urn:nasa:pds:context:telescope:keck.10m_keck1 0.0 1.7.0.0 Product_Context 2016-03-03 1.0 Initial version exported from OLAF urn:nasa:pds:context:facility:observatory.keck telescope_to_facility W.M. Keck Observatory (OLAF observatory code 378) 10 204.525284 19.825945 4160 Aerial Survey - North American (1983) Datum The 10-m Keck I Ritchey-Chretien altazimuth reflector is a 10 m telescope located at 19.825945, 204.525284 at the W.M. Keck Observatory. Instrument Host Overview ======================== The Keck I telescope began science operations in May, 1993. It was built through the W. M. Keck Foundation and is operated by the California Association for Research in Astronomy which includes the University of California, the California Institute of Technology and the National Aeronautics and Space Administration. The Keck I is located at the W. M. Keck Observatory near the summit of Mauna Kea, Hawaii. The geodetic coordinates of the telescope are: Longitude : 155d 28.4' W Latitude : +19d 49.6' N Altitude: : 4124m Mean seeing : about 0.5 arcseconds full-width-half-max in the K-band The overview and location given here are reproduced from the W. M. Keck Observatory web site, http://www2.keck.hawaii.edu/. Telescope Properties -------------------- The primary mirror comprises 36 hexagonal segments. Each segment is 1.8 meters, measured across the corners. The maximum diameter of the primary mirror is 10.5 meters, and its focal length is 17.5 meters. The telescope has 2 secondary mirrors. The f/15 secondary mirror forms a Richey Chretien system with the primary mirror. It can be used directly with an instrument mounted at the rear of the support structure for the primary mirror or with a flat tertiary mirror for a bent Cassegrain or Nasmyth focus. The f/25 secondary mirror is used with the infrared instruments at Keck I. The gold-plated mirror has a central hole to reduce the reflection of radiation to the detector from beyond the edge of the primary mirror or from the central obstruction for chop angles up to +/-150 arcseconds. A chopping mechanism resides behind this secondary mirror and does not obstruct the detector. As the chopping mechanism tilts, the image moves on the detector. This provides a way to rapidly center a target on the detector, then chop to a nearby part of sky without moving the telescope. The Keck Observatory website provides a tutorial for the chopping mechanism, http://www2.keck.hawaii.edu/inst/tools/chp/Chopping.html. The optical features of the f/15 and f/25 secondary mirror are: f/15 f/25 ----- ------ Focal length (m) : 149.6 249.7 Scale (mm/arcsec) : 0.725 1.211 Field diameter (arcmin) : 20 10 Field diameter (mm) : 870 727 Radius of curvature* (m) : 2.14 0.82 The telescope properties given here are reproduced from the Keck Telescope and Facility Instrument Guide, available at http://www2.keck.hawaii.edu/observing/kecktelgde/ktelinstupdate.pdf.