Is it possible to create a feature that allows the user to select an area within an image in the fitsviewer to give a targeted opportunity to critique background psuedo ADU e.g a moveable box of say 100x100 pixels that shows the user some appropriate stats. The mean/min/max of the 10,000 'background'pixels could be a useful value to quickly determine exposure. The Fitsviewer currently produces DN values for the whole image so why not for a user selected area. Maybe link said feature with the cursor over the image.

I agree absolutely with this request. In order to determine the right exposure, we have to compare the standard deviation of the background into a capture to the same value into an offset. The capture value must be within 3.5 and 5 the offset value. So we have to select an area of the image background. Today I have to load the two images into Iris software to do that. It would be convenient to be able to do so with Kstars.

Thank in advance.

That's an interesting factor to determine correct exposure. When you say within '3.5 and 5' what parameter are you evaluating?

You mesure the standard deviation (sigma) of a background area in capture and offset.

Sigma (image)~3.5 to 5 sigma(offset)

Try 1, 2, 3 or more minute exposition and examine the sigma against an offset. It is not needed to overpass the value 5.

I assume with 'offset' you refer to a dark? Indeed an interesting way of doing it. It seems to boil down to the standard approach of 'swamping read noise', using the dark/offset STDEV as read noise?

The right word is BIAS I think. Not dark.