Re: moon transit fever

Jim Varney (
Thu, 16 Oct 1997 07:41:54 -0700 (PDT)

---Darwin Teague <> wrote:
> I have moon transit fever.... but I haven't had any luck yet. 
> Now I have lots of questions:
> 1. Can a sat that isn't sunlit be seen against an illuminated moon?

Theoretically, yes, but it won't be easy.  A 20-ft object at 700 miles
range only subtends 1 second of arc.  So I would select only the
largest objects at close range before trying.  I think there was some
discussion here a while ago about constrast effects and scattering,
which renders the black dot gray and makes it harder to see.  But
don't quote me on that.

> 2. Is there any time of the night or lunar month that is better to
> transits?

One transit observation doesn't make me an expert, but I sure liked
watching Mir go across the earthshine region of a young Moon.

There's a tradeoff with the elevation of the Moon.  If the Moon is low
in the west, there will be more transit opportunities due to the
apparent foreshortening of the orbital planes.  But the satellites
will be dimmer due to long range and poor phase angle.

All things considered I will try again with a young Moon for no other
reason than the brightness does not overwhelm you.

> 4. Any tips I haven't thought to ask about?

Use elsets that are very, very fresh.
Jim Varney   121.398W  38.458N 8m   Sacramento, CA,

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