Ever since I saw the first post on this here, I've wondered about automating this to some degree of accuracy. Contrast recognition on the skyline/cityscape imag

Ever since I saw the first post on this here, I've wondered about automating this to some degree of accuracy. Contrast recognition on the skyline/cityscape image to delete the light-polluted sky I can't imagine would be too hard, a bit of math could tell you where in the world this sky would be in the next few hours to filter an image database search (provided the images had location and time data), and combining the two would be relatively simple. The biggest part I can't get around is maintaining the shot angle so it's EXACTLY the same sky. The image database, too, would have to be pretty extensive.