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Dark Centers in Sub Frames

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#1 Salacious B Crumb

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Posted 09 November 2018 - 03:10 PM

I was just looking at my latest sub frames from Tuesday night and most of them have this weird dark center with washed out surroundings. Not all of them and cross more than one filter so I think I can rule filters out. Really odd as nothing has changed and I didn't see anything like this during the previous sessions. I can provide details as needed but any thoughts what could have happened?

 

Andro.JPG

 

 

- Mikko


Edited by Salacious B Crumb, 09 November 2018 - 03:11 PM.


#2 einarin

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Posted 09 November 2018 - 03:17 PM

Frost/condensation ?



#3 kidogofoto

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Posted 09 November 2018 - 03:29 PM

Frost/condensation ?

I agree, first thing that came to mind was dew.

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#4 Salacious B Crumb

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Posted 09 November 2018 - 04:09 PM

That was my first thought also but assumed that dew would look the opposite, not dark. I have one dew heater about 1/3 from the front of the scope. It's a small scope AT65 and so far one dew heater has been enough.

 

 

- Mikko



#5 Tapio

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Posted 09 November 2018 - 04:19 PM

Yeah but in camera, protective lens.

#6 pfile

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Posted 09 November 2018 - 04:41 PM

i know that with my STT-8300M when the dessicant plug needs to be recharged, the sensor cover glass window definitely frosts over as the chip cools. in theory the STT has a slip glass heater but i'm not sure if it's turned on. the phenomenon looks a little different than this - the frost seems to start at the outer edges of the sensor rather than the middle.

 

does that camera have any kind of dessicant in the cold chamber?

 

rob



#7 Jon Rista

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Posted 09 November 2018 - 04:53 PM

I would say frost as well. I think what is happening is that it is thick enough in the middle to start filtering out light, then it gets thinner and it scatters it more than filters it, hence the brightening...then the frost fades out by the edges of the sensor. At least, that is what I am "seeing" when I look at that image.


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#8 Salacious B Crumb

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Posted 09 November 2018 - 06:26 PM

Ok, thanks Jon and others. I'll add another dew strip closer to the camera and see it that helps. Should clear out tonight after midnight just conveniently when I'm back from a short business strip to Mexico. Talk about some dark skies there in rural areas. Stay tuned...

 

 

- Mikko



#9 Vassar1978

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Posted 10 November 2018 - 05:07 AM

Had the same thing happen to me this week.  Very humid day, then cooler night.  Camera was the ASI1600MM Cool version two, without the dew heater sold by ZWO (which I ordered).  I'm going to try changing the desiccant plug out while waiting for the dew heater. 

 

The dew heater fixed this issue with my other camera, an ASI1600MC Cool.  Pretty sure frost from the cooled camera is your problem.  The ZWO dew heater is inexpensive and might work better than a dew strap near the camera.

 

Good luck!

 

Rowland




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