Handbook for the TRIUS SX-825 Issue 1 January 2015
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Camera maintenance:
Very little maintenance is needed to keep the TRIUS SX-825 in excellent operating order, however two
problems, which are common to all CCD equipment, might show up on occasion. These are dust 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 (very 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’ 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. A light polluted sky
will also make these marks much more obvious. There is no great difficulty in removing such particles
on the outside surface by the careful use of a lens cleaning cloth, ‘lens pen’, 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 acetone or isopropyl alcohol. A very suitable cloth is the ‘Micro-Fibre’ type marketed by
PENTAX etc., and suitable alcohol is available from Maplin or Radio Shack etc. as tape head cleaning
fluid. Most pharmacist shops will have small bottles of pure acetone. 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 and the M8 nut from the camera back plate and ease the plate out of the
camera body. Unplug the fan lead from the camera PCB.
3) Withdraw the body cylinder and unscrew the two top spacer pillars from the PCB. Now gently lift
the PCB off the 20 way connector NOTING THE ORIENTATION OF THE BOARD for correct
replacement later. Now remove the lower two spacers from the heat sink plate assembly.
4) The camera heat sink assembly can now be lifted away from the camera front barrel and the CCD
will be exposed. 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.
6) Before re-assembly, make certain that the inside surface of the front window is also clean, and then
carefully replace the camera front barrel and screw it into place. (If the heat sink seal is disturbed,
renew it with fresh compound before reassembling).
7) Replace all the camera parts in reverse order and the job is done.
Dealing with condensation:
The
TRIUS SX-825 is designed to avoid condensation by minimising the volume of gas trapped within
the CCD cavity and by preventing moisture ingress. This normally works very well, but storage of the
camera in a humid location can lead to the trapped argon becoming moist by diffusion through the
optical window mounting thread etc. and can result in condensation on the CCD window. If this
becomes a problem, try storing the camera in a warm, dry place, or in a plastic lunch box containing a
sachet of silica gel desiccant. If this is not effective, it is possible to flush the CCD chamber with dry
argon from a small welding gas cylinder. Such argon gas cylinders, valves and suitable plastic tubing,
are readily available from many car spares suppliers, such as Halfords, in the UK.Two ports are
