Starlight Xpress SXV-H9C - Manual (Page 21)

Handbook for the SXV-H9 Issue 1 June 2002
21
Jupiter after an ‘Unsharp mask’
In general terms, the larger the image and the worse the seeing, then the wider the
radius for best results. My Jupiter shots are usually about one third the height of the
CCD frame and I find that the ‘radius 5, power 5’ values are good for most average
seeing conditions. If you have exceptionally good conditions, then a reduction to R=3,
P=3 will probably give a more natural look to the image, as too large a radius and
power tends to outline edges with dark or bright borders.
As a finishing touch, the application of a Median filter or a Weighted Mean Low Pass
filter can be useful to smooth out the high frequency noise after a strong Unsharp
Mask.
As with deep-sky images, it is advantageous to sum colour planetary images together
to improve the signal to noise ratio. In this case, the ‘averaging’ option should always
be used, or the result is likely to exceed the dynamic range of the software and
saturate the highlights. Aligning the images is always something of a problem, as
there are rarely any stars to use when imaging the planets, but Jupiter’s satellites can
be useful reference points. Otherwise, you will have to find a well-defined feature on
the planet, or estimate where the centre of the disk is located. Some more
sophisticated software can automatically align planetary images and you may find
these programs to be very useful.
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Using the add-on autoguider:
A very useful accessory is the add-on autoguider head, which takes its power and
control signals directly from the SXV camera, via the 18 way socket on its rear panel.
The autoguider is only 1.25” in diameter and has a video style ‘CS’ mount thread in
its nose, so video lenses may be attached. The guider may be used with either an off-
axis prism assembly mounted in front of the SXV camera, or with a separate guide
telescope, rigidly mounted alongside your imaging telescope. I personally use it with
a 70mm aperture, F12, inexpensive refractor as a guide ‘scope, but a shorter focal