coleostat

photographic device

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Last updated

June 24, 2026

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A coelostat is a device with a motor-driven, flat mirror that continuously reflects a portion of the sky into a stationary telescope. The mirror rotates on an axis pointing to a celestial pole, completing one revolution every 48 hours, which keeps the telescope's image steady and non-rotating. This is especially useful for eclipse observations where complex telescope mounts are impractical. Other similar instruments include the heliostat, which focuses sunlight into a telescope, and the siderostat, used for observing stars. The coelostat was invented by Gabriel Lippmann in 1895.1

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Gabriel Lippmann
He also invented the coleostat, an instrument that allowed for long-exposure photographs of the sky by compensating for the Earth’s motion during the exposure.
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He also invented the coleostat, an instrument that allowed for long-exposure photographs of the sky by compensating for the Earth’s motion during the exposure.
Read More