18mm 82° field waterproof 2" eyepiece

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This 2” 18mm Explore Scientific is an exceptional medium focal length eyepiece with a wide, wide 82° field. It makes observing feel like you’re floating above the Earth, taking a space walk, rather than looking through a telescope eyepiece, particularly with short focal length scopes such as fast focal ratio apo refractors or Dobsonian reflectors.

In addition to its wide field, the 18mm Explore Scientific has an extra benefit for you. It is O-ring sealed and nitrogen-purged to be 100% waterproof. This prevents internal fogging in the eyepiece; keeps the interior dust-and fungus-free; and makes it easier to clean, as there is no risk of excess cleaning solution getting trapped between the lenses.

The latest computer design programs have been used to optimize its performance. Its six element/four group design uses low dispersion and high refractive index lenses and full multicoatings for high contrast, high resolution, and flat field images across its very wide 82° field of view. The lens edges have been blackened to improve contrast.

A 10" f/4.5 Dobsonian reflector will have a full 1.29° field at 63.5x with this eyepiece, able to encompass all of the Pleiades in one field. Even an 8” f/10 catadioptric will have a field almost one and a half lunar diameters across, able to encompass the full Moon with room to spare, the Orion Nebula, and many globular clusters, as well. You can use the calculator in the "formula" tab above to see just how wide the field will be with your particular telescope.

At 13mm, the eye relief will somewhat vignette the field of view for eyeglass wearers. This isn’t as much a problem as you might think, as the 82° field of view is so wide that even non-eyeglass wearers have trouble seeing the whole field at once. All observers have to move their eye from side to side to take in the immense view, so vignetting in the conventional sense is not a problem. This is one of those eyepieces that can truly be described as showing you a “picture window view” of space. The visual effect of its long eye-relief and 82° apparent field is truly a full-immersion experience. Your eye is relaxed, allowing you to easily use the “averted vision” technique to study faint details across its huge field of view.

The eyepiece has a soft fold-down rubber eyecup and comes with dust covers for both ends of the eyepiece.

This individually serial numbered Explore Scientific eyepiece is backedby a limited one year warranty, which will be extended to an ExploreScientific transferable product lifetime limited warranty when its warranty card is registered with Explore Scientific within 60 days of purchase.With the extended product lifetime warranty, this Explore Scientificeyepiece will be protected for as long as it continues to bemanufactured, plus an additional five years. Full details on this unique transferable lifetime warranty.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
82°
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

13mm
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

18mm
Number of optical elements:
6
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
2"
Weight:
The weight of this product.
14 oz.
Warranty:
1 year, extendable to lifetime
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1. christian on 5/25/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
For dsos this eyepiece excels. Combined with a paracorr type 1 M35 looked incredible with pinpoint stars to the edge and awesome contrast. Would have been five stars if not for the yellow ring around the field stop when observing the moon. Good eyepiece.
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2. Neil on 5/15/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I bought this to make it the high end of magnification in the 2" Ep's I have and although I found it had great sharpness when using it on the Moon, it had a wide chromatic aberration on the edges, orange/red ring.
Regular star field use I have found no problem or cant tell if any aberrations on the edges, I have not used it enough for anything to appear to be a problem since Im looking in the center most of the time.
It defiantly has great sharpness and brightness.
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65mm x 80mm eyepiece container
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Helpful Formulas
Telescope Eyepiece Formula
To calculate the magnification and approximate actual field of view of this eyepiece on your telescope, enter the focal length of your telescope below and press the "Calculate" button.

Enter your telescope's focal length: mm   



Explore Scientific - 18mm 82° field waterproof 2" eyepiece

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Explore Scientific - 18mm 82° field waterproof 2" eyepiece
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Our Product #: ES8218W
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This 82° field Explore Scientific 18mm 2” waterproof eyepiece makes observing with many telescopes feel like you’re taking a stroll through the cosmos rather than looking through an eyepiece . . .





. . . our 34th year