Astro-Tech 13mm 100° field waterproof 1.25"/2" eyepiece


Availability: In stock

The Astro-Tech 13mm o-ring sealed 1.25"/2" eyepiece combines a high power capability with a 100° apparent field to provide a jaw-dropping observing experience in your telescope at a price that is unreal.

Our Product #: ATXWA13
Astro-Tech Product #: ATXWA13
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Product Description

The 13mm 100° field o-ring sealed Astro-Tech eyepiece is designed for maximum field/medium power deep space use with telescopes having focal ratios down to f/4. It is exceptionally effective on nebulas with fast f/ratio reflectors, such as Dobsonians, giving both an immense field and a bright exit pupil (over 3mm with the typical f/4.5 Dob). Its very wide field also makes it convenient for moderate power lunar and planetary observing with Dobsonians, as you have much longer to observe before the planet drifts out of the field and the scope has to be repositioned. That said, it is worth noting that the 13mm Astro-Tech is marvelous for open clusters, nebulas, galaxy clusters, and globular clusters with any telescope.

The 100° apparent field of this 13mm Astro-Tech eyepiece is nearly 50% larger in area than an 82° field eyepiece. You could get a similar true field with a longer focal length (but narrower apparent field) conventional eyepiece, but the 13mm Astro-Tech has the benefits of the higher power and darker sky backgrounds that are inherent in its shorter focal length.  The eyepiece consists of nine elements in six groups.  The lens elements are fully multi-coated and have blackened lens edges to improve contrast and eliminate light scatter.

The 13mm Astro-Tech 100° field eyepiece is O-ring sealed against water. While waterproofing might seem important only for observing underwater, waterproofing serves five useful purposes for the astronomical observer as well.

One, internally sealing the eyepiece helps prevent internal fogging in the eyepiece when observing at very low temperatures. Two, for observers in dusty climates, it halts the intrusion of wind-blown dust and fine particulates into the eyepiece body. Three, for observers in very humid climates, it prevents the growth of fungus on the internal lens elements. Four, for all observers, it maximizes the life of the internal optical coatings. And finally, five, the waterproof 13mm Astro-Tech eyepiece is easier to clean, as there is no risk of cleaning solution migrating from the top of the lens and seeping around edges to be trapped in between elements. 

There is a soft rolldown eyecup to shield the eye from ambient light (from a neighbor’s security light, for example) and improve the image contrast. At an eye relief of 15mm, the 13mm Astro-Tech might vignette some eyeglass wearers. However, since the 100° field is so wide that you can't see the full field without having to move your head from side to side to take it all in anyway, vignetting in the conventional sense is not a problem.

The 13mm Astro-Tech has high contrast, comfortable eye relief, and full field sharpness – with well-controlled astigmatism, field curvature, and lateral color. The 9mm Astro-Tech fits 1.25" or 2" focusers or diagonals.  A safety groove is machined into the barrels to engage your focuser thumbscrew. This helps prevent the eyepiece from falling should the thumbscrew accidentally loosen while observing.  The eyepiece comes with a 2" collar that is removable exposing a 1.25" barrel.

Tech Details

Barrel Size 1.25" and 2"
Eye Relief 15mm
Field of view 100°
Focal Length 13mm
Number of optical elements 9
Weight 19 oz.
Warranty 1 year


Review by:
Great pinpoint images, M-27 looked awesome through it as did everything else we looked at through this huge eye piece. Jupiter really needed a N.D. filter for best views as it is so bright through this ocular. To really enjoy this at its best your going to need an assortment of 2" filters. This is a very good buy for a ocular of this type and quality and I plan on getting a couple more. (Posted on 10/23/2022)
Review by:
I was a bit skeptical on the purchase of this eyepiece, but my first night out and wow! I have had an ES 14mm 100 degree in the past which also blew me away, and this is identical in terms of image quality and also affords the ability to use as a 1.25 inch eyepiece to use with a good barlow. I have used it with a GSO apochramatic 2.5x barlow (actually 2.15x is what others are telling me) with excellent results. Eye relief is good, and you will need to remove your eyeglasses to get the full immersive effect, but well worth it. You can still view much of the FOV with glasses on. I use this in a 14 inch f/4.64 dobsonian with no Paracorr, and only see coma on the outer 10+/- percent of the FOV, but I need that additional FOV to help me navigate my manual dobsonian. Build quality is very good, maybe not on par with the Ethos, but the image quality is just about on par with the Ethos. Highly recommend this eyepiece for any telescope. (Posted on 8/28/2022)
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