What to observe with a remote telescope close to sunrise time? 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 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.