2004 EL20 (very small Aten making close approach)
Put on the NEO Confirmation page at about 23:00 UT on 14 March 2004
as a mag 18.4 object moving at ovber 30"/minute, the initial prediction
was already showing the possible area that the NEO might be found in to
be over 2º in size.
Conditions that first night were poor at
Great Shefford with cloud frequently interrupting exposures. The object
could not be found in two separate search fields before clouds stopped
further work. The next night was cloudy and the object but the object
was confirmed on the NEOCP just after midnight, 16th March 2004.
Clear skies on the night of the 16th
allowed the stack above to be obtained from Shefford, by which time the
NEO was moving at 40"/minute, forcing exposures to be kept to just 6
seconds long, with multiple short exposures being combined to reveal the
Astrometric positions were sent to the
Minor Planet Centre at 21:34UT and the announcement Minor Planet
MPEC 2004-F12 was issued two hours later.
The JPL NEO Past Close Approach table
shows that 2004 EL20 was at its closest to the Earth almost
exactly when the image above was taken, at 20:16 UT +/- 1 minute on 16
March 2004 at 5.7 lunar distances away.