Radcliffe 74-inch (1.9 m)
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Index: Summary; History; Current; Technical; Source
In brief
Important Contributions:
Description:
- Largest
telescope in South Africa from 1951 - 2004 until the S.A.L.T.
telescope
came into use.
- The contract was signed with Grubb Parsons for the building of the telescope in August 1935. Due to problems in casting such a large mirror, the third attempt was successful in 1938. World War Two delayed all attempts to complete the mirror and work only resumed in 1945. The mirror reached Pretoria only in 1948.
- The
primary mirror was slightly thinner than anticipated and a modification
had to be made to the main cell of the telescope in order to
fit the mirror safely. David
Evans
was tasked with this modification. [Evans Obituary – MNASSA,
p.6]
- Although the telescope was designed as a Cassegrain, for the first two years photography was confined to the secondary mirror in a Newtonian configuration. [Evans Obituary – MNASSA, p.6]
- Due
to light pollution problems at Radcliffe Observatory, and with
the amalgamation of astronomical facilities at the time (S.A.A.O.),
the telescope was moved in 1974 to Sutherland.
Historical Background
Owners:
Where located:
- Radcliffe Observatory 1948 - 1974
- Sutherland 1974 - present
Current Information
Present Location:
Sutherland
Owner:
S.A.A.O.
Status:
Condition:
Technical Details
Type:-Reflector with choice of Newtonian focus, or as a Cassegrain of Coude for spectroscopic work.
Aperture: 74 inch (187.9 cm)
Focal Length:
Mirror:
Primary mirror:
- Made by Corning Glass Company of New York [Moore, p.115]
- Disk made out of Pyrex, at a weight of 3.6 ton. (Telescope structure containing mirror weighs 5 ton) [Moore, p.115; p.117.]
- In 1935 the order for the mirror was placed. The first two casts of mirror were unsuccessful. The third cast was successful and the mirror reached Grubb Parsons in Newcastle by October 1938. The Second World War interrupted the grounding, polishing and testing of the mirror [Moore, p.115]
- The third cast mirror was slightly thinner than anticipated and a special modification had to be made to the telescope housing in order to fit the mirror securely. [Evans Obituary – MNASSA, p.6]
Mounting: "the planner, had little faith in the constancy of the local electricity supply and the drive mechanism of the telescope was actually regulated by a tuning-fork!" [Copied from Moore, p.117.]
Attachments:
-
Evans
Spectrograph.
David
Evans
designed and built a Newtonian spectrograph. (a large spectrograph)
[Smits; Evans Obituary – MNASSA, p.7]
- Coude Spectograph 1960 [Smits]
Manufacturer: Grubb Parsons of Newcastle Ireland
Building:
- Radcliffe. (Pretoria) Part of the agreement with Grubb Parsons telescope makers was to build both the telescope and the building to house the telescope. The building had a 61-ft (18.5 m) turret. The "unusually shaped turret" was double walled for temperature control. The outer cover was made of galvanised steel and the inner wall of wood fibreboard. The non-rotating part of the building was made of an inner brick wall surrounded be an outer sheath of metal lathing (forming a cavity), coated with rough cast plaster. [Moore, p.115; p117]
Picture: Moore, P. & Collins, P., Astronomy in Southern Africa, p.117; p.118.
- Sutherland.
Sources
Link
to the Main Bibliography
Section
and more information about Sources.
Documentation:
Pictorial Sources:
Bibliography:
- Evans Obituary: MNASSA Vol. 64, Nos 1 & 2, February 2005.
- Moore, P. & Collins, P., Astronomy in Southern Africa, p.115; pp.117 - 119. (General Source)
- Smits, P., A Brief History of Astronomy in Southern Africa. (Unpublished
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