Sixteen millimeters is the all-rounder focal length in a 1.25" barrel. In a 10-inch f/5 Dob, it gives you 78x — high enough to darken the sky background and pull detail out of nebulae, low enough to hold a full degree of true field for open clusters and galaxy groups. In a 4-inch f/7 refractor, it delivers 45x with a 1.8° field: the deep-sky workhorse. At 6 ounces, it barely changes the balance of any scope, and at 7 elements it holds contrast and sharpness across an 82° field that makes standard eyepieces feel cramped. This is the eyepiece owners describe as the one they reach for first.
The Optics
Seven elements, fully multi-coated. The 82° design strikes a practical balance — wide enough to be immersive, simple enough to keep contrast high and weight low. The image is sharp across the center and middle zones with well-controlled astigmatism. One owner uses it on a 10-inch Dob and a 6-inch Meade ACF; another pairs it with a 4-inch refractor. Cloudy Nights members note that edge correction at f/5 is not quite as tight as the shorter focal length UWAs in the line — the 13mm, 10mm, and 7mm are sharper to the edge at fast ratios. In slower scopes (f/6 and above), the difference narrows and most observers report excellent performance across the field. A detailed CN comparison with the 16mm Nagler Type 5 found the Nagler has better edge correction, but the AT 16mm UWA has noticeably more eye relief and costs significantly less. Both delivered sharp center-field images.
1.25" Barrel
This eyepiece fits any 1.25" focuser, diagonal, or Barlow — universal compatibility. A safety groove is machined into the barrel to engage your focuser's thumbscrew. At 6 ounces, it's lighter than most kit eyepieces, and it won't tip the balance on even the lightest refractor or tabletop Dob.
Waterproof
O-ring sealed and waterproof. The practical benefits: no internal fogging at cold temperatures, no dust intrusion, and the internal coatings stay protected from humidity and fungus for the life of the eyepiece.
What's Included
- Astro-Tech 16mm 82° UWA 1.25" eyepiece
- Lens caps (top and bottom)
Features
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82° apparent field of view — Nearly three times the sky area of a 50° Plossl. Wide enough to show deep-sky objects in context with their surrounding star fields.
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7-element fully multi-coated optics — High contrast and edge sharpness. Fewer elements than 100° designs means less scattered light.
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16mm focal length — The versatile mid-power focal length. 78x in a 1250mm Dob, 45x in a 714mm refractor, 127x in a 2032mm SCT. Useful on everything from nebulae to planets.
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12mm eye relief — Comfortable without glasses. Tight for eyeglass wearers.
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Waterproof, O-ring sealed — Cold-weather performance, dust resistance, coating protection.
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1.25" barrel with safety groove — Fits any 1.25" focuser, diagonal, or Barlow. Thumbscrew retention.
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6 ounces — Light enough for any scope. No balance issues.
Under the Night Sky
In a 10-inch f/5 Dob at 78x, the 16mm UWA sits in the sweet spot between wide field and useful magnification. M42 shows the wings of nebulosity extending out from the Trapezium with the sky background dark enough to bring out faint structure. M13 begins to resolve individual stars across its face, not just at the edges. M27, the Dumbbell, shows its apple-core shape clearly against a dark field.
In a 4-inch refractor at 45x, you get a 1.8° true field — the Double Cluster fits comfortably with surrounding star field. The Pleiades show all the bright members. M35 and its companion NGC 2158 share the field, the main cluster resolved into bright chains and the companion a soft glow behind it.
On planets, 78x in a 10-inch is a useful starting magnification. Jupiter shows both equatorial belts and the Galilean moons as distinct points. Saturn's rings are clearly separated from the globe. The wide 82° field gives you generous drift time on an untracked Dob.
Community Says
The 16mm is the most discussed focal length in the UWA line on Cloudy Nights. A detailed side-by-side comparison with the 16mm Nagler Type 5 found the Nagler has better edge correction, but the AT 16mm UWA has noticeably more eye relief and costs significantly less.
— Cloudy Nights 16mm Nagler T5 vs AT 16mm UWA comparison. This owner tested both in a TV-76 refractor and measured the eye relief, parfocality, and edge correction differences in daylight and at night.
In fast scopes at f/5, CN members note the 16mm shows more edge softening than the shorter focal length UWAs — the 13mm, 10mm, and 7mm are sharper to the edge at fast ratios. In slower scopes (f/6 and above), the difference narrows and most observers report excellent performance across the field.
— Cloudy Nights UWA Eyepieces discussion. This owner, an experienced reviewer, contextualized the 16mm's edge performance against the full UWA line and emphasized that scope focal ratio matters more than the eyepiece itself.
Observing Tip
The 16mm UWA makes an excellent first upgrade from a kit Plossl. It delivers more field, better contrast, and sharper edges than most 25mm Plossls while providing more magnification. If you're building your first serious eyepiece set, start here — the 16mm covers the most ground across the widest range of objects and telescopes. Add the 7mm UWA for high power and the 10mm for a step between them, and you have a three-eyepiece set that handles everything from rich-field scanning to planetary detail.
FAQ
Is this parfocal with the other UWAs in the line?
Yes — confirmed by Cloudy Nights members. One owner tested all five 1.25" UWAs (4mm through 16mm) and confirmed they are parfocal with each other. Another measured the 16mm UWA and 4mm UWA at about 1.3mm apart in focus position — close enough that a small touch of the focuser is all that's needed. The UWAs are not parfocal with TeleVue Group B eyepieces, so if you're mixing brands, expect a larger focus adjustment.
How does this compare to a 15mm Plossl?
The 82° UWA shows nearly three times more sky than a 50° Plossl at the same focal length, with better edge correction and higher contrast. The Plossl wins on simplicity (fewer elements), eye relief (Plossls at this focal length typically have longer eye relief), and price. But the viewing experience is in a different category.
Can I use this with a 2" diagonal?
Yes, with a 1.25" adapter in your 2" diagonal. Most 2" diagonals come with a 1.25" adapter. The eyepiece will also work directly in any 1.25" diagonal.
Is this good for astrophotography?
Eyepieces are designed for visual use, not imaging. For astrophotography through a telescope, you'll want a camera adapter that connects directly to the focuser or a dedicated camera eyepiece projection system. This eyepiece is optimized for the eye, not a camera sensor.
Final Thoughts
The 16mm UWA is the workhorse of the 82° line — the eyepiece that handles more targets on more telescopes than any other focal length in the set. It's the mid-power choice that works on nebulae, clusters, galaxies, and planets without being specialized for any one of them. At 6 ounces and 1.25", it fits every scope and changes the balance of none. Eight five-star reviews from owners using everything from 4-inch refractors to 10-inch Dobs say the same thing: this is the eyepiece you put in first and take out last. If you're buying one UWA to start with, this is a strong choice.
