automatic choice of the best dark

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soulearth
Posts: 44
Joined: Sat Jul 18, 2020 2:17 pm

automatic choice of the best dark

#1

Post by soulearth »

Hello,
I have an uncooled OSC. Its temperature therefore drops during the night. I told myself that sharpcap could automatically choose the most suitable dark file in library.
It could be pretty basic. For example, the condition could be to have the same exposure and the same gain and sharpcap could choose the dark file with the more similar temperature.
What do you think ?
Best regards,
Soulearth
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admin
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Location: Vale of the White Horse, UK
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Re: automatic choice of the best dark

#2

Post by admin »

Hi,

right now this is not something that SharpCap can do by itself, although I think you could build something like this based on SharpCap's python scripting funcitonality if you have any experience in programming.

Out of interest, how are you planning on getting the dark frames at different temperatures anyway? That would be pretty challenging for an uncooled camera unless you somehow mixed it in with capturing the light frames - ie

repeat the following steps:
* Capture dark frames for 5 minutes
* Capture light frames for 15 minutes

As you went through the night you would keep capturing new darks as the temperature fell that would be close to matching the light frame temperature.

cheers,

Robin
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oopfan
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Re: automatic choice of the best dark

#3

Post by oopfan »

Back a couple years ago when I used an uncooled mono cam for AP, on cloudy nights I would set up the scope to capture darks all night. The next day, I'd group the frames by temperature. Often times it would take several nights to accumulate at least 30 frames per temperature. And of course, this is just for a single exposure setting! As a result of this massive undertaking, I opted to use a single exposure for all of my AP.

I am "old school" so I don't take advantage of Live Stacking or any of the great features of SharpCap. I just use it to capture lights, darks, flats, and bias. All processing is done offline, the next day. I understand what the OP wants to do, but I never took it that far.

One thing to ask: "Does my camera have a temperature sensor, and is the temperature written to the FITS file header?" If it is not, then you need to do what I did. Build an Arduino-based temperature logger. I bought a kit from Adafruit. If you need more information, I can help.

In practice, this technique worked well, but uncooled cameras are very sensitive to temperature, particularly in summer months. As I learned, the process of capturing and assigning temperature-dependent darks is burdensome. As a result, I jumped at the chance to purchase a cooled camera, even though it is not set-point. The quality is superior to anything I previously accomplished with my uncooled camera.

EDIT: My cooled Atik 314E is 10 years old and previously used. It cost $400. I still use it today. So, you don't need to spend $2000 unless you want to.

Brian
soulearth
Posts: 44
Joined: Sat Jul 18, 2020 2:17 pm

Re: automatic choice of the best dark

#4

Post by soulearth »

Hello.

It's exactly that. For convenience and because this setting works well, I always use the same exposure and gain.
So I will spend the time to do about ten dark during a cold evening
As the camera is stored in a heated place it will gradually cool down. I would then have dark for a while.
The camera temperature is shown in sharpcap so it's pretty straightforward.

Best regards.
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