Stuff already at Lagrangia?

Yes, that was my concern, thanks.

I just wasn't sure, given the angles, if there really is any available time
after dark when one could observe such an object before it would fall below
the horizon. But now that I think of it, it was probably a silly concern:
if we can see Venus in the evening, then we ought to be able to observe the
Earth-Sun Trojan points until even later in the evening. Sorry.

Ron Menich

cfrjlr@...
Please respond
to ssi_list

In a message dated Thu, 30 Aug 2001 11:29:11 AM Eastern Daylight Time,
rmenich@... writes:

>
> Eric Dahlstrom wrote,
>
> "
> I had looked into this as a possible Ph.D topic many moons ago. (I was
> thinking about infrared searches of Sun-Earth L4&L5.)
> "
>
> Eric: Are the Sun-Earth L4/L5 points observable in visible light from
the
> surface of the Earth?
>

Yes ( if I understand your question ).

It depends on your defintion of "observable".

They are always 60 degrees away from the sun in the sky, sitting on the
Ecliptic. So they can be above the horizon when the sky is dark, if that
is your concern.

Objects at L4/5 will not appear 100% illuminated, they will always have a
"gibbous" phase, that is about 66% of the hemisphere facing the Earth is
illuminated.

i.e. similar to the appearance of the Moon midway between full and first
(or last) quarter.