Starlight Xpress SXV-M25C - Manual (Page 30)

Handbook for the SXV-M25C Issue 1 June 2004
30
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Camera maintenance:
Very little maintenance is needed to keep the SXV-M25C in excellent operating
order, however two problems, which are common to all CCD equipment, might show
up on occasion. These are dust particles and condensation.
Removing Dust:
1) Dust can be deposited on either the optical window (not a big problem to cure), or
on the CCD faceplate (difficult to eliminate entirely). When small particles collect on
the window they may not be noticed at all on deep sky (small F ratio) images, as they
will be very much out of focus. However, if a powerful contrast boost of the image is
carried out, they may well begin to show as the shadow ‘Do-nuts’ or disks mentioned
earlier. Images taken with a large F ratio optical system are more likely to be affected
by such dirt, owing to the smaller and sharper shadows that they cast. There is no
great difficulty in removing such particles on the outside surface by the careful use of
a lens cleaning cloth or ‘air duster’ and so you should have little trouble with this
aspect of maintenance. Dust on the CCD faceplate is a much greater nuisance, as it
casts very sharply defined and dark shadows and it entails dismantling the camera to
get rid of it! To clean the CCD you will need a good quality lens cloth (no silicone) or
tissues and some high-grade isopropyl alcohol. A very suitable cloth is the ‘Micro-
Fibre’ type marketed by PENTAX etc., and suitable alcohol is available from Tandy
(Radio Shack) etc. as tape head cleaning fluid. A bright light and a strong
watchmakers eyeglass will also be found to be essential.
Procedure:
1) Disconnect the lead from the camera head and remove it from the telescope. Place
it on a table with the optical window facing downward.
2) Remove the two M3 screws from the camera back plate and ease the plate out of
the camera body. Unplug the power lead from the camera PCB.
3) Withdraw the body cylinder and unscrew the two long spacer pillars from the heat
sink plate assembly.
4) The entire camera electronic assembly can now be lifted away from the camera
front barrel and the CCD will be readily accessible. Note that a layer of white heat-
sink compound is applied to the periphery of the heat sink disc and this should be left
undisturbed by subsequent operations.
5) You can now closely examine the CCD faceplate under the spotlight using the
watchmaker's glass when any dust motes will show clearly. If there is only an odd
particle or two and the CCD is otherwise clean, carefully brush away the dust with a
corner of your lens cloth. A smeared or very dusty CCD will need a few drops of
alcohol to clean thoroughly and you may have to make several attempts before the
surface is free of contamination. One gentle wipe from one end to the other, with no
return stroke, will be found to be the most effective action. DO NOT rub vigorously
and be very careful to avoid scratching the window.