2014 programme

Sun 14:00-14:30

Observing Occultations Using Video: A Beginner’s Guide

Jacquie Milner

Astronomical Society of WA, Perth Observatory Volunteer Group

An occultation is when one body covers or ‘hides’ another. Asteroids, planets and moons can occult stars, the Moon and occult the planets and even solar and lunar eclipses are occultation events as well. These events can tell us much more than how big or what shape an asteroid is or, in the case of lunar occultations, how well we know the orbit of the Moon. They can help to refine the orbit of an asteroid; if it has a satellite or is a double asteroid; if the position of the star it occulted was known accurately and they regularly result in the discovery of new double stars. Occultations involving Pluto are particularly valuable at the moment as the New Horizons spacecraft approaches the distant dwarf planet, monitoring the state of Pluto’s atmosphere and even keeping a check on where Pluto actually is!

The first occultation observers did their work with time beeps from short-wave radios and tape recorders. Now there are integrating video cameras allowing observers to push beyond the visual limits of their telescopes and video time inserters allowing timings to be made with millisecond precision. The video occultation manual “Observing Occultations Using Video: A Beginner’s Guide”, aims to help interested observers understand where to look at the right time, what equipment is needed and how to report their results after the observation has been made. Even experienced observers will find this document useful for improving the quality of their observations and their accuracy.