Hi,

In the context of another thread I tried to use the FITS viewers histogram mode to analyze the histogram of a dark frame. But (at least IMHO) it is completely useless for that purpose. I wonder if I'm doing something wrong here.

What I want to do is view the histogram of the range 0-500du of a dark frame. I acquire a frame, it's shown in FV, and I activate the histogram. But (probably because of hot pixels etc) with a range 0-40000 or so. I can zoom in, but the resolution doesn't change. I get a pyramid that is zero at 34 and 260 and max at about 148. No way to judge the histogram.
So I change the sliders to show the range 0-500. Or rather, I want to change it. I cannot decrease the low level at all. It sits on 32, if I set it to zero, it jumps back there. I can change the maximum to 500. If I then press 'apply' I get a histogram with 5 peaks (OK, as it is integer data spaced 16 due to the 12-16 bit conversion). But those peaks are at 391, 401, 409, 416 and 423. WTF? And the range slider now shows me 32-37 as limits.
This has absolutely nothing in common with the actual data. Which really make me wonder what that histogram thing is useful for at all

For next time, post your image data. Was it a FITS or other raw data format?