The 1.55-m Kaj Strand Astrometric Reflector

This is the largest optical telescope operated by the U.S. Navy. It was designed and built under the direction of the Scientific Director of the U.S. Naval Observatory from 1963 - 1977, Dr. Kaj Aa. Strand. It was designed to produce extremely accurate astrometric measurements in small fields, and has been used to measure parallaxes and therefore distance for faint stars. Over 1000 of the world's most accurate stellar distances and proper motions have been measured with this telescope since 1964. In recent years this telescope has also served as a test-bed for the development of state-of-the-art near-infrared detectors.

Telescope Data

• Construction
  • Optics: Corning Glass Works (blanks); Davidson Optronics (optical figuring)
  • Mounting: L&F Machine and Boller & Chivens
  • Date Completed: 1964
  • Cost: $515,400
• Optical Design: Folded Newtonian
• Effective Focal Length: 15.2-meters
• Overall Focal Ratio: f/9.8
• Focal Plane Scale: 13.5 arcsec/mm
• Primary Mirror
  • Diameter: 1.55-meters (61-inches)
  • Material: Laminated Fused Silica
  • Weight: 1350 kg (2970 lbs)
  • Figure: Paraboloid
  • Focal Ratio: f/9.8
• Secondary Mirror
  • Diameter: 0.89-meters (35-inches)
  • Material: Fused Silica
  • Weight: 190 kg (420 lbs)
  • Figure: Flat
• Total Weight (Optics, Tube and Mount): 33,000 kg (36 tons)

Instrumentation

• Pi2k - Tektronix 2048x2048 CCD Camera
• ND9 - Tektronix 2048x2048 CCD Camera with neutral density 9 apodizing spot (used for parallax measurements of bright stars measured against a faint reference frame)
• ND5 - Tektronix 2048x2048 CCD Camera with neutral density 5 apodizing spot (used for parallax measurements of bright stars measured against a faint reference frame)
• IRCAM - Rockwell 256x256 HgCdTe (NICMOS) Infrared Camera - On long-term loan to Lowell Observatory.
• ASTROCAM - SBRC 1024x1024 InSb (ALADDIN) Infrared Camera (first light August 1999)

Current Research Programs

• Stellar Parallax Program - emphasis on degenerate stars (white dwarfs - including nuclei of planetary nebulae), subdwarf stars (typically very old stars with very low metallicity), L- and T-dwarf stars ("brown dwarfs"), and bright stars against faint reference frames. Instrumentation used includes the Pi2k and ND9 CCD cameras and the ASTROCAM near-infrared camera.
• Near IR photometry of subdwarfs, L dwarfs and T dwarfs

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