An inexpensive sidereal drive unit for 1-m class astronomical telescopes

Abstract

We describe here the details of the concept, the construction, and the performance of an accurate and inexpensive sidereal tracking drive unit (SDU) for the l-m or larger class of astronomical telescopes. The SDU is tunable and has a very highly stable and undistorted sinusoidal wave shape. The SDU consists mainly of a variable drift-free drive rate generator and a distortion-free, low-cost power amplifier. Tracking accuracies of less than a couple of arcseconds in sky are achieved in 60 min of observation time. The unit can also be used in negative feed back mode to correct any errors in the tracking system. The accuracies in frequency stability obtainable with the SDU and the feasibility of operation in negative feedback mode for correcting tracking errors are not possible in the commercially available battery back-up uninterrupted power supply (UPS) units. The total cost of the SDU currently works out to be approximately $200 (US) and requires about one man-month for building and testing.