Following a suggestion from Monty Robson (John
J. McCarthy Observatory), a set of images were taken of Mars on two
nights in September 2005 in an attempt to record Deimos, Mars' outer
satellite. Without any obscuration available to mask the glare from the
magnitude -1.6 planet and with Deimos 14 magnitudes fainter and only
reaching a maximum distance of about 60" from Mars it was a challenge.
A set of eleven four second exposures were taken at full CCD
resolution (binned 1x1) giving a scale of 1.07" per pixel and then
stacked together by averaging (rather than adding that would normally be
done for NEO work). As can be seen above, two stars can be made out as
well as Deimos, just outside the burnt out glare of Mars. The field of
view has been cropped to 4'x4'.
The measured astrometric position of Deimos was 0".6 south of the prediction
from the JPL Horizons ephemeris. A representation of the positions of the
stars, Mars and Deimos can be seen below, as predicted by Bill Gray's
Guide 8.0 planetarium program for the same moment as the images were
taken. As can be seen, Phobos, the closest of the two Martian moons is
lost in the glare from the planet, but Deimos shown, just a couple of
hours from maximum eastern elongation. Tick marks are at hourly intervals
from 0 - 09h UT on 2005 September 29 with Deimos marked with a 'D'