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...
Under clear, dark pre-dawn skies, look to the eastern horizon half an hour before twilight begins to show, from about October 14 through to around October 28. Content continues belowThe best mornings to see this phenomenon are likely around October 15-17, ...
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...
Red rainbows can be observed espe- cially at the time of twilight when red-coloured light from the sun gets refracted by waterdrops. The "rain" imme- diately before this phenomenon might have supplied the waterdrops to cause rainbows in the quite dry weather in Babylonia. Nevertheless, we ...