Went out to the hills to do some star shooting, and this one my favorite picture that i got
used the rule of 400 for this, which is 400/mm that your lens is at.
Mine was at 18, so 400/18 is about 20. So my exposure was 20 seconds.
This rule allows you to not get visible star trails in your pictures.
The tutorial that i used for it is here... www.diyphotography.net/photographing-stars-at-night-video...
I also used my DIY shutter release for this
20sec | f/4 | ISO500