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High-Resolution Telescopes

NSSDC ID: 1968-110A-01
Mission Name: OAO 2
Principal Investigator: Prof. Fred L. Whipple


This Smithsonian Astrophysical Observatory (SAO) experiment, referred to as the Celescope experiment, consisted of two major subassemblies: an optical package, containing four 12-in. Schwarzschild telescopes that used Uvicons to produce television pictures of star fields, and an electronics package. The purpose of Celescope was to measure the UV brightness of a large number of stars. The Uvicons were fitted with filters constructed by combining halves of filter blanks. Redundant data were obtained, thereby, over four different passbands. These passbands were from 1200 to 1500 A, 1375 to 1800 A, 1800 to 2800 A, and 2850 to 3250 A. When struck by UV radiation in the wavelength range to which it was sensitive, the photocathode of a Uvicon emitted electrons in proportion to the intensity of the radiation. The electrons were accelerated and electrostatically focused onto a target, forming a pattern that was half the size of the initial optical image at the focal plane. A time exposure could be made by allowing the electron "picture" to build up on the target. Operated by ground control, time exposures of up to 30-s duration could be made of a field 3 deg square. The optical parts of Celescope weighed 440 pounds, and its electronics 77. The only significant failure during the 16 months of operation was caused by overexposing one of the Uvicons to sunlight. The sensitivity of the other Uvicons decreased significantly but in a correctable manner, although this decrease was the primary reason that the operation of this experiment ceased in April 1970. Over 8500 2-deg by 2-deg star fields were observed, covering about 10% of the sky and yielding observations of some 5000 objects. For more details, see R. N. Watts, Jr., Sky & Tel., p. 280, May 1969; W. A. Deutschman, Pub. Astron. Soc. Pac., v. 84, p. 123, 1972.

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Astronomy: Ultraviolet

Additional Information

Questions or comments about this experiment can be directed to: Coordinated Request and User Support Office.



NameRoleOriginal AffiliationE-mail
Mr. John F. McNallOther InvestigatorUniversity of Wisconsin-Madison 
Prof. Fred L. WhipplePrincipal InvestigatorSmithsonian Astrophysical
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