Mono Imaging Histogram

[Gr4h4m (Graham)]

So, I’ve got a bit of a noob question.....

I’m in the process of stacking a load of images I’ve taken over the past few days using unity gain (111) and 600s exposures on a ZWO ASI183MM Pro with a 7nm Ha filter.

This is my first time processing a deep sky image and I’m used to dealing with histograms in ‘normal’ photography.

I’ve noticed my histogram is pushed to the extreme left, even when auto stretched.

Do I need to be aiming to get that auto stretch histogram one third of the way across to the right to start off with or is this pretty normal?

Not sure if I need to experiment with increasing the gain.

[Joshua Bunn (Joshua)]

Hi Graham.


Not sure what software you're using to process the images, but do the blackest pixels have an ADU value? You don't need to get it 1/3 of the way, just give yourself about 50 counts on the 0 - 255 histogram scale, that will give you room to move for later processing. Be sure to never save the image with cliped data or you will loose the data in those pixels


Josh

[Atmos (Colin)]

That's normal, especially with narrowband mono data as opposed to DSLR OSC data. Virtually ALL of your actual data is in the bottom 5-10% of the histogram, the other 90-95% brighter stars.

[Gr4h4m (Graham)]

Thanks for that.

I've attached a screenshot of what is showing on the histogram in Pixinsight when the image has been auto stretched.

Not sure if I'm doing this the right way though. I'm still getting used to Pixinsight.

[Atmos (Colin)]

What you’re seeing there is pretty much prefect so good job

[Gr4h4m (Graham)]

Thanks for that mate.

I've got around 4.5hrs on it so far but just wanted to make sure I was heading in the right direction before I tried to get another 2-3hrs again tonight.