Sky Watching

Rocky loves watching the stars of the night sky. He has a telescope with a range length $L$ whose stand is damaged in such a way that you can’t move the telescope up, down, left or right. It can point only to a fixed point in the sky. Rocky likes to watch as many stars as possible. So, he got an idea and made a slider for the base of the stand. But the slider was too slippery, so you have to fix t