Timing-system design considerations for a mobile astrolabe

The Danjon Astrolabe at the Naval Observatory has been traditionally used to determine Universal Time and improve the systematic accuracy of star positions. During the past year, it has been used to determine latitudes and longitude at remotely scattered sites for geodetic purposes. Operating this instrument away from the Observatory necessitated a mobile support and timing system rugged enough to operate dependably in ever changing, and somtimes harsh, environmental conditions. This paper describes the performance of the astrolabe timing system, gives the basic engineering design considerations, and describes the equipment and instrumentation.