Explore Scientific 68° Argon-Purged 40mm Waterproof Eyepiece - 2" Barrel Size
Longer Eye Relief with a Pleasing Field of View
There are several things to consider when contemplating the purchase of a new Explore Scientific eyepiece, and customers often ask for our help when they are pondering choices in focal length, field of view, and eye relief. We can certainly help narrow the field, so to speak, by asking some targeted questions, but when it comes right down to it, choosing the "perfect" eyepiece from that point on is all about personal preference.
To some, the most important feature of an eyepiece (besides a sharp, clear image!) is a wide field of view, while to others, long eye relief is #1 on their "must have" list. And to make things even more complicated, prerequisites for an eyepiece used mainly for lunar and planetary viewing are usually different than those required for huge objects like galaxies and nebulae. That is why Explore Scientific offers a wide variety of eyepiece designs; so that you can pick the features you require and desire, whether you are investigating the deepest reaches of space, the Great Red Spot on Jupiter, or migrating whales just off the coast of California.
The Explore Scientific 68° Series Eyepieces were designed for those who prefer longer eye relief but still want to enjoy a field of view that is wider than a classic Plossl or Orthoscopic style eyepiece. If you wear eyeglasses and either want or need to keep them on while observing, the extra long eye relief built into the 68° models will allow you to do that and still observe comfortably. As you can see from the chart shown above, the eye relief in this series starts at almost 12mm on the 16mm model and increases quickly until it reaches a maximum of 31mm on the 40mm model. There are four Explore Scientific 68° eyepieces…the 24mm, 28mm, 34mm, and 40mm…that sport an eye relief of over 18mm, which is perfect for eyeglass wearers. If you wish to increase the magnification of these eyepieces while still maintaining their superb eye relief, use them with the appropriate Explore Scientific Focal Extender, which comes in both 1.25" and 2" barrel sizes.
Of course, you do not have to wear eyeglasses to appreciate comfortable eye relief, or the quality that lives in each Explore Scientific 68° eyepiece. From the rubber grip and folding eyecup to the enhanced EMD coatings for superb contrast, we think you'll agree that these eyepieces are a perfect solution for dropping the power down on your telescope, which will increase the exit pupil size and allow you to see the faintest objects that your telescope is capable of.
Explore Scientific 68° Eyepiece Highlights
Optimized Optical Design - Explore 68° Series Eyepieces are optimized through each design, fabrication, and testing process to produce high contrast, high resolution images.
Durable Coatings & Finishing Touches - Each element in your Explore Scientific 68° eyepiece is fully multi-coated, resulting in bright, sharp images, and every element has blackened edges to reduce internal reflections and increase contrast.
Waterproof, Fog-Proof Housing - The internal optics of all 68° Series eyepieces are housed in a gas-purged, waterproof barrel that keeps them as pristine as the day they were manufactured. Cleaning is much easier, and there is no need to worry about water or fluid becoming trapped in between elements due to rain, spills, heavy dew, or getting over-enthusiastic with lens cleaning fluid.
Tapered Barrel for Extra Security - The insert barrel of each eyepiece is double-tapered to allow smooth insertion to, and removal from, a telescope's eyepiece holder or diagonal, however the wide dimension of the taper helps prevent the eyepiece from falling out of the telescope should the set-screw holding it in place become loose. Barrels are threaded to accept standard screw-on filters.
Optional Focal Extenders for Extra Magnification - Explore Scientific makes a wide variety of eyepiece focal lengths, allowing a change in magnification for just about any observational study you can think of. However, if you would like to get "double duty" out of the eyepieces in your accessory case, while still retaining the eye relief of that eyepiece, use Explore Scientific Focal Extenders.
The Explore Scientific 68° Series Waterproof Eyepiece Using advanced computer design, combinations of low dispersion and high refractive index optical glasses, and durable multilayer deposition coatings, Explore Scientific 68° Series wide field eyepieces are optimized to produce high contrast, high resolution, and superior flat field characteristics.
Each 68° Series Nitrogen-Purged Waterproof eyepiece is internally sealed and purged with inert, dry nitrogen gas to prevent internal fogging, to halt the intrusion of fine particulates and fungus, and to maximize the life of the internal coatings.
The visual effect of these eyepieces with their long eye-relief and their 68° apparent field is a unique experience. Your eye is relaxed, allowing you to easily use the "averted vision" technique to study faint details across a realistic field-of-view. Each eyepiece is meticulously assembled into precision machined metal lens barrels that maintain the perfect alignment of the optical train for years of rugged use in the field.
The 68° Series eyepieces come with a twist-up rubber eye-guard that raise to the desired height for the comfort of the observer, and as experienced astronomers know, eye comfort is critical when trying to observe at the visual limits of the telescope.
To keep internal reflections to a minimum, all internal surfaces of the eyepiece barrel are flat black, as well as the edges of the lenses themselves to minimize the scattering of light within the lenses themselves. In today's modern telescope industry there are many fine companies to choose from manufacturing top quality eyepieces.
Explore Scientific invites direct side-by-side comparison with any other eyepiece of similar design, and they back their eyepieces with an exclusive Five Year Limited Warranty. (Limited Warranty is one year, extended to five years when product is registered within 60 days of purchase.) We think that you will find Explore Scientific eyepieces rank among the finest obtainable and represent an outstanding value.
|Name||Explore Scientific - 40mm 68° Series Argon-Purged Waterproof Eyepiece - 2"|
|Eyepiece Apparent FOV||68|
|Eyepiece Barrel Size||2|
|Eyepiece Eye Relief||31|
|Eyepiece Field Stop||0|
|Eyepiece Focal Length||40|
|Warranty||Explore STAR Transferrable Unlimited Lifetime Product Warranty|