More Stuff About Eyepieces
Update: Since this article was originally written, some of the eyepieces referred-to have been superceded by newer models. However, these older eyepieces often appear in the used marketplace.
In any discussion of eyepieces, one thing comes out clearly: everyone has their preferences. Sometimes the differences between various eyepiece designs and/or brands are obvious. But quite often it's hard to see any difference at all. Faced with a bewildering number of choices, it's helpful to find out a little more about what's on the market these days.
After the March 2001 article on Tele Vue Nagler eyepieces, there was a question about the difference between the Meade Ultra Wide Angle (UWA) eyepieces versus the comparable Naglers. Meade advertises an 84o apparent field of view (FOV) while the Naglers claim 82o. I did some research via the Internet and came up with a few details from sources that seem to have reliable info. The Meade UWA eyepieces are essentially a knockoff of the original Nagler design which, curiously, was never patented. Al Nagler has since patented all his newer versions. (The Meade Super Wide Angle is also a clone of the old Tele Vue Wide Field eyepiece.) Meade's claim of two extra degrees in FOV is simply an advertising ploy to upstage the Nagler; in fact, neither the Nagler nor Meade UWA give exactly their advertised apparent FOV in all focal lengths. A recent study showed that quite often various brands advertise a field of view that is a few degrees greater than the actual measured apparent FOV. However, you'd probably never notice such a small difference.
Back to the original question: which is better - a Meade UWA or a Nagler? I've had a Meade UWA for twelve years and have been very happy with its performance. It truly has a wide field that is sharp right to the edge. However, it does have a considerable amount of internal light scatter, which plagues many wide field eyepieces. In the intervening years, Tele Vue has brought out new versions of its designs which correct some of the problems inherent in wide field eyepieces, while the Meade UWA is basically unchanged from the original that was first sold in the mid-1980s. Reports from users also indicate that Meade doesn't do as good a job of interior blackening and baffling, which worsens the light scatter. Today the Naglers are probably a better choice, despite their higher cost.
Most everyone who has viewed through one of the very wide field eyepieces is amazed at the expansive views they provide. It's not difficult to make an ocular with such a wide field; the trick is to make one that doesn't have a lot of false color and distortion. That's why they're so expensive. On his web site, Ed Ting relates that Al Nagler once showed him that by removing the Barlow lens built into the Tele Vue Radian eyepiece, you could get an apparent FOV around 100o. But the distortion was a killer!
While Meade and Tele Vue are responsible for the designs, neither makes the eyepieces in their own facilities; production is subcontracted. The advantage of Tele Vue eyepieces in general is that they are made by just a couple of small manufacturers in Japan and Taiwan. Another thing that makes Tele Vue so expensive is each eyepiece is hand inspected, and they do reject a lot of them. However, Meade subcontracts wherever they get the current best price. One retailer reported that upon checking, he found that some of the Meade 4000 series Plossls he had in stock were made in Japan, some in China, and some in Taiwan. This may explain why certain people are happy with their Meade eyepieces, while others regard the same eyepieces less kindly.
Other "American" brands also subcontract the actual production. Eyepieces with the consistently highest quality tend to be of Japanese manufacture, with three firms accounting for the bulk of the subcontract work. Vixen is one of those firms, and any eyepiece made by them will be denoted somewhere with a letter V inside a circle. The Celestron Ultima and Orion Lanthanum are Vixen products. Another major Japanese manufacturer (Tanny) denotes its product with a letter T within a circle; they make the Orthoscopics for University Optics and Pocono Mountain Optics, among others. Kasai supplies eyepieces, denoted with a "circle K" logo, to a variety of resellers. Pentax and Takahashi are two Japanese manufacturers renowned for high quality optics; some are of their own manufacture, while others are subcontracted to their specs. In particular, the Takahashi LE series is highly prized...and highly expensive.
There have also been good reports about eyepieces made in Russia, primarily from the Intes company. Eyepieces made in China and Taiwan are sometimes very good, but often suffer from inconsistent quality. Much depends on the quality orientation of the supplier who actually puts their brand name on the eyepiece you buy.
Orion's Optilux wide field oculars illustrate how things can get complicated due to subcontracting. If you compare them with the 32mm and 40mm 2-inch format Koenig eyepieces from University Optics, they appear to be identical. In fact, they are the same eyepieces. Orion contracts their Optilux production to the firm in Japan where University gets their Koenigs, except that Orion is not allowed to use the "Koenig" designation. Another tipoff: the prices are almost identical.
The Lanthanums touted by Orion are good eyepieces that many observers describe as "comfortable to use". Their claim to fame is having at least one of the lenses made of the rare earth element lanthanum to provide freedom from aberration. But lanthanum is not so "rare"; it's the same element found in ED (enhanced dispersion) lenses used in many eyepieces by other firms such as Tele Vue and Pentax.
Another high-end product you've probably seen advertised is Brandon eyepieces, sold exclusively by the VERNONscope company. They are premium quality Plossls that for many years were regarded as the epitome of eyepieces. They also happen to be quite expensive. There is one annoyance: the filter threads do not match standard filters, so you either have to get an adapter or purchase only Brandon filters. The consensus of users is that they are still very good eyepieces; however, newer designs from other suppliers offer wider fields, equal contrast, and longer eye relief at comparable or lower prices (plus standard filter threads). It seems this is a product that enjoys a mystique out of proportion to its true merit.
The best source of info is your own set of eyes with your own telescope. That's because, to some extent, the performance of eyepieces is dependent on the telescope's design and focal ratio. At an observing session you might be able to borrow someone else's eyepiece and try it on your scope. Switch between several eyepieces if you can; differences will become more obvious. The so-called premium eyepieces generally fare very well in this type of comparison. That said, when it comes to the investment in a good eyepiece, "good" doesn't necessarily have to equate to "expensive".
Why a 2-inch Eyepiece?
Finally, this is probably a good place to bring up the subject of eyepiece barrel size. A long focal length eyepiece (around 32mm and up) will give you a very wide actual field of view, but to gain the most value from such a long focal length, the eyepiece should be in the 2-inch format, rather than 11/4-inch. If not, the barrel of the eyepiece itself will cut off some of the field that you'd otherwise be able to see. We're referring here to the true field, not just the apparent FOV that is always advertised. Of course, you'd need a 2-inch focuser, but the potential increase in the angular field of view is roughly 2" + 11/4" = 1.6, or a 60% increase.Published in the July 2001 issue of the NightTimes