I've had insomniac sleeping issues for a while now...
I find it helps to lower your stimulants at night
A few things I do each night before bed:
-watch less tv before you go to bed
-dont play computer games
-dont drink soft drinks,cups of coffe or tea
I also go for a bike ride every afternoon now straight after work for a bit of excersice.
I would say that staying up late at night to star gaze would higher your stimulants in your body though as is something that is exciting and gets the heart pumping... oh well
good luck, you should be fine once you know you have school the next day!