The 2.5 m telescope of the Sloan Digital Sky Survey

James E. Gunn, Walter A. Siegmund, Edward J. Mannery, Russell E. Owen, Charles L. Hull, R. French Leger, Larry N. Carey, Gillian R. Knapp, Donald G. York, William N. Boroski, Stephen M. Kent, Robert H. Lupton, Constance M. Rockosi, Michael L. Evans, Patrick Waddell, John E. Anderson, James Annis, John C. Barentine, Larry M. Bartoszek, Steven BastianStephen B. Bracker, Howard J. Brewington, Charles I. Briegel, Jon Brinkmann, Yorke J. Brown, Michael A. Carr, Paul C. Czarapata, Craig C. Drennan, Thomas Dombeck, Glenn R. Federwitz, Bruce A. Gillespie, Carlos Gonzales, Sten U. Hansen, Michael Harvanek, Jeffrey Hayes, Wendell Jordan, Ellyne Kinney, Mark Klaene, S. J. Kleinman, Richard G. Kron, Jurek Kresinski, Glenn Lee, Siriluk Limmongkol, Carl W. Lindenmeyer, Daniel C. Long, Craig L. Loomis, Peregrine M. McGehee, Paul M. Mantsch, Eric H. Neilsen, Richard M. Neswold, Peter R. Newman, Atsuko Nitta, John Peoples, Jeffrey R. Pier, Peter S. Prieto, Angela Prosapio, Claudio Rivetta, Donald P. Schneider, Stephanie Snedden, Shu I. Wang

Research output: Contribution to journalArticlepeer-review

1873 Scopus citations


We describe the design, construction, and performance of the Sloan Digital Sky Survey telescope located at Apache Point Observatory. The telescope is a modified two-corrector Ritchey-Chrétien design with a 2.5 m, f/2.25 primary, a 1.08 m secondary, a Gascoigne astigmatism corrector, and one of a pair of interchangeable highly aspheric correctors near the focal plane, one for imaging and the other for spectroscopy. The final focal ratio is f/5. The telescope is instrumented by a wide-area, multiband CCD camera and a pair of fiber-fed double spectrographs. Novel features of the telescope include the following: (1) A 3° diameter (0.65 m) focal plane that has excellent image quality and small geometric distortions over a wide wavelength range (3000-10,600 Å) in the imaging mode, and good image quality combined with very small lateral and longitudinal color errors in the spectroscopic mode. The unusual requirement of very low distortion is set by the demands of time-delay-and-integrate (TDI) imaging. (2) Very high precision motion to support open-loop TDI observations. (3) A unique wind baffle/enclosure construction to maximize image quality and minimize construction costs. The telescope had first light in 1998 May and began regular survey operations in 2000.

Original languageEnglish (US)
Pages (from-to)2332-2359
Number of pages28
JournalAstronomical Journal
Issue number4
StatePublished - Apr 2006

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Surveys
  • Telescopes


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