Also due to atmospheric conditions, too long of exposure can lead to bluring, sometimes it pays to do a bunch of shorter exposures and stack them, also trying to use a long lens to fill the frame can have problems due to the minimum f-stop of the lens and the lens’s ability to magnify atmosperics, sometimes using a shorter faster lens, even though you don’t fill the frame can result it better images, you have alot of megapixels to play with even on a quarter screen.