🚀 go-pugleaf

In article <2470@decwrl.UUCP> liss@psyche.DEC (Frederick R. Liss 237-3649) writes:

>                             ...  types of eyepieces. I'm not sure of the
>spelling or the exact names, but I believe they were the Orthoscopic (?)
>and Hyugens (?) eyepieces (correct me if I'm wrong) . Today I see adds
>for Nagler, Wide Field, Plossl, and Kelner eyepieces. 
>
>What I would like to know is how do all these eyepieces compare in price
>and performance. Which ones are suitable for high or low magnification,
>field of view, etc. I have also heard that some eyepieces work better
>with a refractor than with a reflector. What is your personal
>preference? My applications are observation of the Moon as well as the
>brighter clusters and nebulas. 

I am an amateur astronomer with moderate experience with deep-sky observing
(approximately 2500 different objects logged).  Most of my observing is with
a Celestron 14 (14-inch aperture Schmidt-Cassegrain, f/11), most of the rest
with six- and eight-inch f/5 Newtonians.

For deep-sky observing with the C-14 my favorite eyepieces, in order from
most-commonly used to least-commonly used, are

        55 mm Plossl (71X, University Optics, 2-inch barrel)
        12.4 mm Erfle (315X, Meade)
        32 mm Erfle (122X, University Optics, 2-inch barrel)
        20 mm Erfle (196X, Meade)

I use a low power for finding things and general viewing -- 71X is very
nearly a rich-field power on the big Celestron -- then occasionally switch
to more magnification to see detail, resolve stars, or cope with unusual
contrasts.  I have infrequently used 7mm and 4mm Orthoscopics to advantage
with this instrument, on close double stars.

I have sampled a variety of other eyepieces with this instrument in each of
these power ranges.  I advocate these more expensive eyepieces over cheaper
ones (Orthoscopics, Kellners, ...) because of wider apparant fields of view
and freedom from internal reflections.

Image quality is not too much an issue at f/11, except at the very edges
of the field.  Even an inexpensive coated Ramsden half-inch eyepiece
(Jaegers) gave superb definition near the center of its narrow field, and
was in that respect indistinguishable from the most expensive half-inch
eyepieces.  (Actually, it may have been slightly superior, because of
fewer air-glass interfaces.)

I personally have little use for the very-wide-field eyepieces such as the
82-degree apparant-field Naglers:  I find views through them momentarily
spectacular, but have difficulty keeping my eye sufficiently precisely
located to avoid obstructing portions of the field by parts of my own pupil.

With the f/5 Newtonians, my favorite eyepiece for deep-sky work is the
Meade 20mm Erfle mentioned above, closely followed by the best 4mm or 6mm
Orthoscopic I can get my hands on.

At f/5, image quality is everything!  You need the best eyepieces you can 
find (read "expensive") to work with a fast Newtonian.  NB:  Occasionally
a specific Kellner will work well with a specific Newtonian -- the 25mm
Kellners that Coulter ships with some of their Dobsons are often
satisfactory.

I have never seen a Barlow lens that was good for much at f/5.  Some of them
work pretty well at longer f numbers, but there you don't usually need them
since there are plenty of short-focal-length eyepieces that will do just as
well.

I have no financial interest, and no axes to grind, with any of the
companies mentioned.
-- 
Jay Reynolds Freeman (Schlumberger Palo Alto Research)(canonical disclaimer)