A Photoelectric Area Scanner.
K. D. Rakos · The Astronomical Journal · 1965
This new astronomical instrument is designed primarily to measure magnitude differences of very close double stars, or of a planet and its satellite. The fundamental principle is based on a linear scanning technique, the use of a narrow slit and a data presentation system which includes a linear digital output in addition to photographic recording witli an oscilloscope. As the instrument was recently tested on the' Navy's new 61-in. telescope, the slit was 0'?6 wide and 6'?5 long. The area exposed to the sky was therefore about 4 sq sec of arc in area. In ordinary photoelectric work it is rarely possible (even under ideal conditions) for an observer to use less than a 10" aperture or about 80 sq sec of arc. The large "off" time during each scan is more than compensated by the fact that accurate photoelectric photometry can be performed on very closely separated objects such as double stars which have heretofore been entirely beyond the reach of photoelectric photometers. Preliminary tests under poorer-than-average seeing conditions show stars 3'!5 apart to be clearly separated. An eclipse of Phobos when only 5" from Mars has been observed when the brightness ratio was. more than 10~. The h~itiaI development and subsequent tests of this equipment were made possible by a NASA grant to the Lowell Observatory.