Re: [ATM] Baffling Wynne corrector

[Polaraligned <polaraligned@optonline.net>]

>
> You can't change the 43mm spacing between focal plane and rear surface of
> last lens, but you can increase the distance from secondary mirror to 
> focal
> plane so that the corrector assembly is not quite so close to the inside
> edge of the secondary cage.  (Yes, you'll have a big secondary mirror to
> handle this situation without vignetting...but that's acceptable for 
> imaging
> at Newtonian focus.

I have already moved the corrector back 2.5" but because of the large
size of the focuser opening and large corrector lens, stray light still
has a clear shot at the first lens.  The diagonal is 6.5" as stands now.
I moved the whole focuser assembly back another 2.5" back from
the secondary cage and secondary becomes 7" tor provide a 2"
fully illuminated field.  No big deal with the 28% obstruction, but
having a SBIG camera hanging out on a 12.5" long focuser tube
seems a bit much.  Maybe it is ok with a stiff focuser.  I would
like to do the machining for this scope once and have no major
regrets.  I also had a folded design for this 25",  f/5 solid modeled
in Autocad, but because of this corrector, decided to try going with
a standard Newtonian set up.  I had great eyepiece baffling with
the folded design but as with the standard Newtonian design, the
insertion of the Wynne corrector scared me off of the design
because the first lens was not able to be "shielded" properly,
without a great increase in the CO.  The CO I had with the
folded Newt was 32% and the focal plane was 9" outside of the
tube assembly.  Secondary tilt was 20 degrees.
Do I really need to be able to have this corrector placed so
no stray "rays" of light hit it?  I don't mean by reflection, I mean
direct "rays".
Of course I want maximum contrast/performance, but where do
I make the compromise?
I really would like to go back to the folded design.




I don't have any webspace to post pictures.  I can maybe try PhotoBucket.


Thanks,
Scott








> Tom Krajci
> Cloudcroft, New Mexico
>
> PS.  A 25 inch scope for imaging?  What kind of beefy mount will you use?
>
>
>
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