W.M. KECK OBSERVATORY 10-M KECK I       
        RITCHEY-CHRETIEN ALTAZIMUTH REFLECTOR
=============================================

  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.        
                                                                              
        GROUP                        = OBSERVATORY_PARAMETERS                 
          OBSERVATORY_ID             = 'OBS378'                               
          NAME                       = 'W.M. KECK OBSERVATORY'                
          COUNTRY                    = 'USA'                                  
          ADDRESS                    = 'CALIFORNIA ASSOCIATION FOR            
  RESEARCH IN ASTRONOMY\N                                                     
                                        P.O. BOX 220\N                        
                                        KAMUELA, HAWAII'                      
        END_GROUP                    = OBSERVATORY_PARAMETERS                 
                                                                              
        GROUP                        = TELESCOPE_PARAMETERS                   
          TELESCOPE_ID               = 'T1'                                   
          NAME                       = '10-M KECK I RITCHEY-CHRETIEN          
  ALTAZIMUTH REFLECTOR'                                                       
          APERTURE                   = 10 <METERS>                            
          LONGITUDE                  = -154.525284 /* -154 31 31.02 */        
          LATITUDE                   =   19.825945 /* +19 49 33.4 */          
          ALTITUDE                   = 4160 <METERS>                          
          COORDINATE_SOURCE          = 'Aerial survey - North American        
  (1983) datum'                                                               
        END_GROUP                    = TELESCOPE_PARAMETERS