On Sun, 18 Feb 2007 15:29:52 -0000, "George Dishman"
wrote:


"Henri Wilson" HW@.... wrote in message
.. .
On Sat, 17 Feb 2007 20:00:07 +0000 (UTC), bz
...
So all double stars (with the right orbital plane) at great distances
should show large brightness variations.

Without unification they would, yes...but they don't...

Exactly.

Actually if the observer lies well beyoind the critical distance, no
brightness
variation is to be expected, even without unification.

I just noticed this in passing, that is not correct
Henry. Brightness variation still occurs but it
grows more slow as the speed difference decays. The
sum under an (inverse) exponential is finite, so
the distance in your program is actually the
integrated effect.

For the pulsar you are modelling for example, if
the area under the speed difference curve adds up
to the same as the initial difference time 8 light
years then the brightness curve will be as you
show here

http://www.users.bigpond.com/hewn/J1909-3744.jpg

even though we are 4000 light years away. In fact
that curve will apply for any Hipparcos distance
more than about 100 light years. In other words,
as long as the observer distance is much greater
than the extinction distance, the D in your program
is actually the latter.

THat is true. The distance required to match a curve IS the extinction distance
(or about 99.9999%)

No distances ever reash the critical one where multiple images appear....or
that's what appears to happen.

I was only pointing out that without extinction, stars at very great distances
should not appear to vary because the number of images should become very high.

I DID consider that this could explain many of the high frequency brightness
variations that are observed - even pulsars - but I dropped that idea.


HTH
George