Abstract
The photoelectric astrolabe type I was made in China in 1971 [2]; and several| improved photoelectric astrolabes, of a second model, were constructed from 1972 to 1974. The principles and a description of the main parts of the new instruments are as follows: 1. (1) By means of a fused quartz mirror system and mercury horizon (shown in fig. 4), a telescope with a fixed glass grid, three photomultipliers with respective a. c. amplifiers and a time recorder, the astrolabe can determine the time of almucantar transit of a star without personal error. 2. (2) The evacuated Ritchey-Chrétien telescope has an aperture of 20 cm and a focal length of 2.4 m. 3. (3) As is expected, the vacuum telescope tube with horizintal entrance window is able to eliminate astronomical refraction, the dependence of refraction on the spectral class of the star and irregular refraction in the tube. Besides, the vacuum tube provides a stable environment for optical system, especially for mercury horizon. 4. (4) The astrolabe is equipped with high and low speed motors, as well as an automatic tracking mechanism in azimuth direction. 5. (5) In order to reduce the heat influence from the surroundings, the astrolabe is set on the first floor of the observing building, whereas the control console, electronic equipments and the operator are on the ground floor. 6. At Shanghai Observatory, observations have been carried out with the new instrument since Sep. 1974. The excellent results obtained will be published later on.
Published Version
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