|Being the middle of summer the ambient temperature didn't allow the
CCD to cool down to -40°C (the temperature it is normally operated at) and imaging started
at 22:00 UT with the CCD at -33.3°C.
there was potentially a large area to search the camera was binned 2x2, cutting the image download time by a factor of four and allowing
two 13 second exposures to be taken per minute. With a field of 25x25
arcmin the search was conducted in 20x20 arcmin squares, giving some overlap to help
counteract the effects of vignetting. For convenience the grid for the uncertainty map
above was set to match the search field size.
6 images of each search area were taken before moving to the
next area (sometimes the magnitude given on the NEOCP can be
significantly brighter than an object really is, so 6 images
allows detection even if the object turned out to be fainter than the indicated 17th
The first set of 6 images was taken centred on the nominal ephemeris position.
The next run was chosen to be centred on the adjacent part of the uncertainty map to
the SouthWest, re-centering 10 arcmin South and 10 arcmin West,to align
with the 20 arcmin squares on the grid. While the second run of 6
images was exposing Astrometrica was used to blink the images from the
first run to manually search for the object. When the second run had
finished the camera was centred 20 arcmin south. The third run of 6
exposures was then started and the second set was blinked with
The third run was stopped half way through its sequence because the object had been
located on the edge of the second run of images! The MPC prediction had
been good, only 16 arcmin west and 22 arcmin south of the nominal
position. I was lucky that just a fraction of the indicated 1.5°x3.5°
uncertainty area had needed to be searched before locating the object.
A full frame from the second run
showing the object close to
the edge of the field and an animation of the movement that revealed it appears below: