SEEING MEASUREMENTS AT FREELING-HEIGHTS AND SIDING-SPRING-OBSERVATORY

A low-cost differential image motion monitor (DIMM), consisting of an Ii-inch Celestron, an SBIG ST-4 autoguiding CCD camera and a PC, is de scribed. Two such systems were used during June-July and November-Dece mber 1993 to make near-simultaneous seeing measurements at Freeling He ights in the Northern Flinders Ranges and at Siding Spring Observatory . The results of these campaigns show that the seeing distribution is generally similar at both sites, with the most common seeing Value bei ng similar to 1.2 ''. Siding Spring does, however, have slightly more bad seeing (>2 '') than Freeling Heights. Weather records from Arkaroo la Resort (15 km south of Freeling Heights) indicate that there is sim ilar to 15% less cloud cover at Freeling Heights than at Siding Spring . Episodes of rapid seeing deterioration at Siding Spring in winter ar e shown to coincide with warm air masses crossing the mountain.