Histogram channels too far over to the left

[RedLeader1]

I am using a ZWO ASI071MC Pro camera with a Celestron 8" SCT + Starizona f/6.3 corrector and I tend to use a gain of 90 and either 15s or 30s exposure for the subs. I tend to find that all the channels on the histogram are right over to the left with barely any space on the left. I am likely to be missing something or not understanding something but I thought it was a good idea to have a reasonable gap on the left?

[admin]

Hi,

there's a big difference between 'only a little gap' (fine) and 'no gap at all' (not so good). You can use the horizontal zoom checkbox in the histogram to make it wider so you can have a closer look at the left hand side. As long as there is some gap between the left hand side and the start of the peak then you are OK on the brightness setting for the camera. If there is no gap, turn up the brightness...

One more thing to note - if you are using dark frames and you end up using an incorrect dark (perhaps taken at higher exposure, brightness or gain than the light) then that can also push the histogram too far to the left. The cure in that case is to use matched dark frames.

cheers,

Robin

[RedLeader1]

Thanks Robin, I would say it just about squeezes in the left side of the slope when zoomed in. I will work on the brightness as well to see what that yields. I forgot that the whole point of the histogram is the brightness! I was just under the impression that there needed to be at least up to 5% but seems not.
I use darks and flat frames but I have been only applying these after I have got the settings I want to use or do I need to have them in place when configuring settings to get good histogram readout?