required) announced the discovery by Grzegorz Pojmanski (Warsaw
University Astronomical Observatory) of C/2006 A1 from images taken
for the All Sky Automated Survey at Las Campanas taken on 2006 Jan.
1 and 4. At that time the comet was estimated to be 1' diameter,
from the relatively small scale (15" per pixel) CCD survey
images taken with a 180-mm-focal-length f/2.8 telephoto lens.
Pojmanski soon afterwards identified pre-discovery images from
2005 Dec 29 and the comet was also located on SWAN/SOHO images in
the ultraviolet back to 2005 Dec 25.
At discovery it was in the far south of the sky at declination
-68°, approaching Sun and Earth, but already less than 60°
apparent elongation from the Sun. Perihelion was due on 2006 Feb 22
at a distance of 0.56 AU but still south of the equator and close to
the Sun in the sky.
By the time the image was obtained (above) the comet was moving
rapidly north, still only 0.60 AU from the Sun, at an elongation of
37° and was at the closest point it would come to Earth, at a
distance of 0.77 AU.