Problems with Dark/Flat correction during livestacking in SC3.3?

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DocHighCo
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Problems with Dark/Flat correction during livestacking in SC3.3?

#1

Post by DocHighCo »

Hello,

during livestacking I came across a strange behaviour with SC3.3. First I show what I expected, which I verified with SC3.2.
This is a 5 min livestack, 5 sec. frames with an ASI294MC pro, online dark and flate frame correction applied:
Image
Apart from some banding this is what I would expect. However, doing the same in SC3.3 with exactly the same setup and settings during the same night this shockingly resulted in this (this is a crop to show more detail):
Image
I found that the dark correction seems to be mostly responsible for this. Without dark correction it looks like this (this is also a crop):
Image
But, there still seem to be some remainig issues with the flat correction as well. In contrast to SC3.2 there still is some sort of halo in the picture (remember - same settings, same flat):
Image

All pictures were stretched with the autostretch function of Pixinsight. Any idea what is wrong here or what I did wrong?

Best regards

Heiko
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#2

Post by admin »

Hi Heiko,

what camera were you using? I wonder if something has changed the way that the offset/black level/brightness control affects the background brightness of the image?

Some things to check would be the following:

Do you see the problem if you capture some new darks and flats in SC3.3? I wonder if the problem is related to mixing dark/flat captured in a previous version with light frames captured in the new version?

Could you capture a single light, dark and flat frame in each version of SharpCap and share them (along with the capture settings files for each). Note that I mean a real single dark and flat frame (using the snapshot button, not an averaged frame using the Capture Dark/ Capture Flat functionality)? That set of six images and the accompanying settings data should reveal a fair bit about any changes between the two versions.

Cheers, Robin
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DocHighCo
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#3

Post by DocHighCo »

Hello Robin,

I used a cooled ZWO ASI294MC Pro. The darks and flats were taken already with SC3.3. But, they work also with livestacking in SC3.2 with the same camera settings without problems. I can of course shoot new single flat and dark frames with each version (no masters as I understood). Lights will be difficult as the clouds are back. Will daytime lights do?
As an additional information to you: The first frame of a livestack seems to have come in OK when using dark substraction with livestacking. But, from the second on things went wrong.
Nobody else found anything wrong with livestacking and dark/flat correction in SC3.3 so far?

Regards

Heiko
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#4

Post by admin »

Hi Heiko,

OK, that's interesting. Do you have the RAW captured frames saved from the live stacking session? If you do we could try running them through the folder monitor camera in 3.2 and 3.3 and see if that reproduces the issue - if it does then we are on the road to working out why.

cheers,

Robin
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DocHighCo
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#5

Post by DocHighCo »

Hello Robin,

unfortunately I didn´t save the raw frames, only the livestacks. One reason I use livestacking is to reduce the amount of data when taking many short exposures. I compared the setting files and fits-headers of the stack with SC3.2 (that is ok) and SC3.3 (that is not ok). They are identical.
I tried to repeat the exercise in daytime. But, everything worked then. I took master darks with SC3.2 and SC3.3. As far as I can judge they are identical (just subtracted them).
When I have some time I will try to repeat the exercise at night and save raw frames.

Regards

Heiko
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#6

Post by admin »

Hi Heiko,

thanks - I will also try to testify get some clear sky. The other thing to look out for I suppose is to see whether any of the colour balance/stretch/image enhancement settings are different between the two versions of SharpCap that might be causing the problem.

Cheers, Robin
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DocHighCo
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#7

Post by DocHighCo »

OK,

Would those settings affect the saved livestack? I thought they only influence the picture on the screen.

Regards

Heiko
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#8

Post by BlackWikkett »

Hi,
I haven't spent much time in SC 3.3 but have a lot experience with flats, darks, live stacking and ASI294 in SC 3.2.xxxx. What I've found is any changes to the SDK for ZWO cameras can have unexpected results with SharpCap live stacking when using dark and flat calibration frames. For flats make sure you use 50 / 50 for the for red and blue color balance and offset of 0. When creating the master dark with the dark capture tool make sure you use the same settings for brightness / offset and red and blue color balance. Also make sure you're using the exact same version of SharpCap with for lights and calibration frames. This is especially true if there are any update notes mentioning SDK changes. Some of the SDK changes may not be noted since 3.3.xxxx is in beta and Robin is focused on the new features and bug fixes.

Good luck, Chris
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DocHighCo
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#9

Post by DocHighCo »

Thanks Chris,

I will give it a try and consider your tips. Hopefully this is weaned out until the release version of SC 3.3.

Regards

Heiko
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Re: Problems with Dark/Flat correction during livestacking in SC3.3?

#10

Post by admin »

DocHighCo wrote: Wed Jan 13, 2021 10:00 pm OK,

Would those settings affect the saved livestack? I thought they only influence the picture on the screen.

Regards

Heiko
Hi,

depends on which save option you are using...

Save as 16 bit or 32 bit stack - these are not affected
Save with adjustments or save exactly as seen - these are affected.

Cheers, Robin
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