So ships in Star Trek can travel many times the speed of light. So lets say they traveled to some arbitrary planter lets say, 300 light years away, and started construction on an enormous telescope pointed directly at earth. Would they be able to see 300 years into the past? If so it would be an interesting tool to study the history of the earth. Past mystery's could be solved, you could just mount one of these telescopes on a ship and it could fly to what ever range it desired.