Very-wide-angle optical systems suitable for spaceborne photometric measurements

摘要

Spaceborne visible-light images for observing the large angular extent of the solar corona require 0.1% differential broadband photometry over similar to 1 degrees sky bins. When we are using a CCD camera, this specification requires spreading unresolved images over many pixels. Large images ease correction for aberration or field curvature. Permitting large images allows simple and lightweight very-wide-angle designs employing spherical and toroidal mirrors and thick lenses that can view almost the entire sky. We present formulas and graphic results relating sky angle to focal-plane position and determining the tangential and sagittal focal surfaces governing image size at the CCD. Laboratory measurements with two prototype configurations confirm the calculations. (C) 1998 Optical Society of America. [References: 26]