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frbee
2009-Jul-02, 10:23 PM
so the stars on the Meridian at midnight would have a Right Ascension value of about how many hours away from the Right Ascension of the Sun?

can someone answer this and then explain?

thoth II
2009-Jul-02, 10:34 PM
so the stars on the Meridian at midnight would have a Right Ascension value of about how many hours away from the Right Ascension of the Sun?

can someone answer this and then explain?

RA is angle measured eastward from vernal equinox in hours 0-24 hrs. The sun's RA can be looked up for today's date (the sun starts with RA = 0 at vernal equinox and increases by 2 hr/month after that) .

The stars on meridian would be approx. = RA(sun) + 12 hr.

(because at midnight, the sun is 180 degrees = 12 hr. around from the meridian).

frbee
2009-Jul-02, 10:36 PM
then it is 12 hours away?

thoth II
2009-Jul-02, 10:38 PM
then it is 12 hours away?

yes, it is 12 hrs. away

frbee
2009-Jul-03, 04:24 AM
thanks thoth.

Amber Robot
2009-Jul-03, 04:25 AM
Now he can score that 100% on his quiz! ;)