An Automatic Scanning and Recording Photometer for Night Sky Studies

This paper describes a photoelectric photometer which scans the entire sky in 32 minutes, recording the light energy in a 100A band as a function of altitude and azimuth. The light is chopped by a rotating shutter and detected by a photo-multiplier tube, the output from which is amplified and synchronously rectified to produce a d.c. signal for the graphic recorder. Three different types of automatic scanning are provided, as well as a manual control of the various functions. The minimum energy which may be reliably recorded, using a 4-inch, f:1 lens, is of the order of 10−13 watt.