Auto stretch and stellar cc

[Gfischer]

Hi Robin,
A
Quick Question. When the first frame of a livestack arrives I run stellar cc then auto stretch. The black and midtone markers move to far left on histogram with a dark image. When next image arrives everything works great. Any way to avoid this or is this normal?

Thanks for info

[admin]

Hi,

I've never seen that happen personally - once the first frame is in and the stacked frame count is showing as 1 then the colour calibration seems to give decent results. The exception would be that if the initial frame is very noisy and/or with few stars, the CC may fail at that point due to not enough stars found or a poor correlation with the true star colours. However if that happened I would expect it not to change anything.

cheers,

Robin

[Gfischer]

Robin,
The cc works fine it’s the auto stretch which is the issue.

[admin]

Hi,

OK, well perhaps the best thing would be for you to send me one or two raw frames (the first couple from the stack) in the original FITS format, along with any dark or flat frames you are using. That would let me reconstruct the same situation and try to work out the why behind what is going on.

cheers,

Robin

[Gfischer]

Robin,
I think I know what was happening. I was running a sequence . Stack one frame pause then color cc then auto stretch then resume. The color cc would take some time to solve then the auto stretch didn’t have time to work before the next frame came in. I switched order of color cc and stretch so stretch is applied first then color cc. Since color was close from previous runs the first frame would be bright and close on color.