Question

I was assigned something where I need to look at 1 star on 4 different nights and see what time it passes behind a tall object on earth to determine the length of the sidereal year. Would it be possible to do this in just one night? How much of a difference in time should there be from one night to the next in when the star passes it?

Answer 1

No, it is not possible to do in one night as you require at least 3 nights to get an idea of the time at which the star passes the tall object so that you can compare the time taken between 1&2, and 2&3 nights for the star to pass the object, which will give you an average value of a sidereal day which can be used to calculate the sidereal year.

Since, sidereal day = solar day - 4mins, therefore, there should be approx 23hrs 56mins difference between one and the next night.