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From: Bill (no email)
Date: Thu Dec 08 2005 - 17:30:57 EST
>> Does anyone know the Apparent diameter of Venus viewed from the central USA
> On 2005-12-08 00:00 UT1
>
> Diameter 40.1"
> Phase Angle 117 deg (...meaning that less than half of the diameter
> is illuminated)
> Phase 0.27
George and Herbert
Thank you for your replies. Given the apparent size, and guess that only
26% of the right side is illuminated, it could make lunars with Venus very
interesting.
Herbert: Did you calculate your results, or is there a web site to look up
such information? It would look like the 0.26 phase may correspond to the
area illuminated?
I'm at a loss at how one derives illumination from the 117d figure. Any
help would be appreciated.
I also wonder, if like the moon, the line/arc between illuminated and dark
portions can be other than vertical. If so, where can one find/determine
that information?
OPTIONAL READING <G>
I did find that maximum eastern elongation was on Nov 3 2005 at 47d.
Inferior conjunction will occur on January 13. Using that I was a able to
roughly calculate the angle between earth, the sun, and Venus on the 6th.
Using 93,000,000 earth to sun, and 67,000,000 Venus to sun I calculated the
earth-Venus distance. Using 7521 as Venus diameter I calculated 38.5d as
apparent diameter. I am guesstimating about 25% of the surface was
illuminated. A long way to go ;-)
It was an interesting exercise. Once a had an estimate of Venus's daily
(earth day) angular velocity relative to earth, and earth's angular velocity
relative to the sun, I added the two and calculated Venus's velocity and
year length (in Earth days). Came up with 218.5 days, so close considering
I was playing slop pool.
Thanks again
bill
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