Astrometry with small telescopes

Abstract

At the Quonochontaug Observatory of the University of Rhode Island, we specialize in the development of simple seeing limited optical telescopes. Our main instrument is a heavy Serrier trussed f/10.7, .4-m astrometric reflector which provided the last-minute astrometry in the successful prediction of the occultation of SAO 120774 by Herculina in 1978. It is similar in design to the U. S. Naval Observatory 1.5-m reflector. Its scale of 47.1“/mm makes it potentially more powerful than the Lick .5-m, f/7 astrograph. However, its field of view of 1.3° × 1.7° is insufficient to capture enough AGK3R reference stars which are needed to consistently provide tenth-of-a-second-of-arc accuracy. To solve this problem, a .24-.32-m, f/6.3 lensless Schmidt was developed to provide a 3.8° field at 135”/mm and is mounted on the .4-m telescope. It can be used by itself and/or to provide a secondary reference frame for the main instrument. The measures from the plates and film are reduced by a suite of interactive computer programs which allows one to choose the proper reduction model based on the Eichhorn criterion. Over 100 positions of stars, asteroids, comets and supernovae have been provided with these instruments, and a regular observing program including participation in the IHW is underway.