This is a CCD image of comet 1993a "Mueller", taken on October 6, 1993, using
SBIG's ST-6 CCD-camera and a 288mm f/5.2 Schmidt-Cassegrain telescope.The
exposure lasted from 19:11 U.T. to 19:21 U.T.
The field of view is 19.6' x 14.4'. The comet has a coma diameter of some-
what more than 3' and a fan-shaped tail, up to 7' long, between P.A. 220o
and P.A. 310o. (Sorry, I mixed that up in my posting last week: 1993a has
a fan-shaped tail oriented around P.A. 270o, while 1993p shows a slender
AN-tail pointing nearly exactly northward. However, this an-tail may not be
visible any longer...)

The brightest star visible (PPM 7788) is of photographic magnitude 8.8. In
this GIF-image, this star and the head of the comet appear to be nearly of
the same brightness. However, a close inspection of the original CCD-image
(which has a resolution of 16 bit per pixel rather than 8 bit for GIFs)
shows that the star trail is satured at a value of 65535, while the brightest
pixel in the comet's head reaches a value of only 15608. According to our
measurements, the comet is of mag 10.5 in red light (where unfiltered, thick
CCD's are most sensitive).Keep in mind that a comet has usually bright
emissions in blue and green light, where our CCD is not that sensitive.