SharpCap Forums

Hi folks.. I am using the 294MC Pro cooled to -20C, on a C11 with a starizona full field reducer. I am at 250 gain through a UHC-S filter.

I find that when I take images and live stack, they are green shifted slightly and in sharpcap the histogram only shows the right half of the curve ... The left half is out of view to the left and unreachable. Not sure was is wrong. I have to pump the gain to 375 MINIMUM to see any detail and its usually not color corrected. In fact only when I vastly overdo the gain will the left half of the curve begin to show slightly... Then I reach the issue below:

Second issue: When I go to color correct below using the lightning bolt at lower right of the Stack window, the curves dont auto adjust sometimes and sometimes they adjust the red only which shoots to the top and the entire image is bright red slanted... Hitting the diamond brings it back to the middle on RGB. This has never happened before.. I usually color correct using the lightning olt at lower right in the stacking window and its fine...

Any idea whats going wrong?
Thanks,
Marc

Hi Marc,

starting with the reason that the histogram curve is too far to the left - two main possibilities

1) You are using dark frames and they don't properly match the light frames (in fact they are *brighter* than the light frames) - this leads to over-subtraction and a black or nearly black result. Dark frames need to match the light frames in a number of camera settings, including : Exposure, bit depth, gain, 'brightness' (also called offset or black level on some cameras) and white balance settings.

or

2) You have the 'brightness' control set too low - perhaps to zero. This control introduces a small additional artificial value to every pixel, and adjusting it upwards is the way to move the histogram away from the left hand side and to make sure there is at least a small gap between the left hand side of the histogram peak and the left hand vertical axis of the histogram. This is usually best adjusted by setting the desired gain, exposure, etc, then viewing the main histogram (not live stacking) while adjusting.

I suspect that the problems you are seeing with difficulty in colour balancing are a consequence of the stack background being too dark due to the above problem - once you have that fixed, I think the colour balance will behave itself. As it is with the dark background, in some cases it will end up calculating 'impossible' solutions to the calculations and then end up deciding not to apply them.

cheers,

Robin