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Evaluation of image quality in a Cassegrain-type telescope with an oscillating secondary mirrorA ray-trace analysis is described of aberrations and extreme rays of a Cassegrain-type telescope with a tilted secondary mirror. The work was motivated by the need to understand the factors limiting image quality and to assist in the design of secondary mirrors for three telescopes with oscillating secondary mirrors (OSM) used at Ames Research Center for high altitude infrared astronomy. The telescopes are a 31-cm-diameter Dall-Kirkham (elliptical primary, spherical secondary) flown aboard a Lear jet, a 71-cm balloon-borne Dall-Kirkham flown on the AIROscope gondola, and a 91-cm true Cassegrain (parabolic primary, hyperbolic secondary) flown aboard a C-141 jet transport. The optics for these telescopes were not designed specifically for OSM operation, but all have OSM's and all must be used with various detector configurations; therefore, a facility that evaluates the performance of a telescope for a given configuration is useful. The analytical expressions are summarized and results for the above systems are discussed. Details of the calculation and a discussion of the computer program are given in the appendices.
Document ID
Document Type
Technical Memorandum (TM)
Erickson, E. F.
(NASA Ames Research Center Moffett Field, CA, United States)
Matthews, S.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 3, 2013
Publication Date
February 1, 1975
Subject Category
Instrumentation And Photography
Report/Patent Number
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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