Asteroid Occultations

Since I have a degree in astronomy, I had to write about this one. A couple of weeks ago Google Maps Mania published an article about a Google Maps mashup (custom application) which allows you to see the tracks of Asteroid Occultation viewing paths. Not only did the author of the site allow you to view the paths in Google Maps, but he also creates Google Earth KML files so you can view them in GE.

First, you are probably wondering what is an asteroid occultation? Briefly, an asteroid occultation is when an asteroid passes in front of another stellar body (usually a star). In some cases you might see a star get dimmer, but in most cases you would probably need a telescope to witness the event. An asteroid ocultation viewing path is where on the Earth that occultation would be visible. If you have ever seen the viewing path maps drawn for a solar eclipse, this is the same concept.
After you go to the asteroid occultation maps page, scroll down to an upcoming date in the table titled “Asteroidal Occultations Visible from North America” (unfortunately, this is the only area he covers for now). Then select an appropriate asteroid (say today’s (850) Altona). Below the map you will see a link to “Download a-ready-to-use Google Earth points file (track.kml) for this event.” Or, you can just click here to see it now .
The asteroid occultation maps were created by Charlie Ridgway based on data produced by Steve Preston’s Asteroidal Occultation Predictions web site.

About Frank Taylor

Frank Taylor started the Google Earth Blog in July, 2005 shortly after Google Earth was first released. He has worked with 3D computer graphics and VR for many years and was very impressed with this exciting product. Frank completed a 5.5 year circumnavigation of the earth by sailboat in June 2015 which you can read about at Tahina Expedition, and is a licensed pilot, backpacker, diver, and photographer.


  1. Don’t suppose you’ve found any lunar and solar eclipse kml files around yet?
    With NASA’s announcements of more details about going back to the Moon yesterday, time to take Google Moon more seriously….. 😉

  2. I’ve seen some simple image overlays of solar eclipses, but I’m hoping some enterprising KML programmer will take something like Starry Night Pro (from Imaginova) and generate a database of groundtracks and make it available for Google Earth.

  3. Fred Espenak at NASA has taken this technique and posted some eclipse ground tracks in Maps but does not supply a link to the Earth points.
    I am using a program called Shadow to convert Steve Preston’t data into map points. Because Google Maps had good street level coverage only for the US, Shadow was written to only convert points over the US. There is also a problem with Google Maps’ ability – inability really – to draw lines crossing 180 degrees. After requests from Canada the Shadow cutoff was extended for me to allow me to cover all of North America and tracks extend to the east as far as they want to. But I don’t plot anything that doesn’t pass through North America, which I loosely define to include Hawaii, Bermuda, the Caribbean Islands, Central America, and Greenland. Since everything I do after creating the list of map points with Shadow is done by hand it takes a while to do a daily update when there are more than a few new or updated asteroids. I will leave other parts of the world for people living there.

  4. I suppose I should have included the URL to one of Fred’s eclipse pages in case Jim checks back.

  5. Charlie, thanks for the information. Have you done Solar and Lunar Eclipses, or just the asteroidal occultations?

  6. As far as actual observing goes I have done quite a few local eclipses and transits. I have gotten several lunar grazes in and a few full lunar occultations as well. But I have never seen an asteroidal occultation. I am a binocular and naked-eye observer and the asteroids never seem to occult anything bright enough for me to see in my light-polluted NYC skies.
    I haven’t created any eclipse maps. The program I use to convert Steve Preston’s data to a format Google can understand can’t figure out the data format of Fred Espenak’s eclipse data. I helped Fred get up to speed with the Maps API so that he could create his own eclipse maps.

  7. How exactly do you create these overlays?

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