Plotting Asteroid Occultation Paths with Occult


You should use the latest version of Occult. As of the end of March 2001, the latest version is version 1.4 with the March 2001 revision to the asteroid prediction files. The March 2001 upgrade adds the ability to keep two separate sets of asteroid elements: the Main file of asteroid elements and the User file of asteroid elements. For the most accurate path predictions you must enter the asteroid elements in the user file and the epoch of these elements must be very close to the time of the occultation event.

I have installed the Goffin star catalog for Occult. The Goffin catalog is not necessary but it will occasionally save time. As of March 2001, the Goffin catalog distributed with Occult includes accurate positions for the Hipparcos stars but the Tycho data is Tycho-1 and is not as accurate as the newer Tycho-2 catalog positions. For this reason, I always look up the star's positional information from the Tycho-2 catalog for my updates. The update summaries will include the star's position for the time of the event based on either Tycho-2 or Hipparcos catalog data.


  1. Enter the asteroid elements in the User file of asteroid elements. Note: the best method is to open the User elements dialog (from the Asteroids program main screen, under Asteroid elements), import the asteroid's elements from the main file, then edit the elements to change them to the updated values. Note: You MUST use a set of elements with an epoch within a few hours of the event and the epoch must be TDT (Terrestrial Dynamical Time). Unless stated otherwise, the asteroid elements distributed with IOTA updates should be TDT based.
  2. Enter the star position, as a one-off star, in J2000 coordinates with proper motion to the date/time of the event. The asteroid update summary and all Occult plots include the star's position in J2000 coordinates with proper motion to the time of the event (based on Tycho-2 / Hipparcos)..
  3. Search for the occultation using the USER elements and the ONE-OFF catalog.
  4. Plot the occultation path from the occelmnt.* file generated in step 3.



Page last updated: Apr 5, 2001.

Questions? contact Steve Preston