I have an access to a remote telescope at 05.15-05.45 am at Hawaii time. The sun rises at 06.15 am. I will use this telescope for educational purposes for high school students. I wonder 30 mins is enough to make a variable star observation or a spectroscopic measurement.
The specs of the telescope could be found on https://lco.global/observatory/2m/
I would suggest a target which can only be observed before dawn with a large telescope: a faint comet just west of the Sun. Two candidates listed on The Sky Live are:
They are moving targets, currently about 2 arcseconds per minute of time. Pick one. To predict its coordinates for your observation slot, you'll need to get an ephemeris. Then if your images are successful, you can measure its actual position with astrometry software. Good data could be useful in refining its orbit.
If you're lucky, a stack of short exposures aligned on the comet nucleus might also make a pretty picture.
Alternatively you could try to get a light curve of an asteroid in the morning sky to estimate its rotation rate. Northolt Branch Observatories in the UK frequently post such results on social media.
I have been an amateur astronomer for over 60 years. In all that time I have not had more that a passing interest in variable star observation or spectroscopic measurements. What makes you think a bunch of high school kids will?
As I recall the best teachers I had were the ones that could make a subject interesting. Kid want candy. Give it to them. Point that monster at the most visually interesting objects. If you want to start a fire you use use a bit of kindling not a pail of cold water.
Put yourself in their position. A once in a lifetime opportunity and you want to turn it into a lecture on page 347 of the Science textbook.
