10mm XW extra wide angle eyepiece

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This short focal length Pentax is a high power eyepiece usable for both terrestrial and astronomical observing.

Terrestrially, it is superb for detailed long-distance nature studies with the 80mm and 100mm Pentax spotting scopes under average lighting conditions.

Astronomically, it’s an excellent high power lunar and planetary observing eyepiece with long focal length refractors, reflectors, or catadioptric scopes under average seeing conditions. Its 10mm focal length is an ideal match for an f/10 Schmidt-Cassegrain, providing 200x and a 1mm exit pupil that closely matches the resolution of the scope to that of your eye. Some of the larger globular clusters, such as M13, will fill its 0.35-degree field with such a scope. It is also exceptional for medium power viewing with short focal length refractors and fast focal ratio Dobsonian reflectors. It has seven lenses in a six group optical design for a very wide 70° field. It is regularly useful for astronomical observing with long focal length scopes, but below average seeing conditions may limit its performance somewhat. If so-so seeing is the norm where you observe, its 10mm focal length will often represent the maximum practical with a long focal length scope.

The long 20mm eye relief is ideal for those who must wear eyeglasses while observing due to astigmatism. Even those who do not wear glasses will find the long eye relief a comfortable change from the cramped eye relief that is typical of the usual short focal length eyepiece.

For terrestrial observing . . .
With an 80mm straight-through Pentax spotting scope this eyepiece provides 50x magnification and a 74’ field of view at 1000 yards, which are the values given in the specifications to the left.
With the 80mm angled Pentax spotting scope this eyepiece provides 52x magnification and a 71’ field of view at 1000 yards.
With the 100mm aperture Pentax spotting scope this eyepiece provides 63x magnification and a 58’ field of view.

For astronomical observing . . .
The field of view of 70° degrees given in the specifications to the left is the apparent field of view. The actual field of view will be equal to that apparent field divided by the magnification of the eyepiece/telescope combination.

Power:
50x terrestrially
Field of view 1000 yards:
74'
Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
70 °
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.

20mm
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.

10mm
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.
13.8 oz
Warranty:
Limited Lifetime
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1. Al on 3/11/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
This was my first Pentax eyepiece. I bought this after looking through the same EP belonging to a friend. I was not disappointed! Shortly after purchase, I had an opportunity to compare this with an Ethos 10mm in my 18 inch Starmaster telescope. Other than the Ethos having a wider field of view, the two eyepieces gave identical views of a variety of objects. A couple other seasoned astronomers looked at the same objects and agreed with me.

Great eyepiece. I have been working towards the AL Galaxy Clusters Award, and the EP has been a valuable assistant! Great contrast. Stars are pinpoint edge to edge. Well made. I don't wear eyeglasses except for reading, and I was uncomfortable with a "tunnel vision" effect, until I remembered the adjustable eyecup. Adjusting the eyecup made a good eyepiece a GREAT eyepiece. I would replace it with the same one if I ever lost it!
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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.

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Pentax - 10mm XW extra wide angle eyepiece

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Pentax - 10mm XW extra wide angle eyepiece
 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 5.00 | Users: 1)  Only registered users can submit ratings - Register Here
Our Product #: PXW10
Manufacturer Product #: 70514
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This short focal length Pentax is a high power eyepiece usable for both terrestrial and astronomical observing . . .





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