4.7mm 82° field argon-purged waterproof 1.25" eyepiece

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This 82° 4.7mm Explore Scientific is an excellent short focal length/ultra wide field eyepiece with an unusual benefit. It is O-ring sealed and argon-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 seven 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 a very wide 82° field of view. The lens edges have been blackened to improve contrast.

The 4.7mm 82° Explore Scientific works with any telescope from a fast focal ratio reflector to a long focal length refractor or Maksutov. It’s particularly good with Dobsonians and fast focal ratio refractors, providing high magnification with a very wide field of view for observing smaller globular clusters and compact nebulas.

At 14mm, the eye relief is surprisingly good for such a short focal length eyepiece, although eyeglass wearers will still see a somewhat vignetted image. This is not 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. This is an eyepiece that shows you a “picture window view” of space for a true full-immersion observing experience. With its unconstricted view, your eye relaxes, allowing you to easily use the “averted vision” technique to study faint details across a huge field of view.

You can use the calculator in the "formula" tab above to see just how wide the field will be with your particular telescope. For example, it will give you a 0.54° field (slightly wider than the full Moon) at 152x with a 4" f/7 refractor like the Explore Scientific 102mm triplet apo refractor.

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 backed by a limited one year warranty, which will be extended to an Explore Scientific transferable lifetime limited warranty when its warranty card is registered with Explore Scientific within 60 days of purchase.  Here's a link to the 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.

14mm
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.

4.7mm
Number of optical elements:
7
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
1.25"
Weight:
The weight of this product.
7.5 oz.
Warranty:
1 year, extendable to lifetime
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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   



4.7mm 82° field argon-purged waterproof 1.25" eyepiece

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4.7mm 82° field argon-purged waterproof 1.25" eyepiece
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Our Product #: ES8204A
Manufacturer Product #: EPWP8247-01
Price: $139.99  FREE ground shipping - Click for more info
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MSRP: $311.99
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This 4.7mm Explore Scientific 82° field argon-purged waterproof eyepiece is an excellent very high power, very wide field waterproof eyepiece for resolving globular clusters and closely-spaced binary stars.





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