Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
ramdom
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Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by ramdom » Mon Sep 25, 2017 7:30 am

Hi, I am wondering about the PNG (or FITS) files saved when you check on "save individual frames" - does it apply the dark frame subtraction? I notice in another answer you said that "save raw frames" does not apply the dark frame subtraction but I just wanted to make sure since the current interface I have says "save individual frames" and it means the same thing (unless there's a "save raw frames" option I don't know about). Thanks!

--Ram

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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by admin » Mon Sep 25, 2017 9:29 pm

It saves the raw frame before any processing is done to it.

cheers,

Robin

fyrblade
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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by fyrblade » Tue Sep 26, 2017 1:35 pm

Can you recommend something for the FITS file processing?

I used PIPP but I'm wondering if there is something better - it wouldn't open one of my larger files that was stacked.

ramdom
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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by ramdom » Wed Sep 27, 2017 11:11 am

I normally use Nebulosity for processing but lately I've started getting into PixInsight and have a good idea as to how it works (or least starting to "get it"). It's a huge learning curve though (PI that is).

I've also used Registax and I found that's good for stacking and some processing. For the most part, I feel Nebulosity gets it right in terms of balance between ease of use and complexity of features. But PI is more powerful and has a lot more features in it and I think it could technically do everything I currently do using a number of tools like Nebulosity and PhotoShop.

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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by admin » Wed Sep 27, 2017 4:05 pm

If you are looking for free options then you could consider DeepSkyStacker.

cheers,

Robin

sharpie78
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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by sharpie78 » Tue Jun 26, 2018 9:23 pm

Hi Robin
Just wondering if you could clarify this issue for me....Raw frames are not flat or dark subtracted. Is that correct?

I have 8 hrs of data captured over 4 nights using livestack. The resulting stacks are very nice individually but I'd like to process the raw frames in pixinsight in hope of weeding out the few weaker subs and achieving 6-7 hrs of integrated data to play with.

The reason I ask for clarification is because when I was manually calibrating the subs with the masterdark and masterflat, that sharpcap used during livestacking, my subs became extremely black. Even an enhanced stretch in pixinsight doesn't bring out much detail compared to the raw frame. Would a mastedark frame being used twice have this effect ?

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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by admin » Tue Jun 26, 2018 10:05 pm

Hi,

the design is to save those frames without any dark/flat applied and having just checked the code in 3.2 it looks like it is doing it right (the raw frame gets saved first and then the dark/flat get applied to a copy of the frame later on). It is quite a complicated flow so I could have missed something in the code - a quick test is to capture and use a 'not dark' dark - that way when you subtract the dark the result will be practically black and the live stack will be all noise. If the raw frames are also black then something is wrong. If they have stars (or whatever image you are using - no need for it to be astronomical) then they are being saved correctly without dark subtraction.

cheers,

Robin

sharpie78
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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by sharpie78 » Tue Jun 26, 2018 10:34 pm

Te raw frames themselves are fine Robin. An autostretch in pixinsight brings out a lot of stars and detail. It is only when I subtract the masterdark that sharpcap used during livestack that the subs go really black. Do I just need to capture another masterdark instead of using the one sharpcap created maybe?

sharpie78
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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by sharpie78 » Tue Jun 26, 2018 10:39 pm

another thought........I have "save 10/12/14 bit...without stretching.....etc" checked in settings. could this be the problem ? pixinsight is expecting the data to be 12bit stretched to 16bit but is just getting 12bit data ? I don't know how all that stuff works but just seems like a logical way to work through whatever is going on

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Re: Live stacking - does "save individual frames" apply dark frame subtraction or is it just the light frame?

Post by admin » Wed Jun 27, 2018 5:53 am

Check your master dark in FitsLiberator or similar - I think it will be 16 bit because it is an average of multiple frames so saving it at 12 bit would throw away data - this means that you may be subtracting a 16 bit master dark from 12 bit frames.

I'm sure that you must be able to make PixInsight multiply all the input frames by 16 before subtracting the dark *somehow* (you can do anything in PI), but I'm afraid I don't know how off the top of my head.

cheers,

Robin

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