My astronomy project:
Sensor dryer stains

Contents:

1. Dryer stains
2. Sealing the chamber and desiccant
3. Three nights outdoor tests
4. During work

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

3: Three nights outdoor tests

With this, sealing the chamber and put in some desiccant, will it make any difference ? I do three new outdoor tests. The temperature is from 0 to -4^o C during the night. I take 60 seconds exposures, not equal number of photos each night because of clouds.

Equipment:
Camera Nikon D800 full frame
Optic Pentax 645 AF 300mm f/4 ED IF

Night 1:

This day I cleaned the sensor and got rid of all stains. Take a serie of test photos and no new dryer stains visible on it. Take the camera indoors to room temperature, about 20^o C.

Night 2:

Second night, calibrated with old flats, the white blobs is from old stains now cleaned. The new ones is the grey ones. 8 of them, less than normally. Take the camera indoors, I let it sit on the telescope as usual to not get dust into the optics.

Humidity according to Väderhistorik: 2025-02-14, 85%

Night 3:

Third night, 5 new stains.

Humidity according to Väderhistorik: 2025-02-17, 84%

Night 4:

Fourth night, no new stains on the sensor.

Humidity according to Väderhistorik: 2025-02-18, 80%

It looks like that all new stains come when I take the camera indoors and let it heat up to indoor temperature. It depends of course a lot of the humidity of the atmosphere. 84% is twice as good as 85%, 80% don't give any dryer stains at all. So I shall stay indoors all nights with humidity over 80% ? Later I will build a weather station on the telescope that can mesaure the humidity and temperature.