"Henri Wilson" HW@.... wrote in message
...
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.

Yes but you also then get a very odd effect on the
spectrum which isn't seen either. The extinction
must always be much less than the critical distance.

George