Pentax 5mm XW extra wide angle eyepiece


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This short focal length Pentax eyepiece has a very wide 70° field of view and very long 20mm eye relief, a uniquely useful combination not matched by other eyepieces . . .
Our Product #: PXW05
Pentax Product #: 70512
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Product Description

This short focal length Pentax eyepiece has a very wide 70° field of view and very long 20mm eye relief, a uniquely useful combination not matched by other eyepieces. It uses eight lenses in five groups to provide outstanding medium to medium high magnification astronomical observing with short focal length refractors and fast focal ratio/short focal length Dobsonian reflectors. Its long eye relief is particularly helpful if you must wear eyeglasses while observing, although all observers will benefit from its wide field and sharp images. It provides about the maximum usable magnification with a typical 8" or 10" f/10 Schmidt-Cassegrain telescope. It has good contrast for seeing subtle lunar and planetary details, and for seeking out small planetary nebulas.

It will generally be useful with long focal length refractors, reflectors, or catadioptric scopes only under very good or better seeing conditions. Average seeing will limit its usefulness. Using it with a 2000mm 8" f/10 Schmidt-Cassegrain, for example, will result in 400x (50x per inch of aperture) and a 0.5mm exit pupil (about 1/50th of an inch across). Both of these are very close to the generally-accepted maximum values of magnification per inch of aperture and exit pupil size for usable observing under good to very good seeing conditions for a reasonably experienced observer.

Tech Details

Barrel Size 1.25"
Eye Relief 20mm
Field of view 70
Focal Length 5mm
Number of optical elements 8
Weight 14 oz
Warranty Limited Lifetime


Review by:
I bought this eyepiece from Astronomics several years ago and it has always been my go-to high power eyepiece. The field is reasonably wide, and sharp to the edge, even at f/5. Colors seem very true. In my opinion, it's as good or better than any other premium eyepiece for its focal length and apparent size of field. The eye relief is great and eye placement is easy, and adjustable, with the helical threaded eyecup. Coatings are very very good also. (Posted on 9/10/2019)
Review by:
Always buy quality. You'll never regret it or question what you spent. That certainly applies to optical gear and Pentax makes some of the best. This XW 5mm is worth the money. Clear undistorted views. I could easily distinguish four or five bands on Jupiter with an inexpensive 4 inch refractor. The eyepiece won't correct the chromatic aberration of a singlet, but it can give you clarity. The eyepiece is usually more than half the glass of your telescope/eyepiece combination so make it as good as you can afford. Telescopes come and go, but a quality eyepiece is forever. (Posted on 9/10/2019)
Review by:
I'm not an off-the-deep-end eyepiece junkie who owns 50+ eyepieces and is constantly searching for that magical eyepiece that will make a backyard scope perform like the HST. That said - I have a lot of EPs. Some cheap, some expensive, some great, some not so much. I have a range of scopes of different designs and apertures. I look at the moon, at the planets, at double stars, and when I can get to dark skies, at PN's and galaxies. SO what's my point? Out of all my EPs, for all my different types of observing, the Pentax XW 5mm one of my top 3 favorites and gets used pretty much every observing session. I have seen equal but not better on moon, Jupiter, Saturn, Mars. Despite its complicated design relative to e.g a Plossl or orthoscopic, it manages to put up a crisp contrasty sharp image, and is easy on the eye to use. And it has nice light transmission and works really on galaxies and PNs. Colors look nice and true on double stars. This EP is expensive but worth the price. (Posted on 11/26/2018)
Review by:
A fantastic eyepiece with a wonderful adjustable eyepiece cup, making this one of the most comfortable eyepieces in this focal length going. The optics and coatings are the very best and the view through this ocular matches many high end Orthoscopics. It is a tall and somewhat heavy eyepiece that may prove unwieldy on small refractors?? (Posted on 11/5/2018)
Review by:
I find the XW series of Pentax eyepieces to be very comfortable with ample eye relief for both glasses wearers and non glasses wearers. There is a nice adjustable guide that helps you get your eye placed in the perfect spot to use. The view is spectacular in my refractors and reflectors (although the magnification is a bit high in my reflector). (Posted on 10/6/2018)
Review by:
I want to love this as much as I love my 20 XW. But I don't. And I think it might be due to the skies in my area and perhaps the scope. The views are not as sharp the 20. If I get a different opinion I will update this, but for now, it's just ok. The quality of the EP is great and the eye relief is nice too. If you have super clean skies, I wouldn't hesitate to try it. (Posted on 8/4/2017)
Review by:
The XW series of Pentax eyepieces are my go-to tools for most every observing session. I observe with a f/7 3.5" undriven refractor. The magnification of the 5mm XW is hitting about as high as I like to go in the city. The eye relief is generous (I observe with glasses) and the clarity/quality of the image surpassed anything else I've tried in the same FL. You may upgrade your scope, but this eyepiece will stay with you. (Posted on 8/4/2017)
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