Quote:
Originally Posted by JohnG
My exposures are usually from about 1/400 to around 1/650, when you take the shot, check using the View button by looking at the Historgram, the peak should be about 1/3 to the right.
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Thanks, John. It's good to hear from an experienced user with exactly the same telescope/camera combination. That info is just what I needed. I was looking at the histogram but didn't know what was desirable. I did the flats indoors the next morning with the t-shirted OTA facing a lit wall. The exposures were almost 1 sec. How crucial is it that the temp is the same for flats and lights? Presumably even at twilight it's warmer than when you're imaging later.
My exposures were 360 secs at ISO 800. I did 20 lights, 15 darks and 15 flats and also bias shots at 1/4000. Not sure about the internal reflection - it seems to correspond in position to one of the black spots in the master flat.
Finally, does the master flat need to be changed to grayscale? As I mentioned, mine had a colour cast when viewed on the laptop in Images Plus.