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"Big Plossls" - Televue 55mm, Meade 4000 56mm (4-Element Design), Meade 4000 56mm (5-Element Design)
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Certainly a “novelty” eyepiece in many respects by today’s standards with so many fast scopes on the market as a 55mm eyepiece produces a rather large exit pupil, these eyepieces are still very practical for longer focal ratio scopes which are f/8 and slower. Of the three used in this quick look I did early in 2009, both the TeleVue and the Meade 4000 4-Element are still currently available and manufactured in China. The particular version used here was a slightly older one manufactured in Japan. The older Meade 4000 5-Element (pseudo-Masuyama design) is long out of production.
quick comparison was conducted using all of these eyepieces in a
TSA-102 f/8 APO, a Celestron C-6 f/10 SCT, and to challenge the
off-axis performance, an Orion XT10 10” f/4.7 Dob. While the
exit pupil produced by these eyepieces would be just under 7mm for
the refractor and SCT, for the Dob it would be a huge 11.6mm! This
of course would mean a much dimmer image than I would be used to with
the Dob as so much of the light would be blocked by the smaller 6mm
to 7mm opening of my eye’s iris when fully dark adapted, but
still it would be interesting to see how the edge correction would be
for the giant Plossls in such a fast scope.
56mm Meade 4000 Plossl(5-Element Design)
55mm TeleVue Plossl
56mm Meade 4000 Plossl(4-Element Design)
Details of the Results
#1 and #2 were very close. In both, the edge correction was equal in
my XT10 f/4.7 Dob and I'd say a slight edge went to the TeleVue in
terms of beings able to pull in the very difficult to see faintest
stars (which can be due to more than just transmission, as things
like scatter, spot size, chromatic aberration, distortion, etc. can
all contribute to the ability to see the faintest stars). While I
could still see the faintest of stars being observed in both of these
contenders, the faintest stars seemed a little stronger looking in
the TeleVue. However, the Meade 4000 5-Element showed a slight edge
over TeleVue in terms of star colors or color saturation, and how
much "presence" or "authority" the stars
conveyed. So when I was observing clusters with any of the
telescopes, the brighter stars seemed to pop out more in the Meade
4000 5-Element vs. the TeleVue, resulting in a little more of a
dimensional impression to the view. Finally, the Meade 4000
5-Element took a square win in the "engaging" department.
Eye placement was much easier than with the TeleVue, and I always
felt more engaged and observation seemed more comfortable and natural
without distractions when viewing with the Meade 4000 5-Element
Plossl vs the TeleVue. So in the end, while both were really close,
I felt the Meade 4000 5-Element gave a little stronger visual
experience overall than the Televue, which earned it its Rank of #1.
The Meade 4000 4-Element Plossl was also quite a good performer, even compared to the much more expensive TeleVue. The bottom line is that it did produce a beautiful picture, worked very well, and felt it was an excellent value for the money. Where it trailed the other two was the view of star fields had slightly less “pop” and edge correction was also slightly less controlled.
If I were going to use this class of Plossl often, then for the $100 or so more for the TeleVue Plossl at $190-$219 new vs the Meade 4000 4-Element Plossl at $75-$89 new, I would say it might just be worth the extra investment as one gains a little more “pop” and dimensionality in star fields, edge correction is slightly better, and dimmest stars are easier to discern. If on the other hand a 55mm Plossl is only going to be an occasional use item for you such as a less often needed 2” max True Field of View (TFOV) finder eyepiece, then I feel I’d definitely go for the Meade 4000 4-Element Plossl as you are probably getting 85%-90% of the performance of the TeleVue. If you are a collector and want the best possible, out of the three in my opinion the older Meade 4000 5-Element Plossl would be something I’d be keeping my eye out for on the used market as it is a real gem both in performance, look, feel, and build.
As a side note, while eye relief is long on all these eyepieces (38mm for the TeleVue), my preference seemed to be for the no eye cup or eye guard configuration of the Meade 4000 5-Element. However, while the TeleVue does have the long cone-shaped upper housing which is used in part as an extended eye guard as it is entirely above the eye lens, I discovered that this portion does simply unscrew so the Televue can become an eye guard-less version similar to the Meade 4000 5-Element.
though, these Big Plossls are wonderful eyepieces in longer focal
length instruments. As example, in both my TSA-102 (3.2 deg TFOV)
and Celestron C-6 SCT (1.7 degrees TFOV) the views of the M42 Orion
Nebula and the Pleiades was nothing short of mesmerizing. And even
though the Apparent Field of View is only 50 degrees for these 2”
eyepieces, they still gave somewhat of an impression of the
wide-field experience plus a rare level of comfort with their very
large eye lenses.