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Re: [APML] Coma Corrector for 10" f/4.72 Newton

Title:
Walter,

No it is not vignet free. If you look at the bottom pic, you will see in the corners that it is darker. Don't look at the band across the top, that was caused by the camera body I used. If I remember correctly, I could have gotten full coverage but due to my incorrect designing, I made that impossible without a new tube and focuser. My focuser distance to secondary (if I'm remembering correctly) ended up giving me the vignetting, which there should have been none according to my plans, but as pieces I'd ordered came in, placement of the secondary and distance from it to film plane caused me problems.

hope this helps,

Scott B.

Walter Koprolin wrote:
Hi Scott!

  
First off, does your scope give you a full frame with no vignetting now?
    
I am designing my telescope (which does not exist yet) for no vignetting,
which should be achieved with a 3.5" secondary and a 12" tube, and a 2.7"
focuser.

  
I'd sure be willing to work something out with
you on the paracorr.
This is a link to the test pic I shot to test the scope and paracorr.
The top image is the one with the paracorr and you can see that it does
increase the magnification just a bit, so would increase your T stop a
bit also. These pics are raw scans, and were taken with a 30# 14" tube
on my G-11 in a 20 mph wind, so you may notice some movement but not too
bad. You can really see the coma in the bottom photo in the left/left
bottom of the lower pic. By the way, don't try and search around the
site, I haven't gotten around to working on it in the last year. :o(

http://www.geocities.com/cloudchaser57/astropics/paracorr_comparison.jpg

hope this helps!
    
Thank you for the comparison, which is interesting. It cleary shows coma
correction and the additional magnification of the TeleVue Paracorr, but
it also shows to me that the Paracorr does introduce some additional
vignetting (it has only a free aperture of 38mm, if I remember correctly).

Yours sincerely,

  Walter Koprolin
  Astrophoto-Gallery, Observation Reports, Telescope Testing:
  http://www.astro.univie.ac.at/~koprolin/


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