The Moon occults Saturn Dec. 9th 1997
On december 8/9th 1997 the moon occulted saturn. The disappearance took
place on the dark limb and provided for a nice series of cut through pictures
for saturn. The sequence of pictures was taken with an 8 inch f10 schmidt-cassegrain.
To increase the image scale to allow saturn to be better resolved a 2x
teleconverter was used. For the choice of film a compromise has to be made
between exposure time and graininess of the film. The film chosen was Kodak
Elite 100 slide film. To avoid vibrations from shutter operation and the
rapid winding of the camera to interfere with the pictures a very stable
equatorial mounting was used. At 100ASA the exposure required for saturn
in the described setup was about 1/4 second. Longer exposures saturated
the image of the moon too much. Saturn being much further from the sun
than the moon receives much less light per area and thus is much fainter
in surface brightness. Luckily its high albedo (reflectivity) vs a rather
dark surface of the moon compensates a little for this effect. Nevertheless
at 1/4 second saturn still is about 1 stop underexposed whereas the moon
is already close to saturation in the brighter portions. The resulting
slides were then transferred onto photoCD. For further processing the 1500x1000
version of the photoCD image was used. To compensate for varying exposure
times all images were brought to similar brightness levels and saturn was
cut out into smaller pictures from pictures as those shown below. Click
on the picture to see a 500 x 500 pixel image.
These are the cut out pictures of saturn slowly being occulted by the moon.
The varying seeing quality resulted in the differences in definition in
the images.
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