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Proceedings Paper

Wide-field aberration corrector for spherical primary mirrors
Author(s): David A. Beach
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Paper Abstract

The cost of astrographs with pupil diameters greater than 1 or 2 meters can be somewhat reduced if the primary mirror is made spherical and the aberration corrected at or near the prime focus, thus avoiding the classical Schmidt or Maksutov full pupil diameter refractive components. Such a corrector solution is presented here for large spherical primaries with speeds up to f/4. This is based on the KiwiStar principle presented here in 1997, in which a large spherical-concentric catoptric is combined by pupil transfer with a smaller spherical-concentric catadioptic to give well-corrected wide-field images of high speed and broad passband. The designs studied at the time were limited to those with entrance pupils <2m diameter, but it has been found possible to extend the aberration correction capability to pupils of larger diameter. The only significant constraint found in the present study is that the spherical aberration of primaries faster than f/4 is difficult to control. The design presented here is a 4m entrance-pupil-diameter, f/1.4 optic of 0.2 arcsec rms resolution over the whole of a 0.5° field (50mm diameter), for a bandpass of 486-850nm. To fully sample this field would require 108 pixels of 5μm dimension. An extended design with an 8m diameter primary is also shown, that may be scalable to ~30m. To achieve this performance, the strictly concentric format of the original KiwiStar design has been relaxed, thus providing extra degrees of freedom to compensate the large pupil aberrations introduced by the spherical aberration of the primary. Nevertheless, the new design still has only one relatively small and weak aspheric surface to provide zonal correction, all other surfaces being spherical.

Paper Details

Date Published: 24 October 2000
PDF: 9 pages
Proc. SPIE 4093, Current Developments in Lens Design and Optical Systems Engineering, (24 October 2000); doi: 10.1117/12.405224
Show Author Affiliations
David A. Beach, Industrial Research Ltd. (New Zealand)


Published in SPIE Proceedings Vol. 4093:
Current Developments in Lens Design and Optical Systems Engineering
Robert E. Fischer; Robert E. Fischer; R. Barry Johnson; Warren J. Smith; Warren J. Smith; William H. Swantner, Editor(s)

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