Re: TEC/TMB/AP eyepieces
- --- In email@example.com, "vahe352 <vahe@f...>" <vahe@f...>
> > Actually Vahe, the Zeiss Abbe orthos which Yuri preferred forratio
> > contrast were optimally designed for f/10 systems, but do not
> > suffer terribly with moderate departures from this system
> > requirement.
> The question is what is moderate departure. It is my understanding
> that the 1.25" Abbe's were initially intended for the Zeiss APQ
> series refractors, ranging from 4 to 6" in aperture and with F
> of f/6, f/8 and f/10. To me moderate departure is somewhere aroundimage
> f/8, below that you should see problems near the edge of the field.
> Of course since these babies are primarily intended for planetary
> work, and considering the planet's size as it appears in the
> eyepiece, once the planet is centered you should get acceptable
> from f/6 on up.ratio,
> My fastest scope is f/9 and Abbe's work just fine with that F
> in my f/20 scope if the planet is moved midway between the centerand
> the edge the image remains crisp and sharp, with the f/9 Abbe's doOrthos will add a little undercorrection to a fast null corrected
> not behave that well , does that tell you something?
lens. The amount of undercorrection is very small but there none the