Is f/3.7 workable with a Newt?

[Kaptain Klevtsov]

Just been looking at E-bay (as you do) and noticed some Phenix Newts on there. The 200mm f/3.7 one caught my eye, as it's got a parabolic mirror, and (allegedly 1/10th wave) is rather fast. This is a good thing for imaging, but it's by far the fastest Newt. I've ever come across. Would it work well, theoretically I mean initially, or is it likely to have "issues" for imaging?

Just out of interest you understand.

Captain Chaos

[GazOC]

Large, premium (24" +) amatuer Dobs are frequently made to f3 - f3.5. I expect you'd need a paracoor to help with the coma, but it's def. 'doable'

[Kaptain Klevtsov]

Thanks for the input Phyllis, it's nice to get info from somebody who knows their stuff. I'm not buying one of these (yet), it just intrigued me that such a fast Newt. was out there in the marketplace. It could be the next big thing, or it could be plagued by coma all over the FOV. I suppose I'll have to wait until somebody grabs one and reviews it.

Captain Chaos

[GazOC]

Don't mention it.

[GordonCopestake]

I think the reason schmit newts (at f/4) have corrector plates is to reduce the stress on the mirror maker. The amount of coma these things show might not make it worth it, even with a paracor. I would look at the meade SN's instead, as at least they have some sort of built in correction. Oh and not to put to fine a point on it Phenix stuff in my mind is right up there with seben...

[Kaptain Klevtsov]

Sorry Gaz, didn't mean to imply that you don't know your stuff. Should have been more careful.

Gordon, I know what you mean and wasn't going to buy one.

I was just interested as I've read that some eyepieces struggle to perform in a fast (f/4 to f/6) Newt. What happens at f/3.7 is what interested me, especially when you add a focal reducer.

Captain Chaos

[GazOC]

Just kidding mate!