Live stacking issues with Optolong LPro filter

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Cey42
Posts: 52
Joined: Tue Nov 10, 2020 3:47 am

Re: Live stacking issues with Optolong LPro filter

#11

Post by Cey42 »

OK, I am now very confused. Here are my results of running the files I sent you. I applied the dark only and not the flat.
I am running v3.2.6421 (top image) and v4.0.7995 (bottom image).

Could there be some setting I have different?
SC2.png
SC2.png (135.79 KiB) Viewed 751 times
Thanks,
Cey
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Re: Live stacking issues with Optolong LPro filter

#12

Post by admin »

Hi,

are you testing with the 'Deep Sky Test Camera'? If so, what settings do you have for

* Gamma (default 1.0)
* Gain (default 100)
* Debayer Preview (default on)
* Exposure (default 1000ms)
* Colour space - should be RAW16

Check that these are defaults and are the same in 4.0 and 3.2.

Also, check that all the 'Testing controls' to add things like random noise, seeing blur, focus offset, etc are set to 'off', zero, etc.

cheers,

Robin
Cey42
Posts: 52
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Re: Live stacking issues with Optolong LPro filter

#13

Post by Cey42 »

I captured a new dark last night along with the capture settings. It is definitely an issue with the dark. If I do not use it in 4.0 it works fine. Using the dark in 3.2 works also.

Here are new files along with a video showing how I am reproing the issue using 4.0.8026 using the "Folder Monitor Camera"
https://1drv.ms/u/s!AmzOfpCoABCRgcwsPQ8 ... Q?e=2p8EWR

Tell me if there is anything else I can do to help figure out what is going on.

Thanks,
Cey
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Re: Live stacking issues with Optolong LPro filter

#14

Post by admin »

Hi,


Ok, I see the same as you trying those frames with the folder monitor camera in SC4.0

SC3.2 also does the same thing, with one gotcha - SC3.2 picks the wrong bayer pattern when loading the frames - if you look you will see pink stars by default with a grid visible on them. Picking 'Force RGGB' as the bayer pattern in SC3.2 then proceeds to produce identical results to the ones you are seeing in SC4.0 (and I see the same too).

Ok, so as far as I can see, no big change between 3.2 and 4.0 here apart from the fix to pick the right bayer pattern automatically.

Next up, the auto-colour balance not working.

It kind of seems OK that this is not really working as your combination of the LP filter and dark subtraction has basically eliminated the background signal in the red channel - this makes aligning the histogram peaks using the colour balance nearly impossible as the boost factor required for the red channel would be infinite.

The colour balance from histogram peaks is designed around either colour balancing remaining light pollution in the image to roughly white, or doing the same with nebulosity if you have a good amount of nebula/galaxy visible. In the sort of image you are using with a black background it's not so good. For that sort of image, the colour balance from star colours is better - it looks for non-saturated stars and tries to make the average colour of those white.

cheers,

Robin
Ddaniel84
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Re: Live stacking issues with Optolong LPro filter

#15

Post by Ddaniel84 »

A possibility may be that there are not enough pictures. 1 min stacked is too short. I've a L-eXtreme filter with a ZWO ASI 294MCS and a C8 f7, color adjustment begin good after 5 to 10 minutes stacked, may be more.
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Cey42
Posts: 52
Joined: Tue Nov 10, 2020 3:47 am

Re: Live stacking issues with Optolong LPro filter

#16

Post by Cey42 »

Robin, thank you for taking the time to investigate this. I have re-read your last reply several times trying to understand what is going on. I still don't understand. Let me take you through some of my thinking and you can tell me where I am wrong.

First here is the chart for the filter. This lets in the red part of the spectrum.
LPro.jpg
LPro.jpg (35.93 KiB) Viewed 711 times

Next here is a stack of the original files that I provided using no flats or darks. There looks like there is plenty of red signal here.
Stack-NoDark.jpg
Stack-NoDark.jpg (79.92 KiB) Viewed 711 times

Now this is the same stack but adding the dark. I don't understand why the red curve looks like it does and why the dark is doing this.
Stack-Dark.jpg
Stack-Dark.jpg (82.31 KiB) Viewed 711 times


Can you explain again why the dark causes this or if any of my thoughts are wrong?

Thank you,
Cey
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Re: Live stacking issues with Optolong LPro filter

#17

Post by admin »

Hi Cey,

to be honest with you I don't understand why the red channel is so dark either, but every test I've done on those images shows that the red channel in the dark frame is nearly as bright as it is in the light frame, while the blue/green channels are clearly brighter in the light frame than the dark. I think it is something to do with the capture rather than the processing of the frames.

Maybe capturing a new set of dark frames *without* using SharpCap's 'Capture Dark' functionality would help dig down a little deeper. Then we could make sure we get

* 10 or so light frames
* 10 or so dark frames captured at exactly the same settings

and go from there

cheers,

Robin
Cey42
Posts: 52
Joined: Tue Nov 10, 2020 3:47 am

Re: Live stacking issues with Optolong LPro filter

#18

Post by Cey42 »

I have captured "dark" frames using the Quick Capture feature. I used 12 seconds and 400 gain as in the lights I have shared so far.

Something I noticed, not sure if it is a red-herring, if I use darks of gain 300 or less, then the red curve comes out fine. I know that this does not match the lights. I went back to the night that I noticed the issue and first did the post about. All images done at 300 gain were fine. It was when I switched to 400 gain that the issue showed up.

This share has the individual dark capture and a 300 gain dark that works fine.
https://1drv.ms/u/s!AmzOfpCoABCRgcw4WzM ... Q?e=oKPO1A

Thank you for still investigating,
Cey
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Re: Live stacking issues with Optolong LPro filter

#19

Post by admin »

Hi,

I think this is a red herring - by using a lower gain in the darks than the lights you are pushing the dark frame peaks lower, which means that there is some signal left after subtraction leading to a 'normal' looking curve.

The dark frames look sensible - both the individual frames and the master frame. All the channels align, which is what we would expect. The suspicion is now on the light frames and understanding why the red channel is just so damned dim in those frames.

Can I just check that you have not adjusted the white balance Red and Blue controls away from their default value of 50 during the capture of light frames?

cheers,

Robin
Cey42
Posts: 52
Joined: Tue Nov 10, 2020 3:47 am

Re: Live stacking issues with Optolong LPro filter

#20

Post by Cey42 »

I was not clear on the second part of my 'red herring' comment. On July 25 I was imaging IC 1295, NGC6629 and M11 at 12seconds & gain 300 using the matching dark (12s, 300g) and there was not issue an the red channel. I then went to NGC7027, I had to boost the gain to 400, still at 12 seconds and matching dark (12s, 400g), then I noticed the red channel issue.

Checking the cameraSettings.txt file, I see
White Bal (B)=50
White Bal (R)=50

It is gong to be clear tonight. I am going to check again to see if using 300 gain (matching dark & light) does not show the issue while using 400 gain (matching dark & light) does show the issue.

Anything you want me try tonight?

Thanks,
Cey
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