Comets

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Download New Comet Data

When calculating comet positions it's important to use up-to-date orbital elements. Not only are new comets constantly being discovered, but orbital elements for comets slowly change with time, and can only be used reliably for a few weeks.

The organization responsible for coordinating new comet discoveries and producing authoritative orbital elements is the Central Bureau for Astronomical Telegrams. They kindly make these element sets available in a format directly suitable for use by a number of different astronomy programs, including SkyMap and SkyMap Pro. To download the latest element set and prepare it for use by SkyMap or SkyMap Pro, proceed as follows:

Downloading comet data for SkyMap Pro

  1. Follow this link to display the latest set of comet element data in SkyMap's data format.
  2. Save the page as an ASCII text file on your computer. This can have any desired name, but should have an extension of ".cat". You may wish to following the naming convention used for the files supplied with SkyMap Pro, which is to use a name of the form YYYYMMDD.cat, representing the date on which the elements were downloaded, eg "19980215.cat" for an element set downloaded on Feb 15th, 1998.
  3. Edit the file previously saved using any convenient text editor (eg Windows "NotePad"), and delete any blank lines which may be present at the beginning and the end of the file.
  4. Follow the instructions given in the SkyMap Pro manual to load the new catalog.

Note that if you are using SkyMap Pro 10 or later and are connected to the Internet, you can use the Tools/Download Data menu item within SkyMap to download up-to-date comet data at any time.

NB: The download link for comet orbital elements has changed since the program was released. If you get an error trying to download orbital elements from the program, select the "File/Preferences/Downloaded Data" menu item, and set the URL for downloading comet data to:

http://www.minorplanetcenter.org/iau/Ephemerides/Comets/Soft01Cmt.txt

Downloading comet data for SkyMap

  1. Follow this link to display the latest set of comet element data in SkyMap's data format.
  2. Save the page as an ASCII text file called "comet.sky" on your computer.
  3. Edit the file previously saved using any convenient text editor (eg Windows "NotePad"), and delete any blank lines which may be present at the beginning and the end of the file.
  4. Copy the file to the directory in which SkyMap has been installed, overwriting the previous "comet.sky" file.

When you next run SkyMap, the new orbital elements will be available for use. Note that you will have to use the Options/Comets...menu item to select the comets you wish to display on the map.

Previous Comet Orbital Elements

Some historic orbital elements are available here.

Last Modified Mar 21, 2010