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Observing Project

  1. Feb 3, 2010 #1
    I've been asked by my astrophysics lecture to conduct an observing project of Bright Stars, using the time at which they transit the meridian to locate them on the sky. I was just wondering if you could check my "thoughts" so far?

    The Hour Angle of a star is 0 at the time it crosses the meridian, so my LST will be equal to the stars right ascension? So GST will be RAStar + my Longitude?

    Now, am I right in thinking that GST would be also equal to the GHA and RA of the sun on that day? So using Universal Time = GHASun -[tex]\xi[/tex] + 12hrs, I can sub in my known RASun, longitude and RAStar in place of GHASun?

    Is this remotely correct? I tried to calculate a value, and ran it through using http://www.stellarium.org/" [Broken], but it seemed completely wrong.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 5, 2010 #2


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    Why would this be true? The position of the Sun has nothing to do with sidereal time. Since you're trying to find the right ascension of stars in the first place, why not time the transit of the vernal point? Right now, Aries is easily visible in mid-latitudes after sunset.
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