Do dark and flat frame work during live stacking?

[ippiu]

Hi Robin.
I’ll show you some strange behaviour during live stacking, expecially when i wanted to correct and compare a live stacking image with or without dark frame and flat frame correction.
It seems nothing has been corrected by nor dark frame neither flat frame during live stacking.

10 dark frames acquired: they look correct. You can see amp glow and little noise.

dark.jpg (93.89 KiB) Viewed 2789 times

10 flat frames acquired, monochrome, bias checked: they look correct. You can see dust bunnies and vignetting.

flat.jpg (261.69 KiB) Viewed 2789 times

No dark, no flat: just live stacking, heavly stretched to show better amp glow and dust bunnies.

no dark_no flat.jpg (438.72 KiB) Viewed 2789 times

.....continue....(I don't know why i can't anymore add files here...i have to write another message)....

[ippiu]

Dark and flat applied: nothing changed. Heavly stretched to show better that amp glow and dust bunnies are still there.

dark_flat.jpg (443.69 KiB) Viewed 2788 times

Now i tried to use DSS to see if it is able to apply correctly the dark and flat: it cannot, amp glow and dust bunnies are still there.

DSS_dark_flat.jpg (422.79 KiB) Viewed 2788 times

So, dark and flat frames are correct. But they don't correct the image, they aren't applied correctly during live stacking.
And also DSS doesn't apply them correctly...

I also attach the log...(inside it, there are other live stacking sessions)

Log_2019-03-05T20_20_05-3648.log

(132.46 KiB) Downloaded 121 times

[admin]

Hi,

The answer is yes they do apply during live stacking. However neither correction is entirely perfect and during live stacking you tend to apply quite a strong stretch to the image which means that any imperfections in the correction do tend to show up more.

Best results are usually achieved by using the 'bias frame' option when capturing a flat and making sure that the dark frame is captured at exactly the same settings and temperature as the light frames.

Cheers, Robin

[ippiu]

Thanks robin.
Obviously, i capture the dark at the same temp, gain, exposure and also focus position as the lights.
The flats were captured with bias option checked, monochrome.
But it seems thar their effects on the light frame during live stacking are almost nothing.
Amp glow, vignetting and dust bunnies were still there.
During live stacking every 2 frames i applied dark and flat, then i cancelled them, then i reapplied them, and so on, just to see their results on the image being stacked: no effect.
But in 3.1 software version, dark and flat had great effects in the image live stacked, i loved them. Now i cannot get those wonderful results as in the previous version.

Thanks robin

[ippiu]

I used color space setting: RAW16, but image format .png, either in live view, or in live stacking.
Could this be the reason for inefficiency of dark and flat?

[admin]

Hi,

The same format shouldn't be a problem because SharpCap can save and load correctly from 16 bit PNG files.

I have made a number of changes to the flat frame correction since 3.1 but I was expecting them all to be improvements rather than lead to a new problem.

It would be helpful for me to try and diagnose what is going wrong if you could send me:

At least one unprocessed light frame
at least one unprocessed dark frame
at least one unprocessed flat frame
the master dark frame you used
the master flat frame you used

Probably the best approach would be to upload these files if you have them to somewhere like Google Drive or dropbox and then share a link with me via private message.

Thanks, Robin

[ippiu]

I have the final stacked image either in .png or in .fit, but i didn't save each single individual frame. So with "unprocessed light" what do you mean?
As for flat and dark, when you create them with the assisted procedure, sharpcap creates just 1 final file for dark and another final file for flat that are master dark and master flat. It creates only a .png file (it doesn't allow to save for example in .tif). So what do you mean with "unprocessed dark and flat"? Sharpcap doesn't create single unprocessed n dark or n flat (n is the number you choose in the assisted procedure to create them).
I have:
-.png or .fit (the only 2 possibility to save the final stacked image) stacked image
- 1 master dark and 1 master flat used (only in .png because sharpcap doesn't allow another file for example .tif).
So let me know what you need, please.

Thanks robin

[admin]

hi,

This will probably be something that you might be able to test out on your next imaging session then. What I need is the following

A raw unprocessed image frame (either by saving the raw frames when life stacking or using the snapshot button)
a raw unprocessed dark frame (press the snapshot button after you've created your master dark to save a single dark frame with the same settings)
a raw unprocessed flat frame (again press the snapshot button after creating your master flat to save a single frame with the same settings)
the master dark and master flat frames

Fits format would be best for these if possible. Hope that clarifies things.

Cheers, Robin

[BlackWikkett]

Seeing the initial dark frame I recognized this as a ASI294 and taking a cursory look at the log file this is confirmed. Normally the amp glow starburst pattern is seen in the upper right hand hand side of the frame. In the example provided the main amp glow starburst is in the lower left side and a minor amp glow is in the lower right. This looks to me as the image is flipped in both horizontal and vertical orientation so the amp glow appears in the lower left side of frame. Since there's also some amp glow in the lower right could you have clicked the flip button while you were exposing the the dark frame?

My experience with the 294 and using dark frames in live stacking you need to be very careful to apply the exact settings you will be using to capture your light frames. Exposure, gain, brightness need to be exact. Also recommend using the lowest brightness setting you can.

For flats make sure you are using mono and and bias. With my light panel and scope (RC6) I usually use 300 gain, 200+ ms exp, brightness 0 and shoot 50 frames to create the master flat.

Have a look at this viewtopic.php?f=5&t=1282 we worked this out a few months ago and this has been working very well.

Hope you are able to solve your problem

[ippiu]

A raw unprocessed image frame (either by saving the raw frames when life stacking or using the snapshot button)
a raw unprocessed dark frame (press the snapshot button after you've created your master dark to save a single dark frame with the same settings)
a raw unprocessed flat frame (again press the snapshot button after creating your master flat to save a single frame with the same settings)
the master dark and master flat frames

Fits format would be best for these if possible. Hope that clarifies things.

Cheers, Robin

Now i understand everything. As soon as i will image next time, i will take all of them.
I have no problem to take them in .fit format. But because of i usually don't do any serious post processing, i usually work with .png format: so to completely match my usual imaging session, and to avoid possible problems due to different image format, do you think it is better to take all images in .png format? So we can replicate exactly my field imaging session...

Thanks