The event:
-------------

Shortly before 20:00 UT I set up my satellite tracking equipment and made
sure all was correct. The equipment consists of an altazimuth mounting,
equipped with stepper motors on the azimuth and elevation axis, carrying
a 145mm focal length lens operating at f/2.5 and covering a field of view
of 2.55 x 1.86 degrees. The camera is the well known MINTRON camera that has
quite remarkable low light level sensitivity. With my setup I am able to see
stars down to about magnitude 12.5 with an effective exposure of 0.96 seconds.
The image is shown in real time on a monitor and recorded on a DVD recorder.
The entire system is home constructed and there is nothing comparable in the
amateur satellite tracking community.

Using the freeware computer program CoSaTrak,(Computerised Satellite Tracking)
written by Willie Koorts of the South African Astronomical Observatory the 
camera started tracking at 20:00UT and the spacecraft could faintly be seen 
as a 12th magnitude object. Using a fixed exposure time of 1.28 seconds the 
mount tracked the spacecraft for the approximately 70 minutes that it was 
visible above my horizon - the track was terminated when Rosetta disappeared 
behind some trees. By then the craft had brightened to about magnitude +9.

The images are the result of adding 100 successive images to give an effective
exposure of 126 seconds.  Since the camera was tracking on the spacecraft,
the stars appear "trailed" during the 126 second exposure and the spacecraft
appears as a bright dot, just to the left of centre. A video time inserter
was running the entire time, set to Universal Time using a GPS receiver,
and displaying time to 0.1 seconds on the monitor, so, if necessary, apparent
celestial coordinates could accurately be derived as often as needed - the
equipment was designed for artificial satellite tracking so it is ideal for
positional work.

It is quite easy to see how the spacecraft sped up as it drew closer to
the Earth - compare the length of the star "trails" at the beginning and end
of the pass in the various images.

Due to the low elevation trouble was experienced with the bright city lights
of Cape Town which prevented me from using a longer exposure as the field of
view would then have been completely flooded out with city light pollution.

All in all an interesting experience. My special thanks to Mike McCants
of Texas, USA for supplying me with the ephemeris, and to Willie Koorts
for his fantastic program which makes spacecraft tracking so much easier.