Viewing a single comment thread. View all comments

Ignorhymus t1_ix9l66x wrote

Reply to comment by Grundyloop in How do astronomers share coordinates with each other? by vaterp

Do we need to know the time (noon, say)? Or the location (Greenwich? Equator?)? Or are they functions of each other?

3

nivlark t1_ix9ogvi wrote

The celestial coordinates are the same for everyone, by definition. But an individual observer must account for when and where on the Earth they are looking from to know where that point will be on the sky.

9

eatabean t1_ixc0hi3 wrote

Astronomers use sidereal time, which represents one revolution of the earth, roughly 23 h 56 min. No, a day is not 24 hours long. So we use coordinated AND siderial time.

2