SharpCap Forums

Hi folks,

this week I have added some improvements to live stacking, with hopefully more to come over the next few weeks.

UnStack in Live Stacking

The first new thing is the 'Unstack' button which I have added
This button will remove the most recently added frame from the stack, allowing a frame that perhaps introduced a satellite or aeroplane trail to be eliminated. Unstacking a frame should be exact for 'Default' stacking, although it is not perfectly exact for 'Sigma Clipped' stacking. Unstacking is not available when using the Max Value/Meteor Detection stacking mode.

The unstack button becomes available when

* At least 2 frames have been added to the stack
* The most recent frame was aligned correctly and added to the stack
* SharpCap has not yet begun adding the next new frame to the stack.

You will notice it disable as SharpCap starts to process a new frame for stacking and then become enabled again once the processing is complete.

All feedback welcome - I realise it would be nice to be able to go back further into history and unstack a frame from longer ago - it's not impossible, but it is much more complex, so I thought that this would be a good starting point.

Live Stack auto-save options

This one is very simple - there are now settings in live stacking to allow you to control what stack formats are saved when the 'Auto Save' feature of live stacking happens.
By default, the ones shown above will be saved - 16 bit stack and with adjustments. You can customize this as needed.

Frame-to-Frame drift info

Finally, I've added some info to the live stacking drift graph that shows how much the image had drifted between the most recent frame and the one before that...
The range of values is because when there is some rotation included as well as just a linear offset, the distance varies from one part of the image to another. For good images, this value should generally be small when compared to the star FWHM value. I did some quick tests and a drift of 1/2 of the FWHM gave noticeably stretched stars, while a drift of less than 1/4 FWHM showed little distortion to star shape.

I am planning to improve this in a later update - perhaps a graph showing the drift size/direction in different parts of the frame and a warning if the drift is large compared to the FWHM.

Note that if a dither occurs between two frames then a high value would be expected (the value shows the size of the dither) and in that case it's not a problem...


cheers,

Robin

Thank you!
All beautiful and very useful news!

Carlo

This is great! I could have used it this weekend

BIG THANKS

admin wrote: Mon Jul 01, 2024 2:27 pm UnStack in Live Stacking

Thank you, thank you, thank you, thank you!!!

Hopefully I'll be able to get out and give it a good test in a few hours.

Watch, tonight will be the only night I won't be able to find a satellite.

Mike

There might be an issue with unstack and flip setting. In the preprocessing tab, I had Flip after dark/flat set to both, and did an unstack for a satellite trail. This was the result.

Oooh, that looks like it is unstacking the unflipped frame rather than the flipped one. It might mean that other processing isn't happening on the unstack too - let me check that out.

cheers,

Robin

Robin,
Could you have this new unstack function automatically unstack when satellite trail detected?

Hi,

hmm, interesting idea... Look at the *output* image from the stack (with stretch, etc) and if it has picked up a new, strong, linear feature, unstack the last frame... It might work, will have to do some testing.

I have just uploaded a new, updated, version that should fix the issue with unstack not coping properly with options set in the 'Preprocessing' controls (flip after dark/flat, flat frame, dark frame, basically the lot.) The code to do the processing before subtracting was there, but the *copy* of the original frame that it was using didn't have the processing data attached to it any more, so the processing code got called and did nothing because it thought there was nothing to do

Anyway, should be good now.

cheers,

Robin

Thanks Robin,
The “healing” of satellite trails now is great. Unfortunately sometimes it doesn’t quite get rid of trail.
Hope skies are clear out your way. Monsoon seasons starts now in Arizona