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ostruve 03

See movie 


Prime focus: f/3.9

ProEM (pending)

Cassegrain focus: f/13.7

ProEM (active)

SQUEAN (active)

Sandiford Echelle Spectrometer (SES) (inactive)

Cassegrain Spectrometer (ES2) (inactive)

CCD WHT Camera - Cassegrain f/13.7 focus (inactive)



Primary mirror
Diameter 2.08 m (82")
Focal length 8.13 m (26.7')
F-ratio 3.9
Field angle 63.5 arcmin
Plate scale 25.4 arcsec/mm
Cassegrain focus
Focal length 28.53 m (96.6')
F-ratio 13.7
Field angle 20 arcmin
Plate scale 7.23 arcsec/mm
Coudé focus - decommissioned
Focal length 47.70 m (156.5')
F-ratio 22.9
Plate scale 4.3 arcsec/mm


Primary mirror
Weight 1900 kg (4200 lbs)
Thickness 29.8 cm (11.75")
Material Borosilicate glass (Pyrex™)
Diameter 2.64 m (8'8")
Length 8.2 m (27')

41 t (45 tons)

Polar axis SKF ball radial thrust bearings
Dec axis Tapered roller bearings
Diameter 19 m (62')
Weight 104 t (115 tons)


Started 1933
Completed 1939
Design Otto Struve
Telescope Warner and Swasey Co.
Dome Patterson Leitch Co.
Optics C. Lundin

Control Systems

• Remote observing capability.
• Safe automation to target.
• Actual on-sky rms tracking noise of 0.1 arcsec relative to the commanded rate.
• Autoguiding tuned to OST's step response function, and guider specialized for calculating the PSF on a slit.
• Dome automation during tracking.
• Ephemeral tracking using JPL Horizons data. Check out OST tracking Soviet spy satellite Molniya 1-52 in the movie link above!
• Computer control of dome slit, mirror cover, and baffle tube. Wide-field surveillance cameras on dome and tube.