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Light Scattered from Polished Optical Surfaces: Wings of the Point Spread FunctionRandom figure errors from the polishing process plus particles on the main mirrors in a telescope cause an extended point spread function (PSF) declining approximately as the inverse square of the sine of the angle from a star from about 100 micro-rad to a right angle. The decline in at least one case, and probably in general, proceeds as the inverse cube at smaller angles where the usual focal plane aperture radius is chosen. The photometric error due to misalignment by one Airy ring spacing with an aperture of n rings depends on the net variance in the figure. It is approximately 60/(n+1)(3) when using the data of Kormendy (1973). A typical value is 6 x 10 to the -5th power per ring of misalignment with n = 100 rings. The encircled power may be modulated on a time scale of hours by parts per thousand in a wavelength dependent manner due to relative humidity effects on mirror dust. The scattering according to an inverse power law is due to a random walk in aberration height caused by a multitude of facets and slope errors left by the polishing process. A deviation from such a law at grazing emergence may permit monitoring the dust effects.
Document ID
Document Type
Conference Paper
Kenknight, C. E.
(Arizona Univ. Tucson, AZ, United States)
Date Acquired
August 12, 2013
Publication Date
November 1, 1984
Publication Information
Publication: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry
Subject Category
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.
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