Truncated Display Histrongram

[garyhawkins]

Does anyone know why Display Histogram is truncated as shown below (center RHS)? I'm using the ZWO ASI533MC camera and the latest beta version of SC. This appeared after a bit of a break from EAA associated with moving locations.

DisplayHistCapture.JPG (131.79 KiB) Viewed 918 times

[admin]

Hi,

that's a bit odd - if it happens again, check to see if the histogram looks the same way without live stacking active.

I suspect that it may be a bit of an artifact of the live stacking stretch - if you have a small number of bright (hot?) pixels that are brighter than all the others then that would set the autostretch white level , but the bulk of the bright pixels in the image are at a lower level and will therefore come out dimmer once the live stack stretch is applied.

cheers,

Robin

[garyhawkins]

Hi Robin,

It's weird - I had never seen this until I got all my equipment going again after two months in storage due to a house move. Since then, I've seen it consistently. I'll see what happens with live stacking off and get back to you.

Cs Gary

[garyhawkins]

While I have not tested this yet, one of the other CloudyNights members reported, "I see the same after upgrading to 4.0.8026.0. It is present in live stack, but not the live view." He had an almost identical picture of the Display Histrogram.

[admin]

Ah,

Ok, that helps - tracking back I can see I made a change to the way the histogram and output image was calculated for sigma clipped stacking in 4.0.7906 that seems to be the cause - there is a slight mismatch between the histogram drawing logic and the actual stretch calculations in certain cases which means you do not quite get the stretch you think you are, leading to the odd results.

I have a fix now that seems to resolve the problem - will be in next week's update.

cheers,

Robin

[garyhawkins]

Hi Robin,

OK great, I'll check the new version when it comes out.

CS Gary