New Feature : Stellar Colour Calibration for Live Stacking

[Robert]

Robin,

Beautifully brilliant! Can't wait to try it.

Robert

[admin]

Robin,

Perhaps you covered this already. Regarding the star database(s), is there anything I need to do to get the latest which include the colour information?

Aside from initially downloading the 0.25 database I've never updated anything other than SharpCap itself with each new drop.

Mike

Hi Mike,

right now, SharpCap only uses colour from the normal star database (not the extended 0.25 one - in fact the current version of that doesn't contain colour info). The normal star database is installed and updated with SharpCap itself, so you don't need to do anything beyond installing the latest version and it should all work.

cheers,

Robin

[givoly]

I have yet to use this, but this sounds AWESOME ideed! Well done. Looking forward to trying it out, and thanks for continuing to advane this app!

[Gfischer]

Hi robin,
I tried the new pcc tonight. A couple of questions.
1 I noticed if I use background subtraction in the camera controls the color balance is off. I assume the background subtraction needs to be off.

2 I could get the red blue balance good but the green was always to low no matter which star color I select. Best was with k0v. I use an lquad filter could that be issue?

3 when using ccp on a bright object if I use the auto stretch option the histogram is pegged to left and the white and midtone lines are over laid on each other. M8 with 12”dob 533 lquad optolong

I like the way the way the colors stay consistent when growing stack using this tool. I’m still learning how to use ccp but already it makes quite a difference.


Thanks for all your hard work

[admin]

Hi,

yes, if you have dual/tri/quad band filters then you can get 'interesting' results... The filter is cutting out more in some colours than others, and the colour calibration will naturally try to compensate for this to give the stars back their normal colours. Looking at the transmission curve for the L-Quad, it looks like it cuts out a lot in the orange end of red and also a chunk of blue around the Mercury line at ~430nm, but less in the green, so calibration will pull down the green to try to adjust. Maybe I could add a filter selection to a future update that would know this sort of thing and correct the calculations appropriately. Something to think about

I haven't tried using background subtraction in the camera controls with the new calibration yet - it should not be necessary if you are just using the basic 'constant offset' subtraction modes as the calibration will deal with that sort of background for you - only use the background subtraction in one of the gradient modes with colour calibrated stacking.

Colour calibration does try to put the stack histogram as far left as possible without black clipping - you may need to use the 'logarithmic' and 'zoom' options in the live stack histogram to see the peak clearly and make adjustments. Getting the histogram as far left as possible is the result of removing as much background as possible, and that makes colour balancing easier to adjust (both manually and automatically)

cheers,

Robin

[Gfischer]

Robin,
Thanks for the reply. An interesting problem to try and adjust pcc for different filters. You would almost need a sample of without filter to make corrections. For my setup I use the k0v star with pcc then use the lightning bolt balance in histogram. Then color on screen is balanced and remains so during entire stack. I leave the auto stretch option off because it over does it. Works great keeping stack consistent.

Thanks for the wonderful new tool

[Gfischer]

Hi robin,
I used the pcc again today. As before when calculating color I don’t get enough green. If I use the lightning bolt the color is perfect. The big advantage is the color stays good throughout stack without re calculating pcc. On thing might make tool easier. I use a kov star setting and no auto stretch option. When restarting sc the settings go back to default. Maybe save settings?

Took a couple of pics of screen to show results of pcc
https://drive.google.com/drive/folders/ ... tlBnhROgzB

Thanks

[admin]

Hi,

I think I will really need to do some extra work before the results will be any good when you are using dual/tri/quad band filters (or for that matter any of the more aggressive light pollution filters). Unfortunately, the link above was the sort where I need to request access (which I have done), so I couldn't see the images just yet.

thanks,

Robin

[Gfischer]

Sorry about the link. Never used google drive before link should work now

[Gfischer]

Robin,
I still think the pcc tool is valuable when using a quad band. Before this tool I would constantly have to readjust color balance while stack grew. Now I just click pcc and then lightning bolt and color stays balanced. Really helpful when doing out reach.
I was thinking if the user took an image with then without filter sc could calculate the effect on color balance. This data could be stored in sc and applied to pcc calculations