SharpCap Forums

I am trying to dial in my flats for ASI1600mm-c pro. Things appeared to work well and I think banding issues are related to the light source and diffusion method (iPad and white dress shirt).

I am trying to see what the histogram was doing at the time. All I can remember was reading that the exposure should be all the way to the right without touching 100%.

What does the "Means" cell indicate? I am at 3736.
Peaks cell is 60391
Peaks level 3721

Exposure was .208
Gain the same as lights at 75
Brightness same as lights at 40
Cooler same as lights at -10C

Guides are always referencing ADU so I am wondering how far out I am and what I can do to improve. Attached is autostretched flat and manually adjusted. '

Hi,

In the histogram CSV file, everything is measured in ADU units for the camera. The ADU values will be 0..255 in 8 bit modes, or will depend on the bit depth of the camera in high bit depth modes. Your camera has a 12 bit ADC, so the ADU values go from 0 to 4095.

The means are the average value of all pixels (per colour channel if you use a colour camera).

Peaks are the pixel count for the level that has the highest number of pixels of all the levels (the height of the histogram peak).
PeaksLevel values are the ADU value that the peak above occurs at (how far right on the histogram graph the peak is at).

Note that the peaks/peaklevels are only calculated based on pixels above 20% maximum brightness - that means that in planetary/deep sky imaging, the large peak from the black background is ignored.

For the purpose of checking flat frame exposures though, the best thing is to simply scroll all the way to the bottom of the histogram CSV and check that the last ten or twenty rows all have a count of zero (or very close to zero - single figures).

cheers,

Robin

OK thanks. Only a few of my last rows are zero. The rest are close though. I read somewhere that 0.2 exposure times for flats is basically the limit for this camera. I could be wrong. If true that would make sense in relation to the graph numbers. I am going to try lowering brightness and lengthening exposure slightly.