The horizon is indicated by the boundary of blue and red; in the left part the day-break (AVRORA) with a rising border (ORTVS), in the right part the twilight (CREPVSCVLVM) with a setting border (OCCASVS). The dark circle at the bottom displays the astronomical night. Three pointers...
As you can see, the gold standard for astrophotography, a twilight flat, is not very representative of a dark night, having WAY too much near infrared light. What is also interesting is that my dark sky spectrum has changed considerably from 11 years ago. Figure Three shows a sky backgroun...