Are you a tour tracker? Do you do virtual tours? Do you have a requirement for shooting twilight? If the answer to any of these questions is yes, then you need to look at the site I have referenced. http://stephentrainor.com/tools What is this site? If you are planning the day or week for photography and know that you are shooting twilight – it also works for sunrise twilights as well – then you need to download this free site.
By downloading this free site, you can type in any address that you might be photographing as well as the date of the photography. The software provids an overlay over Google Earth showing pathways of light for the three twilights – civil, nautical and astronomical – as well as list the times that the twilights begin. When you are looking at a 30 minute or less window, any advance planning you can get is very useful. By using this site, upon arrival we have pre-determined the best locations for our camera equipment as well as knowing if we have to provide flashes if we are staring into the sunlight. Give it a try- its free, its easy to use and it is a huge timesaver for you and your virtual tour company!