Equatorial (telescope)
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An equatorial is a late 19th century measuring instrument for the precise determination of asterisks .
It is an equatorially mounted, long focal length telescope with large, finely divided circles and reading microscopes. In contrast to the meridian circle , you can also measure direct right ascension and declination differences outside the meridian .
The largest telescope of this type ever built is in Hamburg-Bergedorf (30 cm aperture , 3 m focal length ). This observatory has made a special contribution to positional astronomy and star catalogs such as the AGK3 since around 1900 . About 20 years earlier, Maurice Loewy had built a special equatorial with a Coudé beam path and a particularly long focal length for his photographic lunar atlas at the Paris observatory .
The theory of this measurement method comes from the Gotha astronomer Hansen , who had such a device built for the Gotha observatory in 1860 at the Repsold company in Hamburg . This equatorial did not require any tracking, since the measurement is made directly at the star passage on the thread network. For this, however, finely divided circles as large as possible are necessary. Because the instrument did not meet expectations to the extent desired, it was dismantled again in 1885 for normal tracking following the apparent rotation of the sky .