Occultations and Transits Special Interest Group

revised 2004 Jan 16

About this SIG

The AAAP Occultations and Transits Special Interest Group (OTSIG) is a special section of the club devoted to observers who enjoy observing the occultations by the Moon, asteroids, and other bodies in the solar system, as well as transits by the moons of Jupiter and planets across the Sun.


John Holtz
phone: 724-352-7596
Email: JWHoltz@aol.com


For timely updates pertaining to occultations visible from the Pittsburgh area, such as observing sites and rendezvous instructions for grazing occultations, finder charts for upcoming asteroidal occultations, or meeting dates for this Special Interest Group, please visit John Holtz' Occultation Updates page.

Background on Occultations

Occultation: the obscuration of one celestial body by another of greater apparent diameter, especially the passage of the Moon in front of a star or planet. -- Astronomical Almanac.

In plain English, one object completely covers another! -- John Holtz.

There are four primary types of occultations that the Occultations & Transits Special Interest Group (OTSIG) will focus on.

Occultation Timings

Lunar and asteroidal occultations can provide valuable scientific data, provided the following information is recorded:

  1. The time of the event, to the nearest fraction of a second. This is typically achieved by using a short wave radio to receive time signals while recording the event verbally with a tape recorder. Alternatively, a video camera held to the eyepiece can be used to record the event. Sensitive video cameras can obtain timings to an accuracy of 1/30 second, where as visual timings are generally accurate to only 0.2 seconds at best.
  2. The observer's position, to within 100 feet. This can be obtained by measuring your location relative to a landmark on a 1:24,000 topographic map, or by averaging the position reported by a GPS receiver for a several minute period.


Background on Transits

A transit occurs when a smaller object passes directly in front of the larger object: the opposite of an occultation. There are two types of transits that the OTSIG will focus on:


Occultations and Transits SIG pages
Home | Total | Grazing | Asteroidal | Jupiter's Moons | Planetary Transits