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Posted: Sat Feb 09, 2019 10:46 am
when I use brain to calculate exposure, have to take only a portion (how big?) or include the whole frame?
I also think that if you make measurements at the beginning of the evening it will surely change overnight.
Posted: Sat Feb 09, 2019 10:07 pm
I have only used it a few times but just selected an area a few 100 pixels square trying to avoid any nebulosity and concentrations of stars not sure if that is correct or not but appeared to work. I use a monochrome camera so have to resample for each filter anyway. But theoretically as the night goes on the conditions would change as would the orientation of the scope + any localised light pollution sources so assume it would be prudent to recheck. Although if it is going to change the gain / exposure it will make flats and darks etc a bit of a pain in the rear, I am sure Robin will be able to be more specific.
Posted: Sun Feb 10, 2019 8:34 pm
When measuring the sky background you can select a fairly small area of sky to try and avoid nebulous at the or bright clusters of stars. A square area may be a hundred pixels on the side would be quite big enough.
Hope this helps, Robin
Posted: Mon Feb 11, 2019 10:59 am
thank you. I'll try tonight.
still have to go crazy even for focusing.