Jones, H. Spencer (Harold Spencer), 1890- · London E. Arnold & co. · leaf 197
Fig. 57.—Various Methods of using a Reflecting Telescope to give difierenteqviivalent Focal Lengths. reflector, without secondary magnification, the focal length ofthe telescope is also 25 feet (Pig. 57[a]). In order to use it asa Cassegrain reflector, the upper section of the telescope…
Astronomy
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