Improvements to the Optics of the Whipple 10 m Telescope

The Whipple 10 m reflector was built in 1968 and designed to make high energy gamma-ray observations with light detectors of 1 degree diameter. The current Whipple camera has pixels of 0.12 degree diameter; ideally the point spread function (PSF) of the reflector should have a FWHM less than this. Measurements of the PSF indicated a width of 0.18 degree above elevations of 60 degree where most observations are made. A study of the optical properties of the reflector showed two causes of light spreading: gross deflection of the optical support structure and individual facet motion. These effects can be lessened by bias alignment, i.e., misalignment of the facets in the horizontal position where the alignment is performed, to give an optimized image over the operating range of elevation. The results of the bias alignment and their effect on the gamma-ray detection efficiency will be presented.