Two hills, what's up?

[Ags]

I was messing round with my ZWO ASI178MM, shooting chunks of the milky way at F5, and I noticed this while stretching the data in Gimp (logarithmic scale):

The image had already been through several stretches at this point. I assume data starts at the vertical peak, but what kind of noise does the small bell curve before that represent?

 

 

[Ags]

These are 1 second subs by the way.

[newbie alert]

11 hours ago, Ags said:

I was messing round with my ZWO ASI178MM, shooting chunks of the milky way at F5, and I noticed this while stretching the data in Gimp (logarithmic scale):

The image had already been through several stretches at this point. I assume data starts at the vertical peak, but what kind of noise does the small bell curve before that represent?

 

 

Usually stacking artifacts 

[CraigT82]

Have you cropped the dodgy edges from the stacked image? 

Edit: I.e.stacking artifacts as per newbie alert

Edited August 14, 2021 by CraigT82

[ollypenrice]

That's characteristic of edge artifacts. I always crop them right off before starting, otherwise you can't be sure what the histogram is telling you.

Olly

[Ags]

I thought I wouldn't have edge artifacts because DSS was in intersection mode, but I suppose that's no guarantee.