Heliometer

Instrument for measuring distances between neighboring stars. It consists of a telescope with the object gla sawed in two along a diameter so arranged that the two IMG:content-0537.jpg:[graphic] IMG:content-0538.png:[graphic][merged small] halves can slide by each other. The amount of displacement is shown by a scale. The distance between two stars viewed through the two halves of the object gla respectively is given very accurately by this scale.