vignetting on a C11

So I picked up a nice NS11. Thanks again for everyone's help in my earlier post to help make a decision. Upon examination of it I noticed a pretty small opening with the stock visual back. I checked and Peterson doesn't show an eye opener for the this scope. Is vignetting an issue with 2" long f.l. eyepieces? If so, at what f.l. does the vignetting start?

Thanks in advance,
DanL

Hi Dan

This AP part-- "2" Adapter with Brass Locking Ring and 3 Large Thumbscrews - for larger SCTs with 3.25" Rear Cell, (ADASCTLC and ADASCTLM)

Near the bottom of this page--

http://www.astro-physics.com/index.htm?products/telescopes/160edf/160edf

It seems popular, and I like mine on a CPC1100. I use it usually with an ordinary refractor-style dielectric diagonal. It is very heavy duty and well-made.

Looking thru the AP adapter into the SCT back-baffle, the back-baffle is 'very near' 2" aperture (slightly conical). So this AP adapter preserves a 2" opening all the way back to the diagonal. Of course the aperture would be slightly smaller inside the diagonal.

Dan Lamoreaux said:

So I picked up a nice NS11. Thanks again for everyone's help in my earlier post to help make a decision. Upon examination of it I noticed a pretty small opening with the stock visual back. I checked and Peterson doesn't show an eye opener for the this scope. Is vignetting an issue with 2" long f.l. eyepieces? If so, at what f.l. does the vignetting start?

Thanks in advance,
DanL

I've got an Eye Opener for my 11(Petersen used to make them for the Celestrons)...it is A VERY nice piece of work, but, frankly, I have never noticed a difference with/without with oculars up to and including the 35 Pan. The only benefit to these things for visual use (including the AP one) IMHO is that they allow you to insert a 2-inch refractor style diagonal into the scope without the use of a 2-inch adapter. If that doesn't sound fun enough to you, save your money. :-)

There is the new option on the market - CLSCL-2 = 2" Clicklock Eyepiece Clamp for Large SCTs, 3.25" Thread from Baader.
http://alpineastro.com/eyepiece_adapters/eyepiece_adapters.htm#2inch%20Clicklock%20Eyepiece%20Clamp