Generic Misalignment Aberration Patterns in WideField Telescopes
Abstract
Axially symmetric telescopes produce wellknown Seidel offaxis thirdorder aberration patterns: coma, astigmatism, curvature of field, and distortion. When axial symmetry is broken by the small misalignments of optical elements, additional thirdorder aberration patterns arise: one each for coma, astigmatism, and curvature of field and two for distortion. Each of these misalignment patterns is characterized by an associated twodimensional vector, each of which in turn is a linear combination of the tilt and decenter vectors of the individual optical elements. For an N mirror telescope, 2(N  1) patterns must be measured to keep the telescope aligned. Alignment of the focal plane may require two additional patterns. For N = 3, as in a threemirror anastigmat, there is a twodimensional “subspace of benign misalignment” over which the misalignment patterns for thirdorder coma, astigmatism, and curvature of field are identically zero. One would need to measure at least one of the two distortion patterns to keep the telescope aligned. Alternatively, one might measure one of the fifthorder misalignment patterns, which are derived herein. But the fifthorder patterns are rather insensitive to misalignments, even with moderately wide fields, rendering them of relatively little use in telescope alignment. Another alternative would be to use telescope pointing as part of the alignment solution.
 Publication:

Publications of the Astronomical Society of the Pacific
 Pub Date:
 July 2011
 DOI:
 10.1086/661111
 arXiv:
 arXiv:1009.0708
 Bibcode:
 2011PASP..123..812S
 Keywords:

 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 50 pages, 13 figures, Accepted for Publication in PASP