Star pair

The term star pair means in astrometry and geodetic astronomy a combined measurement of two stars in certain directions or zenith angles . It is used to increase the measurement accuracy or to reduce instrumental errors .

Important uses are

• In some methods of determining latitude, the combination of stars that pass the meridian at a distance of a few minutes at almost the same zenith distance, but through the north and south branches of the meridian;
  • see also Horrebow-Talcott method and Sterneck method ;
  • for azimuth measurement according to the Embacher method with two stars in east and west largest digression ;
• when determining the time with stars in the first vertical (in the east or west);
• when determining locations with the astrolabe , in which successive stars are approximately opposite.

There are two other uses of the word 'star pair' in common parlance :

• two stars that appear adjacent to the naked eye - e.g. B. the two main stars in the winter constellation of Gemini or in the southern sky α and β Centauri ,
• technically incorrect a double star (ie two suns circling each other).