On 28 Mar 2007 02:16:59 -0700, "George Dishman"
wrote:

On 28 Mar, 08:10, HW@....(Henri Wilson) wrote:
On Sun, 25 Mar 2007 23:34:03 +0100, "George Dishman" wrote:
"Henri Wilson" HW@.... wrote in message

George, when you can, have a look at

http://www.users.bigpond.com/hewn/ellip_circle.jpg

This shows how an elliptical orbit can produce a near perfect sine wave under
certain condition whilst the circular orbit produces nothing like one for
exactly the same parameter values.

Yaw angle is -90 (periastron closest to observer).

The white curve is an exact sinewave.

You might like to consider how the elliptical orbit's
curve will change with distance.

For small changes in magnitude I cannot tell the difference between the output
for a circular orbit and one with a small eccentricity.

The shape of the 'sinewave' produced for an elliptical orbit certainly changes
with distance, as expected. However it is certainly interseting to note that a
perfect sine wave 'bunching curve' can be produced by a star in an elliptical
orbit.

There is probably an algebraic reason for this ...but I don't think I'll bother
to find out what it is.

For example can you
do the same at a distance where VDoppler and ADoppler
are of equat magnitude (the 45 degree case for a
circular orbit).

George, I think what you are calling VDoppler is what you would get if you
placed a large number of equally spaced lights around a spinning wheel (Edge
on). Those on the sides would be 'VDoppler bunched' or separated.
This is not the situation we are examining. The pulses are emitted in sequence
and not all at the same instant..and not at exactly the same point.

In recent measages you seem to have been switching
between saying VDoppler doesn't exist at all and saying
it exists but is negligible presumably because it is
much smaller than ADoppler.

I have finally realised there is no VDoppler in the classical sense (as in the
case of the spinning wheel, above)

What the program measures is the rate at which pulses arrive. The ones on the
edge are emitted under constant velocity conditions and arrive at *very nearly*
the rate at which they are emitted. There is a very small difference due to the
fact that consecutive pulses are not emitted at the same point. I have
incorporated that by adding an Rsin(x) term to the star distance. It is
generally negligible.

I have held off replying to
see if you would clarify that (and also I was out last
night and we had visitors at the weekend). I've also
been tinkering with a GUI and might do a simulation for
comparison with yours but I have a couple of other
projects I'm working on too so I may not spend too much
time duplicating what you've already done. Does your
program actually include VDoppler or not?

George, I think your model is something like a spinning wheel with many lights
equally spaced around its rim. VDoppler shift will occur in that model, if you
assume constant light speed to the observer from all sources. The correct model
is a spinning wheel that has one *flashing* light on its rim. There is a subtle
difference. Conventional VDoppler does not occur in this case.
The shift in the former is (c+v)/c. In the latter it is something like
(D-Rsin(xt))/D and very soon disappears.

Do you see what I'm getting at?

George


"When a true genius appears in the world, you may know
him by this sign, that the dunces are all in confederacy against him."
--Jonathan Swift.