The Comparison of the Observations Made with the Vacuum Tube of A Photoelectric Astrolabe of Type Ⅱ with Those Made with the Nonvacuum Tube

The 57 groups of observations obtained with the unvacuum tube of a plioto-dcctric astrolabe of Type Ⅱ are compared with the data obtained with the vacuum tube of the photoclectronic astrolabe of Type Ⅱ.The preliminary results show that the error of observing a single star with the vacuum tube is 0."03 smaller than that with the unvacuum tube.The influence of the anomalous refraction within the tube needs to be corrected in a proper mode.