7mm XW extra wide angle eyepiece

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This wide field Pentax eyepiece is designed for high power observing of objects on the ground by day and in the skies at night.

Terrestrially, it is the most powerful eyepiece usable for nature studies with the 80mm and 100mm Pentax spotting scopes under brightly lit observing conditions.

Astronomically, it’s an excellent choice for high power lunar and planetary observing with long focal length refractors, reflectors, or catadioptric scopes under good to somewhat better than average seeing conditions. It is also exceptional for medium power viewing with short focal length refractors and fast focal ratio Dobsonian reflectors. It has eight lenses in a six group optical design. This gives a sharpness across its very wide 70° field that makes smaller globular clusters vivid and nearly three-dimensional. It is also more or less regularly useful for astronomical observing with long focal length telescopes, but below average seeing conditions will limit its performance. If so-so seeing is the norm where you observe, its 7mm focal length may 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 71x magnification and a 52’ 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 74x magnification and a 50’ field of view at 1000 yards.
With the 100mm aperture Pentax spotting scope this eyepiece provides 90x magnification and a 41’ field of view.
In all cases the spotting scope exit pupil will be in the neighborhood of 1mm, providing somewhat dim images if the scene being observed is not brightly lit.

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:
52x terrestrially
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.

7mm
Number of optical elements:
8
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.
14.3 oz
Warranty:
Limited Lifetime
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Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(5.00)   # of Ratings: 4   (Only registered customers can rate)

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1. Chris on 4/2/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Pentax XW 7mm is my main workhorse. I use a f/7 3.5" refractor. This eyepiece hits the sweet spot for me - the contrast is excellent, and edge to edge it provides better sharpness than any other I've used. If I were limited to only 2 eyepieces, this would be one (the other would be 13mm Ethos). Pentax did a quality job on every aspect of this eyepiece, and you won't be disappointed should you choose to invest in it.
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2. Robert on 3/15/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Perfectly free of astigmatism or field curvature right to the field stop. Great contrast and easy viewing with eyeglasses. The FOV is very immersive and hard to distinguish from that of a Televue Delos which is supposed to be 2 degrees wider. This eyepiece definitely feels wider than a 68 degree Panoptic. That could be due to the generous eye relief. Highly recommended for a nice step up in power from a 10mm XW or Delos.
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3. Al on 3/11/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
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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4. Mike on 9/15/2012, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
This is just an impeccable higher power eyepiece, flat to the edges, crystal clear, works expecially well in refractors. I would never trade or sell this one.
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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 - 7mm XW extra wide angle eyepiece

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Pentax - 7mm XW extra wide angle eyepiece
 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 5.00 | Users: 4)  Only registered users can submit ratings - Register Here
Our Product #: PXW07
Manufacturer Product #: 70513
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This wide field Pentax eyepiece is designed for high power observing of objects on the ground by day and in the skies at night . . .





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