In the atmospheric boundary layer near the surface, meteorological quantities such as the gradients of temperature in time and space and turbulence parameters are directly related to telescope design and construction specifications. Also, since atmospheric boundary layer conditions may vary significantly over short distances where the topography is complex, an objective evaluation and comparison of candidate sites for SALT within the area of Sutherland Observatory is warranted. The study was conducted in two parts. A 10m-high meteorological mast was equipped to measure wind speed, wind direction, temperature and relative humidity. The purpose of these observations was to obtain contemporaneous measurements of the seeing at the reference site and each of the candidate sites so that an objective ranking of candidate site quality could be made.
Heights are in metres.
Selected Results Table 2. As determined from DIMM measurements over the period April 1994 - February 1998. When seeing values are weighted according to the observed frequency of wind directions, the median difference is 0.18 arcsecond. For example, when imaging point-like sources, the observing efficiency is proportional to the inverse square of the seeing. These findings indicate that the potential for improving seeing by elevating the telescope is large in the first 5m, significant in the next 10m but that raising the telescope to heights above 15m will not improve the seeing quality.