Cleaning dirty sensors and photometric filters

American Association of Variable Star Observers (AAVSO)
Tue, 05/17/2022 - 04:36

How do you clean the spots from your CCD sensors?  My SBIG ST8 has spots on the sensor, and I've been using Lens Wipes, soft cloth rag for glasses, etc and so far I'm still getting spots on the sensor.  Also my photometric fields still have spots on them.  Any advice on cleaning my CCD sensor lens



Are these "spots" dust…

Are these "spots" dust donuts? Or are they more like water or other liquid spots?

If donuts: you either need to clean them off in a cleanroom using compressed air and/or soft brush or live with them and cal them out with flats.

If liquid spots: What liquid? 



cleaning sensors

Hi Tim,

Before you go to the trouble of cleaning your sensor, check and make sure that it is spots on the sensor that are causing the problem.  Sensor spots do not exhibit a donut, but look like either sharp solid black dots (dust) or a water spot (mottled area with an in-focus rim).  You can sometimes look through the camera entrance window with a magnifier and focus directly on the sensor to see if there is something there.  If you see a dust donut instead, then use the calculator:

to locate the position of the dust spec causing the donut.  This can be the entrance window to the camera, for example.

If you do have water spots on the sensor itself, the safest way is to send the camera to SBIG repair and have them do the cleaning.  If you want to do it yourself, I've been successful cleaning sensors using Orion's cleaning kit, or one of the DSLR cleaning kits, but just do it like you would clean your mirror - carefully and without scrubbing.  An additional suggestion is to make sure that you are grounded so that there will be no static discharge through you onto the sensor.  The best solution there is an anti-static grounding bracelet (you can find them on Amazon and elsewhere).

In the future, water spots are almost always the result of worn-out dessicant.  If you live in the moist climate, be proactive and heat your dessicant regularly to keep it dry.