Royal Astronomical Society of New Zealand


Occultations - Brian Loader


Astronomically, an occultation occurs when one body, such as the moon or a planet hides another object, often a star, by passing in front of it. A third player in the action is an observer in the right place to see or, nowadays, record the event! To make use of the occultation the observer needs to make, among other things, an accurate timing of when the star disappears behind the moon or planet and/or when it reappears again.

The use of the times of occultations has varied over the ages. Some of these uses will be covered in later articles. Originally they were observed visually using an accurate time piece referenced to an accurate time source. All this has changed in the 21st century with the use of video and GPS sourced times giving a much more reliable and certainty of the event and its time. This has resulted in a widening of the use of occultation observations and in their application to other fields. Even to playing a minor part in the Kepler mission’s aim of discovering planets orbiting other stars. Much software has been developed to assist in observing and analysing the results of occultation observations ... available free.

All this and more will be covered in later articles. For now we’ll have a look at just what occultations are.