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Star Filters

A photometric system for classifying stars, first formulated by Vilnius Observatory of Lithuania, is currently being calibrated for the southern hemisphere sky by astronomers at Carter Observatory and Victoria University.

Photometric systems consist of a variety of glass filters used to select different wavelengths of light for subsequent measurement by a telescope. The Vilnius system has seven filters ranging from the ultraviolet to the near infrared, carefully chosen to provide information about a star's surface composition, temperature and brightness. The advantage of this filter system over others is that it allows better corrections for the light absorbed by interstellar gas and dust clouds, and the Earth's atmosphere, along the observer's line of sight to the star.

Previously these filters were only obtainable from Vilnius University. However, a "prescription" for the filters, using more commonly available types of glass, will be published soon, which should increase the system's popularity amongst astronomers. This, together with a set of calibrated measurements of southern stars to complement the 5000 northern stars observed by the system, will allow more accurate astronomical measurements to be made in the future,

Murray Forbes, Victoria University.