The accuracy requirements for pointing a ground-based telescope or antenna are comparatively modest; the latest Earth orientation models used by specialists have precision goals measured in microarcseconds and are excessive for such humble applications. Abridged formulations offer an attractive alternative: easier to get right, and much quicker to compute. Moreover, the revised computational procedures that the IAU introduced in 2000 to assist high-precision studies of Earth rotation lend themselves to approximation. Together with basic models for aberration and refraction, a page of inline C code is enough to predict the observed altazimuth coordinates of a star to an accuracy of 1-2 arcseconds, which is adequate for pointing a small telescope. This can be complemented by a similarly concise formulation of the basic pointing corrections for an equatorial or altazimuth mount.

Date Published: 14 July 2008
PDF: 12 pages
Proc. SPIE 7019, Advanced Software and Control for Astronomy II, 701908 (14 July 2008); doi: 10.1117/12.788712

Published in SPIE Proceedings Vol. 7019:
Advanced Software and Control for Astronomy II
Alan Bridger; Nicole M. Radziwill, Editor(s)