You are always better to under expose than over expose. Over exposure can/will blow the stars out. Usually resulting in Halos around the bright stars. Next to impossible to fix in post.
You have the start of trailing on this (/) angle. I might try 300 sec exposures OR you'll have to improve your guiding RMS. May be a PA issue also.
You have the start of trailing on this (/) angle. I might try 300 sec exposures OR you'll have to improve your guiding RMS. May be a PA issue also.