Quote:
Originally Posted by Meade bloke
Ok I'm new on this forum ??? .But why would you not set it to your own timezone ?  a pointless exercise otherwise, or am I missing something??...
Cheers
Spud
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Wow... sometimes the simplest questions have the biggest answers!
Local time is fine for most things at a local level, however, when you start comparing, say, an image of Jupiter taken in Australia and an image of Juptier taken from North America, local time gets a bit messy since everytime you make such a comparison, you have to do the time conversion and hope you get it right. So to simplify things, astronomers often work in Universal Time so no matter where you are on the globe, if you make an observation at 20:53UT and someone else makes an observation at say 21:00UT, the relative time difference is easy to work out, and easy to check. So the conversion to UT is done once by the observer and not many times by lots of different people... It probably gets even more important with predictions, since often predictions are made not knowing the observer's location. So, for example, a prediction could be made that an astronomical event will occurs at say 22:30UT. That would be a different local time for you and for someone else on the other side of the globe, but it's simple to convert UT to your local time.
Sidereal time is really a way of keeping track of what is visible in the sky(apart from the sun) at a given time. It is the right ascension of the meridian that is at zenith at any given time.
Hope that helps... if it doesn't, ask again! If I can't explain it some one will!
Al.