All Sky Automated Survey - Camera Lens
The Prototype Instrument of the All Sky Automated Survey is equipped
with the Sigmatel 135mm f/1.8 telephoto lens.
Overall condition of the lens is good (even though it was second-hand
purchase), but its optics is not the best:
Point Spread Function (PSF) is "triangular" rather than axi-symmetric, with
two unpleasant "fingers": 
Full Width Half Maximum (FWHM) of the PSF profile is about 2.5 pixels
(30 arcsec) at the best focus, so we don't need to de-focus instrument to get
proper sampling of the star images.
Fortunately PSF is constant over the whole 3 deg x 2 deg field of view.
Grzegorz Pojmanski /
gp@sirius.astrouw.edu.pl