Site testing for the Discovery Channel Telescope

We present results of an extended campaign to test astronomical and environmental qualities of the intended site for the Discovery Channel Telescope, located at 2361m elevation near Happy Jack, AZ. A semi-permanent test station has been in operation since January 2003, consisting of a Differential Image Motion Measurement (DIMM) system and a weather station. Median seeing derived from DIMM measurements for January 2003 - May 2004 on 117 separate nights was 0.84 arcsec, with a first-quartile average of 0.62 arcsec. A wind sensor array deployed on a 12.2m tower is used to characterize air flow over the site. We find that ground induced turbulence becomes more prevalent below the 7.3m level. The Lowell DIMM system has also been run adjacent to the WIYN telescope for simultaneous comparative seeing measurements. Absolute correlations of DIMM seeing with WIYN image quality were good over two nights' observing under a range of environmental conditions.