Have you ever tried the Pentax line of eyepieces? Eyepieces can be made
parfocal over a wide range of magnification. Tom Noe, who builds the
Teleport dob, recommends Pentax for just this reason. BTW, Al Nagler
used to tout the "Nagler" line of eyepieces as being optimized for 18"
f/4.5 dobs--guess who makes, by far, the largest number of these?? You
are correct now, however, there is no such thing anymore as the "Nagler"
series.

The Televue web site has a chart giving the parfocality characteristics
of the various eyepieces--wonder why the new 31mm is not in the chart
since it might take, perhaps, 5 minutes to add the entry?? And, the 31mm
has precipitated a redesign of the Paracorr coma corrector by Nagler. It
may all be worth it--I'm anxious to try my 31mm in the 10" LX.

>
> >From what I've heard, those scopes are really great, but perhaps they are
> just a little too narrowly optimized in their design to assume that
> accessories which will work on most scopes, will work on them.
>
> So in that sense, I think the real cause of the problem is either in scope
> design/selection/configuration or eyepiece selection, not the eyepiece-design
> end.
>
> I don't view "Naglers" as one line of eyepieces. That's why they have
> different names: Nagler, Nagler Type 2, Nagler Type 4, and Nagler Type 5.
> You can't expect the guy to change his name every time he designs an
> eyepiece. He already did us the courtesy of distinguishing between the types
> by numbering them.

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