Clean the CCD glass by dropping a few drips of acetone onto it and then gently wiping the microfibre cloth from one end to the other in a single stroke.
This pushes the dust off the glass and leaves it on the ceramic chip body – don’t sweep backwards at any time. Examine the window under a bright light, using a good quality lens to search for dust specks (a 50mm SLR lens works very well). If you can see any spots, repeat the acetone treatment until you are sure that the glass is clean. The inside surface of the camera window may also be cleaned at this time,
but do not use any solvent on it as the epoxy seal will streak onto the glass. An ‘air cannon’ will often work well on this window, rather than wiping it clean.
Carefully reassemble the camera, renewing the white thermal grease seal, if necessary. It is wise to leave it slightly open in a warm place for an hour to dry out the chamber before sealing it and testing. DON’T test it until it is sealed up, or you will cover the CCD in dew as it cools down!!
It may be tested for remaining dust spots by putting a pinhole lens over the barrel end and imaging the sky.