Just Checking, is that dew?

Dew Heater Acquisition Meridian Flip Deep Sky
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AstRobert avatar
AstRobert avatar
Hi,
Unexpectedly yesterday night cleared up and I tossed out all my stuff and started a session. I stayd with it for the 5 pics before the Meridian flip as I wanted to observe and test it for the first time with NINA. Then I left everything to image throughout the short summer nights. i i found that every image after the flip and even one before looks like this:


Is that dew? And if, WHERE???
Because I had the dew heater running on full power, at least I thought.
The build up in the images is rather quick and it stays, so it is not going completely in. Also I am usually used to dew forming in the center and creping outwards and I looked on the lense during the meridian flip wait time and it was totally clear, but even one picture before that showed this.

Any suggestions or other explanations.

One alternative i have is, that it is dew on the camera shield as I though it would be a good idea to cool down to -20 and not jsut -10. and had the camera dew heater only set to 1 of 4? :-(

Cheers, Robert
andrea tasselli avatar
andrea tasselli avatar
It's condensation on the sensor. Run it at 0  and then after a while you might move it -10. If your integrations are less than 5 min isn't really worth doing though, at least with modern CMOS. Window's dew heater is essentially pointless in summer.
jmdl101 avatar
jmdl101 avatar
Funny enough the exact same thing happened to me last night. A little after midnight that dark oak started growing and I lost 4 hours of exposures. It's definitely dew or fog on your sensor window. I had my camera dew heater at half power because I have never had an issue before. After putting it on full power the oval faded and disappeared after about 10 minutes. 
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