I try to go for 900 frames on not so good nights and 600 frames on above average nights and 450 frames for those gobsmacking 3 times a year nights. That's 90sec at 15 fps, 10 fps and 5 fps.
Though there has been talk recently of stretching the 90 sec to 120. Don't know if the "professionals" around here have had the sky or the heart to try it yet
