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Tele Vue Nagler T5 31mm 82° Eyepiece - 2"
The Type 5 31mm Nagler delivers the maximum possible true field of view in a 2-inch format while maintaining an expansive 82° apparent field. Known affectionately as "The Terminator," this six-element powerhouse is designed to provide a spacewalk perspective that remains sharp across the entire focal plane. It serves as the definitive low-power tool for large-aperture Dobsonians and fast refractors where framing massive celestial structures is the priority.
True Field and Edge Performance
By utilizing a 42mm field stop, the 31mm Nagler pushes the physical limits of the 2-inch barrel to maximize the amount of sky visible at moderate magnifications. This allows for high-contrast views of expansive targets like the Orion nebula or the Pleiades without sacrificing the magnification needed to resolve fine structural details.
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Nagler Contrast: Full multi-coatings and blackened lens edges eliminate internal reflections, ensuring a dark background sky even near bright lunar or planetary targets.
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Field Correction: The Nagler design effectively minimizes astigmatism and lateral color, keeping star points tight and undistorted from the center to the field stop.
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Eyeglass Compatibility: 19mm of eye relief ensures that most observers can take in the full 82° field without removing their glasses.
Handling and Mechanical Considerations
Due to its significant 2.2 lb mass, the 31mm Nagler requires intentional management of telescope balance and focuser tension. The rubberized grip ring ensures secure handling in cold environments or when wearing gloves, providing confidence during eyepiece swaps.
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Focuser Load: The weight of this eyepiece can cause slip in friction-based focusers; ensure your drawtube tension is adjusted to prevent focal shift.
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Storage: Given its physical volume, this eyepiece requires a dedicated large-format foam cutout in your accessory case to prevent movement during transport.
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Safety Taper: The 2" barrel is machined with a safety undercut to prevent the eyepiece from falling out of the diagonal or focuser should the set screw loosen.
Operational Comparison
Flagship eyepieces are defined by the trade-off between apparent field, exit pupil, and physical portability.
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vs. Tele Vue 41mm Panoptic: The 41mm Panoptic offers a slightly larger 46mm field stop, but the 31mm Nagler provides higher magnification and a much more immersive 82° apparent field.
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vs. Tele Vue 31mm Nagler (Type 4): While the Type 5 is the modern standard, the previous Type 4 designs focused on even longer eye relief at the cost of a slightly larger physical footprint.
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Will the 31mm Nagler work well with an f/4.5 telescope?
Yes, but it produces a 6.9mm exit pupil; if your eye's pupil cannot dilate this wide, you will lose light and may see the secondary mirror shadow in reflectors.
Is a Paracorr necessary for this eyepiece?
In fast Newtonian systems (f/5 or faster), the wide field will make mirror coma very obvious at the edges, so a Tele Vue Paracorr is highly recommended to maintain sharpness.
Can I use the 31mm Nagler on a 1.25" focuser?
No, this is a dedicated 2" eyepiece; the 42mm field stop is physically too large to be supported by the 1.25" format.
How do I prevent the eyepiece from fogging?
Due to the large mass of glass, it takes longer to reach ambient temperature; using dew heater strips or keeping the eyepiece in a pocket when not in use is recommended.
Does it include Dioptrx compatibility?
Yes, the top of the eyepiece is designed to accept Tele Vue Dioptrx astigmatism correctors, allowing for glasses-free observing.
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| Model # |
EN5-31.0 |
| Focal Length |
31 mm |
| Barrel Size |
2" |
| Apparent Field of View |
82° |
| Eye Relief |
19 mm |
| Field Stop Diameter |
42 mm |
| Weight |
2.2 lbs (1000 g) |
| Elements/Groups |
6 / 4 |
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Tele Vue 5-Year Limited Warranty
