Flat generation subtracting dark flat

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SanjeevJ
Posts: 10
Joined: Tue Mar 16, 2021 7:01 am

Flat generation subtracting dark flat

#1

Post by SanjeevJ »

hello,

Based on testing on RASA 8 and ZWO ASI 2600 MC Pro, I need 1S to 2S flat exposure with dark flat subtraction to get the best possible master flat. Whether it is due to imperfections in set up's, camera limitations, etc -- using sub-second flats with bias is not correcting perfectly-- we had a separate thread on this in the "how do i" forum. Then you add filters, the need for flat exposure will go up more. The range of my testing included flats ranging from 15 ms to 10s, with lights ranging from 10s to 15 ms. I found using 1 to 2 second flats worked best for this combo for my typical exposures on this fast system, and this necessitates dark flats.

Can you please add the dark flat option in a future SC release? Could be a simple check box that toggles between using bias and dark flat. Would make it easier for all enthusiasts and give us an option that is very common in the AP world.
clouzot
Posts: 46
Joined: Thu Aug 08, 2019 11:13 am

Re: Flat generation subtracting dark flat

#2

Post by clouzot »

Sanjeev,

as far as I understand, the option is already there (albeit not advertised in the documentation): if we're capturing flats while dark frame subtraction is on, each and every flat has the master dark subtracted before it is emplaced "on the stack". Unless I got it totally wrong, that's ultimately a flat minus dark flat we get at the end of the process?
SanjeevJ
Posts: 10
Joined: Tue Mar 16, 2021 7:01 am

Re: Flat generation subtracting dark flat

#3

Post by SanjeevJ »

In a way yes. This was about using an automation flow like we do with bias.

Eg. user selects (bias or dark flat), flat duration, checks histogram. SC prompts to kick off dark flat, captures dark flat, prompts for flat readiness, captures master flat, done. It can all be done today manually -- there is also chance of user error in picking the wrong dark, user accidentally changing settings between dark flat and flat, etc. Its one more thing for EAA observers to learn, where as the bias - based workflow is automated in SC.
Chris A
Posts: 43
Joined: Fri May 03, 2019 4:06 am

Re: Flat generation subtracting dark flat

#4

Post by Chris A »

Clouzot is correct, and I have used this method of taking my flats with matching dark flats, however, Sanjeev has brought up some excellent points in order to make this process as convenient as capturing flats with a bias in Sharpcap.

Chris A
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admin
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Re: Flat generation subtracting dark flat

#5

Post by admin »

Thanks folks - I have noted down this idea for a future improvement.

cheers,

Robin
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