S&T: Dennis di Cicco

The Moon, in its monthly travels around the sky, often passes in front of moderately bright stars. These lunar occultations are fascinating to watch in a telescope. (See Occultations: The Fastest Things in the Sky, by Alan MacRobert.) Occultations by asteroids, where a star is blotted out momentarily, can be even more exciting.

Amateurs interested in timing these occultations can make real contributions to science. (See How and Why to Make Occultation Timings.) But first you have to know what occultations will occur in your area.


You can find many occultation predictions at the International Occultation Timing Association’s site, www.lunar-occultations.com/iota. There you can also download the free Occult program to create full, detailed predictions for your exact location.

Grazing-occultation maps

Go to iota.jhuapl.edu/grazemap.htm. Detailed interactive maps of some of the better North American graze paths are at Brad Timerson’s site, www.timerson.net/IOTA.

Asteroid occultations

The main page (with links to predictions, observing methods, reporting, and past results) is at www.asteroidoccultation.com/observations.

Timing methods

Go to iota.jhuapl.edu/timng920.htm.

Online book

Lots about observing occultations of every type is in Chasing the Shadow: The IOTA Occultation Observer’s Manual, available free at www.poyntsource.com/IOTAmanual/Preview.htm.


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