Re: [ATM] Ghosts in the Coulter

["Jerry" <wa4guu@verizon.net>]

Yep! The problem is what could cause multiple images to be formed close to
the proper image at the focal plane. If they are nearly focused and show the
cresent shape of Venus and nearly the same size, as was the depiction, then
the ghosts are somehow split from the light cone from the primary on the way
to the focal plane. Something of a specular nature is splitting off the
spurious images at multiple small angles. There is only so much stuff of a
specular nature between the primary and the focal plane.

To offer another possible explanation...I think I offered it before but with
the idea that there was only one ghost.

Multiple holes in the aluminum coating of the secondary allowing multiple
reflections off of the back surface. The holes would have to be large enough
for the reflected beam to come back through to the eyepiece. Or there would
have to be a larger number of small holes to allow a path into the glass and
another hole to let it out to the. More likely numerous holes or one big one
letting light to the back surface and numerous smaller holes letting it out.

It would be interesting to know if the spurious images can be brought to
good focus and if so, how much rack and in which direction.

Jerry 

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Vladimir Galogaza
Sent: Monday, May 21, 2007 3:39 PM
To: ATM List
Subject: Re: [ATM] Ghosts in the Coulter

Brian,

>Temperature causing warping of mirrors/mounts?

This is very general statement. We usually want detailed explanation.
Stephen mentioned that
several sharply defined ghosts can not be easily, if at all,
explained by  warping of the mirror. He even simulated
the problem by reversing it. He postulated
finished image with ghosts and calculated what kind of
warping can cause it. His result (and my intuition)
tells me that it will be very elaborate warping required for this.
Not very likely in real mirror(s).
Various usual aberrations cause image distortions  but not multiple
well defined images of very different intensities.
This is why I was asking for ghost photos (with no response?).
If mirror cooling will remove ghosts, than ghosts should disapear
gradualy and continuosly. Following  and describing in details the behaviour

of
ghosts during cooling time will bring more light to what is possible cause.
Instead we have only this:
>"I opened the tube for another 30 minutes and the ghost went away."

Regards
Vladimir.


Regards
Vladimir

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