Dealing with DSLR sensor glow?

[pipnina]

Since getting my star adventurer I've been able to take much longer subs than before. I might manage 25-30 seconds unmotorized but I can go up to 3+ minutes with the SA before my sensor gets saturated. This has been great for the depth of my images but it's bringing out the worst in my camera. See the image below:

At first I thought the defects might be the dew on my lens that night, stray street lamp light or my processing. But having taken some test dark frames I have noticed a pattern:

Looking at this "master dark" I created out of 40~ minutes of exposure at the same settings as the top image, you can see a lot of the glow in the top image aligns with the glow in the dark frame. This sounds like the solution has been found, but as you know DSLRs don't have cooling... And the effects of this on the dark frames are profound.

The first sub in the above dark frame:

Compared to the last sub taken after 40 minutes of exposure:

A considerable difference. And it's not like I can just tell the intervalometer to wait 5 minutes between shots as, while that would prevent the dark frames from getting progressively brighter, outside will be a different temperature to inside as well as the fact I won't be waiting 5 minutes between 3 minute shots when I'm taking lights.

 

Not sure what the solution is, if there is one. Perhaps it's better to simply use this method of indoor darks? Maybe turning on the camera's "noise reduction" feature is the best compromise (since that takes its own darks, although that wastes light time still...)?

 

It might be possible to remove the glow like any gradient in post-processing. But I don't think I have any of the software to do that with. (I've tried in GIMP, but it doesn't tend to work very well)

 

Thanks

[iapa]

There are some DIY projects to cool DSLR

I used one by Martin Pyott from youtube

c£100 for the first build - you do end up with more that you need if you go by the shopping list (use t of the second camera LOL)

 

 

[vlaiv]

That is why we love our set-point cooled cameras

There is only one thing that I can think of that might do any good to this situation except modding your DSLR with some sort of cooling.

This is dark frame optimization. Just stack your master dark with average method and apply dark frame optimization, and it can remove such amp glow gradients. It tries to guess (sort of educated guess) how much master dark to apply to each frame based on just such gradients. Just try it and see if there is considerable improvement.

[pipnina]

Just now, vlaiv said:

dark frame optimization. Just stack your master dark with average method and apply dark frame optimization.

Is this a feature in DSS/PixInsight/Photoshop or is it a method that can be performed in any image editor?

 

4 minutes ago, iapa said:

There are some DIY projects to cool DSLR

Thanks for the info, but I'm not too keen on nodding my camera- I still use it for terrestrial photography.

[vlaiv]

10 minutes ago, pipnina said:

Is this a feature in DSS/PixInsight/Photoshop or is it a method that can be performed in any image editor?

This is calibration algorithm, it is implemented in DSS, not sure about other programs, but it can probably be found there as well.

You should probably use either average or Auto Adaptive Weighted Average (not sure about the second one). Maybe even median if that is what you normally use for darks. Just use check box "Dark optimization" (marked with green arrow).

What it basically does is measure "information" inside calibrated file after dark removal, and uses quotient (which you can, by the way, enter on right hand side of it if you have any idea how much of dark frame to apply), and applies dark frame multiplied by some value (dark frame level scales with temperature and time). It uses such quotient for which there is the least of "information" inside image (or if you will background is the most featureless as it can be - meaning no gradients are present, only flat background).

[pipnina]

1 minute ago, vlaiv said:

 

I'll give that a try! Cheers!

[iapa]

18 hours ago, pipnina said:

 

 

Thanks for the info, but I'm not too keen on nodding my camera- I still use it for terrestrial photography.

The one I mentioned fits onto the csmera

no direct mod of camera required