Flat frame live stack problem

Discussions, Bug Reports and Issues related to Beta versions of SharpCap
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Lee Housden
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Joined: Mon Feb 12, 2018 5:45 pm

Flat frame live stack problem

Post by Lee Housden » Thu Oct 04, 2018 9:00 pm

I have a problem with my flat frames when I apply dark and flat frame on say a 30 second exp no problem as soon as I open live stack I get these vertical lines from the flat frames in live stack I no it’s the flats as if I select none the lines disappear help as I’ve tried lots of times as still getting these lines thanks lee
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admin
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Re: Flat frame live stack problem

Post by admin » Thu Oct 04, 2018 9:08 pm

Hi Lee,

Live Stacking automatically applies a stretch to the displayed image, so it may be that the lines are very faint without live stacking but the stretch makes them more visible - of course that's not going to be the whole story, but it may help understand why they are visible in Live Stack and not otherwise.

I think we need to identify whether it requires both flats and darks to see the problem (or if it occurs with just flats). Also you should examine your flat (and dark) frames with an image viewer that can stretch the images to see if there are vertical patterns in one or both of those files.

Finally (for now) what camera are you usign?

cheers,

Robin

Lee Housden
Posts: 16
Joined: Mon Feb 12, 2018 5:45 pm

Re: Flat frame live stack problem

Post by Lee Housden » Fri Oct 05, 2018 6:45 am

Morning robin camera is Hypercam 183c pro i went out last night with another set of flats and tried again still the same problem dropped the flats from the stack and left the darks no problem I will have a look at the averages saved files today and look just can’t understand why they are present

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Re: Flat frame live stack problem

Post by admin » Fri Oct 05, 2018 6:48 am

Hi Lee,

thanks - I have a 183C here so I will run a quick test later to see if I see anything similar.

cheers

Robin

Lee Housden
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Joined: Mon Feb 12, 2018 5:45 pm

Re: Flat frame live stack problem

Post by Lee Housden » Fri Oct 05, 2018 8:32 am

Ok so I have opened up pixinsight loaded the average of 10 flat frame and the dark stretched them both and the vertical lines don’t appear to be present
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Lee Housden
Posts: 16
Joined: Mon Feb 12, 2018 5:45 pm

Re: Flat frame live stack problem

Post by Lee Housden » Fri Oct 05, 2018 8:22 pm

Ok so tried tonight with the same flats in 3.1 and no vertical lines but does show the dust bunnies be interested in your tests to see if there is an issue in beta or it’s something I’m doing wrong I much prefer beta and I have a open reach night coming up
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Re: Flat frame live stack problem

Post by admin » Fri Oct 05, 2018 8:40 pm

Hi,

well the sky is not co-operating for testing on the stars this evening, but I have tested with a camera lens indoors.

Workflow (3.2):

Camera with 25mm CS lens
Camera in RAW12, minimum gain, black level 25, exposure adjusted as required
White sheet of paper in front of lens about 2" from lens to give 'flat' (flat enough) illumination
Use the capture flat assistant - Capture 10 frames, bias option unticked, mono flat ticked, auto use ticked, adjust exposure as suggest.

Before the flat is applied there is obvious darkening (vignetting) of the frame corners - the flat frame corrects that properly to give an even brightness with the sheet of paper still in place. On removing the paper and viewing a normal indoor image I can see no indication of vertical stripes, even when stretching the dark areas of the image.

I also tried with the 'subtract bias frame' option checked in the capture flat assistant and that seemed fine too.

In summary I'm not seeing this problem with 3.2 using the steps above- perhaps I am doing something slightly different to you? If you can, try the steps above and see if they work correctly for you. Maybe we can then identify whatever it is that you are doing differently that is causing the problem.

cheers,

Robin

Lee Housden
Posts: 16
Joined: Mon Feb 12, 2018 5:45 pm

Re: Flat frame live stack problem

Post by Lee Housden » Fri Oct 05, 2018 9:09 pm

Ok robin I will try steps above and let you no hoe I get on 👍

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