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Explore Scientific's 14mm 100[degrees] eyepiece.

US price: $499 ($399 introductory price still in effect at press time)

Explore Scientific

7401 Katelyn Ct., Suite A, San Diego, CA 92120


No product in recent memory has received more universal acclaim from the observing community than Tele Vue's 13-mm Ethos eyepiece introduced in mid-2007--the first astronomical eyepiece offering a 100[degrees] apparent field of view. With such rave reviews, it's not surprising that a year and a half later there are more than a dozen 100[degrees] eyepieces on the market. What is surprising, however, is that there are now four companies offering them. Newcomer Explore Scientific was the next company to jump on the 100[degrees] bandwagon, announcing 14-, 9-, and 20-mm eyepieces in quick succession. And recently TMB Optical and Zhumell have each announced 16- and 9-mm models.

Last fall and winter I tested the Explore Scientific 14mm 100[degrees] Series Nitrogen-Purged Waterproof Eyepiece. While the name is a bit of a mouthful, it accurately describes two features that set the ocular apart from all other astronomical eyepieces, not just 100[degrees] models--its waterproof design and nitrogen-filled body, which are said to eliminate internal fogging of the lenses. Except for a youthful acquaintance of mine who tried to clean a set of eyepieces by running them through a dishwasher (true story!), I've never heard of water damage to the inside of an eyepiece. Nevertheless, both features are good things, especially for those of us who observe in dewy conditions and/or use liquid lens cleaners.

As with the other 100[degrees] eyepieces announced by Explore Scientific, the 14-mm model fits only 2-inch focusers, which are pretty much standard fare on today's telescopes. The barrel is threaded for standard 2-inch filters, and it has a large, tapered "safety" groove, which allows it to be securely gripped in any holder that has thumb-screw locks or a compression-ring clamp. Furthermore, the tapered design prevents the groove from snagging a compression ring and being difficult to remove from a holder, as sometimes happens with eyepieces having sharp-edged safety grooves.

The only noteworthy mechanical aspect of the Explore Scientific 14-mm eyepiece that might be considered a downside is its weight. At 31 ounces (0.88 kg), the eyepiece is heavy, and it's 11 ounces (55%) heavier than Tele Vue's 13-mm Ethos. This was enough to upset the balance of my 12-inch Dobsonian, forcing me to tighten the friction clamp on the altitude axis more than I like for optimal "feel." The solution, of course, would be to have an adjustable counterweight on the scope, and I would certainly consider adding one if I owned the eyepiece.

This minor issue, however, was quickly forgotten the moment I looked through the eyepiece. The view was everything one would expect from a premium eyepiece--crisp, contrasty views with round, pinpoint stars across a field so big that I had to roll my eye around to see it all. There is a very slight pincushion distortion at the edge of the field, which I only noticed when I was sweeping large, "solid" objects such as the Moon in and out of the field. As long as I kept my eye centered in the eyepiece's exit pupil, there were no visible color fringes even on the Moon's brilliant, high-contrast limb. The times when I did note a thread of green along the limb served as a reminder that my eye wasn't centered properly.

I tried the eyepiece on a variety of telescopes, ranging from the 12-inch Dob down to a 92-mm apo refractor, all with excellent results. Perhaps the most demanding test came with the eyepiece fitted to a 4-inch, flat-field apo. Under critical examination I could detect a slightly different focus position for stars at the center and edge of the field, indicating the eyepiece has a very mildly curved focal surface. This focus shift was tiny, however, and I suspect much of the reason I could see it at all is because my eyes have lost virtually all of their focus accommodation as I've grown older. Observers with accommodating eyes will likely see perfectly sharp stars when they concentrate on the center and edge of the field without adjusting the focus.

Just about any way you look at and through it, the Explore Scientific 14mm 100[degrees] eyepiece is a winner.



Excellent image quality Top-notch construction


Significantly heavier than competing eyepieces
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Title Annotation:Quick Look
Author:di Cicco, Dennis
Publication:Sky & Telescope
Article Type:Product/service evaluation
Date:Apr 1, 2010
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