Thank you. I missed it too. And just today I was asking technical information from a questar (3.5" telescope) group member about some technical aspects of star shots. I think this just answered them for me. But one more question of you: Does i only take 5 seconds to get small star trails? I have been dealing with coma from various lenses, but now use a D500 at ISO of 4000, which gives me exposures of less than 5 seconds even with f4 opening.