Ephemeris

Download my freeware ephemeris program, you'll find this simple program has some very useful features.

- Positions for the Sun, Moon, planets, comets and minor planets
- Easy input of orbital elements
- Produce tables of up to 2000 positions for any time interval and twilight setting, ideal for comets
 
The algorithms are based on Jean Meeus' work published in Astronomical Formulae and thus produce excellent positional accuracy, typically to 1 arc second. Recently added is the ability to export the planets positions and a comet or minor planet to 'planets.dat' which can then be used by Mel Bartels scope.exe program which computer controls a telescope.

Download The Program (299Kb zip file)

About Ephemeris
 Hints & Tips
 Export Planets.dat for use in Mel Bartels scope.exe
Known limitations

Unzip the 'astro.zip' file after downloading and extract into a temporary directory.
Use the install.exe program to install into a directory of your choice.
Should you find problems with the install routine then simply locate the files as follows:

All *.dat files in c:\windows folder
astro.exe any folder, this must be the same folder as scope.exe if you are using Mel Bartels software and want to use the 'export data file ' option to generate planets.dat otherwise planets.dat will be exported to the same folder as astro.exe.
vbrun200.dll and grid vbx in \windows\system

About ephemeris

The program was gradually developed from about 1989 onwards using gwbasic, later qbasic and this version using MS Visual Basic during 1994 to 1996. Most development stopped in about 1997 and will not go any further than this version. 

All of the astronomical routines are based on Jean Meeus' excellent books Astronomical Formulae for Calculators and  Astronomical Algorithms. The results are therefore excellent for most objects, typically accurate to 1 arc second or so when compared to the Astronomical Almanac. The program has been in use for some years by  Liverpool Astronomical Society members and has not shown up any significant errors of accuracy during this time (see known limitations)

Hints & Tips

I never got around to a help file - sorry - this is the best there is, feel free to e-mail me with any problems.
The program is largely self explanatory since it is simple, however the following may help. 

  • When Ephemeris starts the system date & time are read along with the default position and an epemeris is generated. To change your default position click on the Earth icon for date & time settings.
  • An ephemeris for any object is accessed by clicking on it's icon on the toolbar or selecting it from the View menu
  • Click on the leftmost labels (which highlight) to show different summary details in the right hand pane, eg clicking on 'dec' will show a listing on the right of all the declinations of the sun moon and planets.
  • The default comet or minor planet is set by entering the dialog box for orbital elements
  • One of the strengths of the program is the ephemeris generation in 'tabulate'. This screen shows a blank table to start with. Set up your ephemeris style by clicking on each of 'headings', 'twilight', and date & time.
  • When all of these have been entered click on the object icon of your choice and an ephemeris will be generated.
  • A very useful feature is the ability to tabulate positions for a set twilight, ie the daily time changes but the degree of twilight remains the same. This was designed for comet observation and works very well and as far as I am aware is not found in any other ephemeris or planetarium program.
  • You can generate as many different ephemerides on the screen as you like by choosing File...New Window, then generate an ephemeris for another object. The windows can then be tiled or cascaded using the Windows menu.

Generating Planets.dat

A text file containing the names and positions of the planets and one chosen comet can be generated from the program for use with Mel Bartels excellent computer controlled telescope system. Scope.exe uses 'planets.dat' when you select planets from the datafile menu. To generate the file from Ephemeris hit F3 or File...Export Data File menu. The datafile 'Planets.dat' will be created in the same directory as Astro.exe which should be in the same folder as scope.exe for the data file to be recognised.

Known Limitations

I will not develop this program any further. However I would like to know of any serious bugs in the numerical accuracy - but less bothered about graphical problems etc., e-mail me if you think you find any major problems.

These are the limitations I know about.

  • The magnitude of Saturn does not account for the ring system and so is too faint at any time, I will correct this sometime.
  • There is a tiny discrepancy between the geocentric and topocentric positions of Pluto.
  • The program was designed for a 640x480 display only but will run with higher level displays.
  • The lower darkness duration bar may be obscured by the task bar in Windows 95/98 at VGA resolution
  • When comparing positional accuracy with the astronomical almanac please remember to compare geocentric coordinates only.