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Allen Telescope

[Allen Telescope Dome] The Allen telescope is a 24-inch reflecting telescope of Ritchey-Chretien design, named in honour of Professor C. W. Allen, the first Perren Professor of Astronomy at University College London (1951–1972). The telescope was inaugurated by Professor D. W. N. Stibbs, Napier Professor of Astronomy at the University of St. Andrews, on 1975 May 22. It was acquired at a cost of £42,000 to replace the original 'Wilson telescope'. donated to UCL in 1925 by Mr. J. G. Wilson (the building is still referred to as 'the Wilson building').


Arc spectra for the Allen spectrograph

Built/acquired: 1974/5 Allen Telescope
Refurbished: 1991, 1998
Optics: Ritchey–Chretien Reflector
Aperture: 24" (600mm)
Effective focal Length: 265" (6742mm, f/11)
Instrumentation: Custom-built Cassegrain Spectrograph (designed by Mike Dworetsky)
Detector: Apogee Alta U47 16bit CCD, 1024x1024 array, 13x13 micron pixels
Cass plate scale: 30.6 arcsec/mm (ca. 55 arcmin f.o.v., but not used for imaging)
Drive: DC servomotors (DFM Engineering)
Mount: German Equatorial


The Allen, constructed by Ealing Beck, is operated at the Cassegrain focus (although a Coude focus is available in principle; a sketch of the optical layout is available). Many of the technical details are not well documented; although described as a 'Ritchey-Chretien' telescope, the primary mirror may be paraboloidal (not a hyperboloid, as in a true RC configuration). The primary's focal ratio is not known accurately, but is close to f/3. Total weight, including the mount, is approximately 1.5 tonnes.


Constructed in 1974, the Allen telescope's electronics and drive were replaced in a 1991 with a new computer-controlled system, designed and installed by DFM Engineering of Longmont, Colorado, USA. It was upgraded again in 1998, with a new control system, also designed and installed by DFM Engineering.