Revised 10/97- The entire PANOPTIC line!
In this edition of "Equipment Talk" I will go over all the Televue Panoptic Eyepieces from
15 mm focal length on up. All information offered here is from personal experience only,
there may be some unintentional errors or omission of facts.
The Televue Panoptic eyepieces are the natural extension of the Nagler line.
The Naglers run up to 20mm in focal length, and offer an 82 degree
apparent field, while the Panoptics start at 15mm f.l., and run up through 35mm, offering 68 degrees of apparent
field size. The Panoptics feature very sharp images across almost the entire field in most scopes. I have tested
them in a variety of scopes from 43mm to 16 inches. From f/3.1 to f/15.
I will discuss their pros and cons as we run down each eyepiece below:
The 15mm Panoptic: A truly sharp-to-the-edge eyepiece, yet the 15mm is
sometimes considered the least impressive of the Panoptic line. This is perhaps
unfair. The 10mm eye relief is shorter than it's big brothers, so some observers
complain about it. In reality, it is very hard to find ANY eyepiece at 15mm which
offers much more than 10mm eye relief anyway. (with the exception of specialty
eye-relief eyepieces such as the Vixen Lanthanum, which has 20mm eye relief at
15mm focal length, and the Pentax XLs - see other article) Also, the 1.25" eyepiece
is so small and convenient, that many folks will think they simply look less expensive...
or less like a "Panoptic". In truth, this is a great eyepiece, with eye relief that is a too short for
those who wear or need glasses at 15mm (you tend to need to correct astigmatism as you use lower
powers, not higher ones, so you may be able to get away with this one w/o glasses,
just correcting for your diopter with focus) The only problem I perceived with this
eyepiece, is that the many elements may soak up a tad more light than those with
fewer elements, but is makes little difference in most uses. All Panoptics exhibit pin-cushion
distortion, which apparently is part of the reason they are so sharp (see below).
The 15mm does make a good planetary eyepiece. I have found a few other eyepieces to
surpass the panoptic on contrast in planetary performance, including the Naglers, however.
This eyepiece works well with all bino-viewers, by the way. The eyepiece does have an easy
to use fold down eyeguard.
The 19mm Panoptic: This is one of the best eyepieces you will find period. It is a relatively small,
lightweight, 1.25" eyepiece that came out in the Fall of 1996. It can be used in binoviewers easily.
Views were sharp to the edge of some scopes, and almost to the edge in others, with more coma
noted on very fast scopes hurting edge performance. The Televue's Parracorr cleans that up in
a snap. The price is high for this focal length, but I would recommend this eyepiece highly, as THE eyepiece you
should have. It works well with a regular 1.25" barlow too,with no vignetting noted. The size makes this eyepiece
superior to the 22mm Panoptic for many users. Eye relief on the 19mm is good, with maybe 50% of all glasses
wearers comfortable with it.
The 22mm Panoptic: Billed as the alternative to the 20mm Nagler, indeed this eyepiece
may be even more desirable. It is a 1.25" eyepiece with a 2" skirt, and is larger than a
9mm Nagler, but smaller than a 12, or 16mm Nagler, to give you an idea of size. It is
MUCH lighter than a 20mm Nagler. Still it is pretty hefty for a bino-viewer, and also, due to
it's wonderfully large apparent field size, can only be used in those with wide clear aperture
such as the Televue bino-viewer. (More on bino-viewers in a my other article..do not buy them
without thorough research!) The eyepiece affords a generous eye relief, approximately 18mm or so (personal
estimate), just enough for most (but not all) eyeglass wearers.
More on the 22mm Panoptic..
Now, about the view! Wow! A wide field, that approaches the actual field of view of the
20mm Nagler in actual use. (If you bury your head in the 20 Nagler, and really look around ,
you can make out significantly more field..but in practical use, the 22mm Panoptic has about
the same "easy-to-see" field size) Correction towards the edges on mid-slow scopes f/6 and slower,
was excellent. (although NOT perfect) In fact, the eyepiece was color free, and distortion
free towards the edge, especially when compared with a Meade 24.5 superwide,
one of it's closest (but less expensive) competitors. (alsoan excellent eyepiece)
Also.. the view seems less tunnel-like for some reason in the Panoptic,even though
the true field of view is about the same. However, note that the the Meade eyepiece
is pure 1.25", not a hybrid, and you may find that it works better in some binoviewers, than
the 22mm Panoptic. The Panoptic will work in binoviewers, but is a bit heavy. I suggest the 19
for them.
The 27mm Panoptic: The single sharpest eyepiece low power eyepiece I have ever used,
the 27mm is a true 2" eyepiece, and needs a 2" diagonal, or focuser to hold it.
However, it is not much bigger, or heavier than the 22mm Panoptic. Pinpoint images over a huge
field of view for this focal length make this a winner. Everything was sharp and bright to
the edge at f/8 and higher, with some coma noted at f/4.6, but not a lot. This one really "wows"
compared to the very nice, but not quite as fantastic 24.5 Superwide.(Meade)
The field of view on this eyepiece is wider than 1.25" 40mm eyepieces, and yet the
magnification is much greater. I cannot express into words, how perfect the view through this
eyepiece is in a 5" Apochromatic refractor. It's a marriage made in the heavons.
The 35mm Panoptic: A most useful eyepiece because of the wide true field,
a combination of low focal length, and it's own wide 68 degree apparent field.
In some scopes, star images are not quite pinpoint, and the reason seems to be from the
user and the scope, but NOT the eyepiece itself. Televue discussed this with me. The user
will find that as the focal length goes up (such as in the 27, and 35mm) the "exit pupil" gets
larger, and the user's minor astigmatism will show up. You may not even know you have
astigmatism, but it will be evident in this, and other low focal length eyepieces when you are
observing (The tip off is that you cannot get the star to a pinpoint, it is first too long in one direction,
then too long in the other direction.. if you turn your head sideways, the orientation of the distortion
will change, confirming your astigmatism). Also, fast scopes will have significant coma problems
with this focal length, and field size. The Televue Parracorr is a must. The GREAT news is that
scopes that suffer from curvature of field such as Schmidt Cassegrains, usually have trouble
with low power, wide field eyepieces, such as the Meade 40mm Superwide.
I hate seeing sea-gulls towards the edge. The bottom line is that if you have a fast scope, (lower than f/6)
you might do better with the 27, unless you use the Parracorr..
More on the 35mm Panoptic..
Like all the eyepieces above, the 35mm can be sent in for repair to Televue after you
use it a lot..and believe me you will use this eyepiece a lot.. giving you the widest possible
field (almost) that can be had in a 2" eyepiece. In fact, the true field of view, is just short
of the 2" 55mm Televue Plossl, and 2" 56mm Meade Super Plossl in terms of size. Eye relief
is comfortable, for this focal length, it isn't "too much" as you often see in 32mm and up plossls
of 1.25" design. I can use the 35mm and the 27mm eyepiece with glasses, with just slight crowding.
Pin Cushion Distortion:
The only problem with Panoptic eyepieces is something called "pin-cushion"
distortion. If you have a Dob, for instance, and love to pan around the sky, the starfield is magnified
slightly more towards the edges. In fact, in looking at a ruler, even while stationary through the
eyepiece, the ruler looks bent.. it's sharp, but the trade-off is a distortion that bends straight lines.
When panning, this can literally get you sea-sick. The distortion is very minor to some folks, and
bothers other's more. Most people have not noticed it that I have spoken to..but those that Pan
around a lot certainly do, and it is very noticeable in daylight. The distortion is correcting the
performance near the edge of field though, which is the goal.
Barlowing Panoptics:
I will talk a bit about barlowing the Panoptics at this point. On all telescopes I have tested,
I have been able to barlow the 22, 19,and the 15mm Panoptics without any problem using a 1.25"
or a 2" barlow of good quality. The 27, and 35mm Panoptics need a 2" barlow, such as
Televue's Big Barlow. I have not really noticed the necessity on the scopes I have tried,
for the Televue Panoptic-Barlow interface. This is recommended though by Televue, when
you barlow the 27mm, and especially the 35mm. This additional interface will correct some
minor vignetting that occurs because of the way the light rays are bent in the barlow.
It helps to bring all the light to the eyepiece. In a separate issue, I have noticed some
Kidney Bean black-out areas when barlowing the 35mm.
SUMMARY:
In summary, the Televue Panoptics offer some of the best, sharpest views available, at medium
to low power, along with a wide field of view. Stars and planetary images are very sharp. Eye
relief is for the most part comfortable, and light throughput is acceptable. Some scopes will
do better with the 35mm than others, and also the view barlowed reportedly varies with scope.
If you had to choose only one, I would pick the 27mm Panoptic. In fact, if you get crafty with
a barlow and place it at different distances from the eyepiece, you can theoretically use just
this ONE eyepiece, and get away with it.. but now I am starting to drift onto another
topic altogether!
The Pentax XL series offers a real challenge, especially to the 15mm of the Panoptic line, read my subsequent
article for info on that!
Clear Skies!