My astronomy project:
Making of a heating band or dew heater

Content:

1. Introduction, attach a heater to the dew shield
2. Heater band for 5" refractor, field test outdoors
3. Lens USB dew heater
4. Dew USB heater narrow band model with regulator
5. Camera body heater

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

5: Camera body heater

The dew heaters I have built for my optics have worked very well during the last years. However, I have another problem related to dew. The camera sensor get dry stains from droplets that condensate on the sensor. Not during the night when doing astrophotograping, but when I take the equipment indoors afterwards. When the cold camera come in contact with the hot air indoors the vapor in the air start condensing on the cold devices including the camera's sensor. Very annoying, I have to clean the sensor very often and that's a lot of boring work.

I have thought about what I can do about it, ideas like: Blowing dry air inside the camera against the sensor, too complicated. Encapsulate the camera body in wrap plastic but make it complicated to seal around the cables. And at last, add some heat on the camera sensor when taking the camera indoors. The last is what I'm preparing here for an experiment. Indoors temperature about +20^oC, outdoors -20^o to +5^oC.

Dry stains:

This is typical how it looks like on the camera's sensor, and it wasn't more than 2 weeks since I cleaned it. The image is heavily stretched. It's the dark dots that are the new dry stains, the white ones come from that I used an old MasterFlat when I did the flat calibration. It's about 20 dark spots on the image. Will it be more of them or stay like this after I have done my new procedure when I heat the camera body ?

I will come back later with new photos how these dry stains develop after a couples of nights.

It's complicated to heat only the image sensor, but I can heat the camera body for a test if it helps to keep away the dry strains. After I took the camera indoors I put on the heat strap and apply 8 Watt of power to it during 20 minutes, after that I lower the power to 4 Watt and let the heat be on for 5 hours, at least. That's not much power, I can take that power from an USB backup battery if I want to start this heating procedure already before I take it indoors. If I find that this procedure helps to keep the dry stains away I can built a more specialized compact heater later and place it into the camera, then it needs even less power.

This was taken a couple of days before I started to use the camera body heater.

Cleaned the sensor and from this night I started to use the camera body heater. After taken the telescope and camera indoors I have the camera body heated for 5 hours at least.

Three days later we got a clear sky once again and I took the telescope outdoors. What do I see, 6 new dry stains or dust blobs, in this case I think most of them are dry stains. This was the first photo of this night.

This is from the same night but the last photo, 88 minutes later. No new dry stains or dust blobs has appeared.

What a disappointment, I had hoped that this camera body post heating had solved the problem. But I don't give up yet, next time I apply the heat already outdoors, 20 minutes before I take the equipment indoors.