to the nearest 0.25 hours (15 minutes);the maximum correction is restricted to the range -2.00 hours to+2.00 hours. The ZONE CORRECTION is calculated in ADDITION to theDAYLIGHT FLAG.

IMPORTANT NOTE: Unlike the Daylight Flag, which remainsunchanged when you change local coordinates, the Zone Correctionwill be reset to 0.00 hours any time you change the localcoordinates on the assumption that the Zone Correction isunique to a given location. This also assures that when usingthe external city file to change cities and load the coordinatesfrom the file, the Zone Correction will be reset. The defaultvalue for the Zone Correction is 0.00 hours.

Setting the COLOR FLAG----------------------

The COLOR FLAG allows you to switch between color, red,green, and monochrome display. The COLOR mode uses various colorsfor the display. The RED option sets all screen colors to red inorder to protect night vision if the computer is operated in adarkened area. The GREEN option sets all screen colors to green;this may help reduce eye fatigue during extended use. The OFF(monochrome) mode is useful if you wish monochrome display orwhite display on color monitors. Switching to any of the color

modes on some true monochrome systems may cause an error. Seealso the section PROGRAM OPERATION for additional information onthe command line color options.

To change the COLOR FLAG from one mode to the next, pressFunction Key F3; the color changes for the new mode will takeeffect immediately within the window but the balance of thedisplay will not be affected until you leave the Setting ProgramsOptions window by pressing the RETURN key.

The state of the COLOR FLAG is saved in file ASTROCLK.INIand the program will use the previously set color mode the nexttime it is run. However, the command line color option (/M, /R,

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a modern date with the CLOCKS OFF will leave the Julian Dateunchanged but will change the calendar date to a new value,correct for the strict Julian Calendar. However, if the clocksare ON, they will automatically be set to OFF and a warningmessage will be displayed. If you wish to use the program withthe Julian Calendar and the clocks running, use the SIMULATIONmode.

Setting the FILE NAMES and PATHS--------------------------------

In order to execute the help function and to utilize theexternal data files and the USNO Interactive Computer Ephemeris(ICE) or Floppy Almanac (FA), ASTROCLK must know what the filenames are and where to find them. The default condition is thatthese files are all located in the current directory and that thefiles have the following names:

ASTROHLP.EXE External Help ProgramASTROCLK.CAT External star catalogASTROCLK.MPC External minor planet catalogASTROCLK.CTY External city fileICE.EXE USNO Interactive Computer EphemerisFAnn.EXE USNO Floppy Almanac (nn=88-99)

There is a different file for each year for the USNO FloppyAlmanac. All files required by ICE or FA must be located in thesame directory as the .EXE file. A common drive and path may bespecified in the command line when starting ASTROCLK for thefirst time.

********************* IMPORTANT NOTE *********************

Once ASTROCLK has been executed the first time, the driveand path information are saved in the program initializationfile ASTROCLK.INI. Thereafter, ASTROCLK uses the informationin ASTROCLK.INI and overrides any drive or path specificationentered on the command line. You may use ALT-F10 and then F6 tochange the drive and/or subdirectory from within ASTROCLK, or youmay delete file ASTROCLK.INI at the DOS prompt to start over.

* * * * *

Since two of the external data files, ASTROCLK.CAT andASTROCLK.CTY, are conventional ASCII files which may be edited bythe user, a provision is included here to permit the user tospecify an alternate file name for either of these files,including drive and path. For example, you might wish to use aspecial city file when traveling in Europe. More ambitious usersmay wish to prepare their own external star catalogs.

The current STAR CATALOG, MINOR PLANET CATALOG, and CITYFILE names are shown on the menu, in that order. If a driveand/or path was specified with the command line, they will also

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SETTING LOCAL/UT/TDT TIME AND DATE

ASTROCLK has three basic modes of operation: real time,simulated real time, and static. In the real time mode, theclocks are running synchronized to the system clock and the datadisplayed are calculated every second (computer calculation timepermitting). The simulation mode is the same as real time exceptthat ASTROCLK uses a time previously set with Function Key F3 asits reference. Using a Zenith Z-183 laptop computer not equippedwith a coprocessor, ASTROCLK is able to make most calculations(except for Tracking and Precision data) within one second.Compared to a Zenith Z-248 8 MHz AT-compatible computer with amath coprocessor, the computational delays are noticeable.Provided the local time, date and coordinates have been properlyset, the data reflect the correct real time (or simulated realtime) parameters. In the static mode, the data are held at thevalues for the specified time.

Except in the Navigation Mode, an algorithm is used toautomatically calculate the time offset from UTC, CoordinatedUniversal Time based upon the longitude of the local coordinates.UTC is roughly equal to Greenwich Mean Time (GMT) for years 1925and later. The results of this calculation are shown as UTC ZONE(for example, -118 degrees yields UTC -8.0 for Pacific StandardTime in Southern California), and are used in all subsequent timeand position calculations. All calculations are based uponStandard Time. If Daylight Time is in use AND your computer clockis set to Daylight Time, use Function Key ALT-F10, SETTINGPROGRAM OPTIONS, and set the DAYLIGHT FLAG ON to automaticallyadjust the times. To return to Standard Time, set the DAYLIGHTFLAG OFF. ASTROCLK does not perform any date tests to verify thevalidity of the DAYLIGHT FLAG setting.

Because of the strange ways time zones have been drawn, theautomatic time zone calculation may not always produce thedesired result. The calculated time IS the correct time basedupon the division of the world into 24 equal time zones. However,for political reasons or for local convenience, time zones oftendo not excatly follow the designated meridians. If a location ismore than 7-1/2 degrees East or West of the 15 degree meridiancorresponding to the local standard time, the time calculationswill be an hour in error. Use the ZONE CORRECTION with ALT-F10,SETTING PROGRAM OPTIONS, to correct for this problem to thenearest fifteen minutes. Some time zones are not set at anintegral number of hours offset from UTC, fortunately none of

them in the United States. A correction of from -2.00 hours to+2.00 hours will be accepted in order to accommodate both timezone errors and double daylight times. For U.S. locations notrequiring this special correction, ASTROCLK will automaticallydisplay the correct zone name, Eastern, Pacific, etc.

In the Navigation Mode, the calculation of times is handledslightly differently. Because the computer may move from one timezone to another, the Navigation Mode requires that the UT TIMEZONE OFFSET, the difference between the computer's clock andUniversal Time (UT), be entered using Function Key F10. ASTROCLKthen automatically converts the computer clock to UT before

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making adjustments for the current longitude (whether calculatedor manually entered). This permits the computer to move freelyfrom time zone to time zone without resetting the computer'sinternal clock. However, there is as usual no free lunch; becausethe local time is strictly dependent upon the current longitude,no ZONE CORRECTION for time zones which do not correspond to thecalculated time is permitted. Any ZONE CORRECTION in effect whenthe UT OFFSET is set will be cleared. On the other side of thecoin, once the UT OFFSET has been set ASTROCLK's localcoordinates may be set as desired and the current correct localtime will be calculated and displayed and UT TIME will remainconstant. ASTROCLK will adjust ALL local times by one hour if theDAYLIGHT FLAG is set; given that the dates when daylight time isin effect vary considerably around the world, users may find itmore convenient to leave the DAYLIGHT FLAG off when away fromtheir "home" time zone(s), turning it on only when certain of thelocal standard. See also the discussion of the UT TIME ZONEOFFSET in the NAVIGATION section.

When used in the static mode, the clocks are stopped. Theuser may enter any desired location or time/date and allcalculations will be made using that data. Note that Westlongitudes and South latitudes must be entered as negativenumbers for ASTROCLK. (CAUTION: Some texts and institutions donot observe the same sign conventions!) The basic calculations inASTROCLK are based upon formulae accurate for Epoch J2000.0.Negative dates, that is dates "B.C.", display in RED (BLINK inall monochrome modes) and there is no year 0000; the sequence ofyears near zero is -2, -1, 1, 2, etc. The accuracy of some of thecelestial data will decrease as the time difference from EpochJ2000.0 increases.

Although UTC and UT (=UT1) are not the same, they aremaintained to within 0.9 seconds of each other by the occasionalinsertion of Leap Seconds at the end of June or December. In 1988the difference is typically less than 0.2 seconds. While softwareprograms are available to precisely set a computer's clock usingtelephone signals from NBS, this accuracy cannot usually bemaintained for extended periods of time. In any event, frequentcalls to NBS are impractical for most of us by reason of cost. Amore cost effective solution is to use the Heath/Zenith GC-1000Most Accurate Clock and its optional software to synchronize thecomputer's clock. The GC-1000 is a combination receiver and clockand when equipped with an RS-232 interface and external antenna,it can maintain UTC time to within 10 milliseconds.

I have therefore elected to treat UTC as equal to UT for

time and date displays and have actually assumed UT time and datein all but one case: the correct UTC time relative to UT iscalculated and displayed on Precision Time Display #1 but it isotherwise not used. All other times and dates are referenced toUT rather than to UTC. This minor technical error represents acompromise between technical accuracy and ease of use.

While the times displayed by ASTROCLK in the various smallwindows are rounded to the nearest second, any time (Local, UT,or TDT) may be entered using Function Key F3 to a precision ofapproximately 0.0001 seconds and will be used to that precisionin the various calculations. Compare the times shown in the small

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windows with those in the Precision Time Display #1. Except forsome items in the Precision Time Displays, this additionalprecision is usually not significant. See the section PRECISIONAND ACCURACY TESTS for additional comments.

Setting the LOCAL/UT/TDT Time

The time entry format is very flexible and for conveniencewill accept either the traditional colon (":") or the comma (",")as the separator between hours and minutes or minutes andseconds; the examples are shown with the colon only. Each item(hours, minutes, or seconds) can accept a decimal fractionalthough normally only the last item entered would have afractional part. Time entries are ALWAYS made using the 24-hourconvention. The following are all acceptable time entries:

HH HoursHH.HHHHHH Hours + fractional hoursHH:MM Hours:MinutesHH:MM.MMMM Hours:Minutes + frac minsHH:MM:SS Hours:Minutes:SecondsHH:MM:SS.SS Hours:Minutes:Seconds + frac

The "standard" date input format requires the day, month,

and year (in that order, European style, and separated by commas)in either of the following two formats:

DD,MM,YYYYDD.DDD,MM,YYYY

The first format specifies the date to be used with the existingor just input time; unless the letter "U" or "T" has beenappended to the time input (see below), the date is the LOCALdate. The second format, containing a fractional day (including"." alone or ".0") specifies a UT date with the time implicit toallow the astronomical convention where dates are often given inthe form "1988 JAN 1.5"; this would be entered as "1.5,1,1988".The time input is ignored with this format (press RETURN). Thefractional part may have as many digits as desired, but more thanabout six digits usually are not significant.

It is sometimes convenient to set the time and date usingUT (=UT1) data. This avoids having to make the conversionsmentally. If you add the letter "U" at the end of the time or

date entry, ASTROCLK will perform the appropriate time or dateconversions automatically, based upon the current settings of theDAYLIGHT FLAG and ZONE CORRECTION. If you add "U" to your timeinput to enter UT time, ASTROCLK assumes that you are alsoentering UT date. If you enter a fractional part of a day as partof the date input, the time input is ignored and UT date isassumed (see the preceeding paragraph).

As an example, to set the time and date to 9:44:30 UT onNovember 13, 1978, use the following entries:

9:44:30U (UT time)

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13,11,1978 (UT date)

Alternatively, the same time and date may be input by pressingRETURN for the time, and using the following date entry (with thefractional part of the day representing the desired time):

13.405903,11,1978 (UT date, time implicit)

If Terrestrial Dynamical Time (or Ephemeris Time prior to1984) is desired, add the letter "T" (or "E") at the end of thetime entry. ASTROCLK automatically selects TDT or ET based uponthe date regardless of the letter used to designate the timeduring input. Note that the displayed UTC DATE may not correspondto that input if the time is within the period Delta T (TDT-UT)of midnight. ASTROCLK automatically adjusts the date to agreewith the information input and near midnight this can beconfusing to the user!

Setting the LOCAL/UT Date

The date input routine will also permit the entry of theJulian Date (JD), Dublin Julian Date (DJD), Modified Julian Date(MJD), Truncated Julian Date (TJD), or Greenwich Sidereal Date(GSD) by prefixing the date with the appropriate two or threeletters followed by the desired date. Whenever letters are used,they may be input in upper or lower case. Note that when aninteger GSD is enter

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