Tele Vue Nagler 31mm Type 5 — image 1
Tele Vue

Tele Vue Nagler 31mm Type 5

The widest, most immersive low-power view a 2-inch focuser can give, the eyepiece observers simply call the “Terminagler.”

95/ 100
Polaris Score
#1 of 9 low-power wide-field eyepieces
See the breakdown ↓
What it's for
Low power · wide fieldHigh power · narrow field

This is a low-power, widest-true-field eyepiece, the one you reach for to find a target, frame a whole nebula, or sweep the Milky Way. It is not, and was never meant to be, a high-magnification planetary eyepiece.

Apparent Field
82°
Barrel Size
2″
Eye Relief
19mm
Field Stop
42.0mm
Focal Length
31mm
Weight
1.0 kg
From$789

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The spacewalk

You don’t look at a field.
You look into the sky.

Every number on the spec sheet matters less than one feeling: how much sky wraps around your eye. This is why observers fall in love with a piece of glass. Widen the apparent field and watch the black edge of the eyepiece slip away.

82° apparent field

The edge slips into your peripheral vision. You stop looking AT a field and start looking INTO the sky.

At 82°, the edge disappears into your peripheral vision. That is the whole reason this eyepiece exists.
Try this eyepiece on your own scope in the Simulator →
01What it's good at

What it's best at — and the trade-offs.

Sweeping the Milky Way, under a dark sky, low power and a huge true field turn the summer star clouds into a slow, drifting river of stars.
Best at
✓Sweeping the Milky Way, under a dark sky, low power and a huge true field turn the summer star clouds into a slow, drifting river of stars.
✓Framing large nebulae whole, the Veil, the North America, the Rosette, targets too big for most eyepieces sit complete in a single view.
✓Pinpoint stars across the field, even in a fast f/5 scope, stars stay tight and neutral almost to the edge, the hard part of a wide field, solved.
Trade-offs
!Not a planetary eyepiece, low power is the point. For Jupiter’s belts or Saturn’s rings you want a short focal length, not this.
!Big exit pupils need dark skies, in a fast scope it throws a 5–6 mm exit pupil, glorious under dark skies, washed out under city light.
!Heavy, and 2-inch only, a full kilogram of glass rebalances the scope and demands a solid 2″ focuser. Small refractors need not apply.
02In your telescope

One eyepiece. A different job in every scope.

15× in a small refractor, 66× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 15× and 5.3° of sky in a little refractor, or 66× and a tight frame in a long SCT. Here’s what it does across common scopes.

Small apo refractor
480 mm · f/5.5
Magnification
15×
True field
5.3°
Exit pupil
5.6 mm
Ultra-wide. Sweep the whole summer Milky Way and frame the entire Veil Nebula in a single view.
8-inch Dobsonian
1200 mm · f/6
Magnification
39×
True field
2.1°
Exit pupil
5.2 mm
Rich-field deep sky, big open clusters and the largest nebulae float in a dark surround.
12-inch Dobsonian
1500 mm · f/5
Magnification
48×
True field
1.7°
Exit pupil
6.2 mm
Your lowest-power, widest true field, the eyepiece you find and frame with before you zoom in.
8-inch SCT
2032 mm · f/10
Magnification
66×
True field
1.2°
Exit pupil
3.1 mm
Tames a long focal length into a genuinely wide field, large nebulae finally fit in one view.
Exit pupil is how wide the beam of light leaving the eyepiece is. Around 5–6 mm is bright and immersive under dark skies; push much past 6 mm and you waste light, and under light pollution a smaller exit pupil shows more contrast.
03In plain English

The numbers, in plain English.

31mm FL · 82° AFOV · 2″
82° apparent fieldIts whole point
Immersive
As wide as apparent fields get before you step up to a rare, far pricier 100° eyepiece.
19 mm eye reliefGlasses-friendly
Relaxed
Keep your glasses on, sit back from the lens, and observe for an hour without a single squint.
42 mm field stopAs wide as 2″ gets
The maximum
This is the widest true field any 2-inch eyepiece can physically show. Nothing frames more sky.
5–6 mm exit pupilA wide, bright beam
Bright, low power
Pours a broad column of light into your eye, the reason big, faint nebulae glow at this focal length.
1.0 kg of glassRebalance the scope
Substantial
You will feel it. Expect to move a counterweight or slide the tube, a fair price for the view.
Find-and-frameThe default view
First one in
Low power finds the target and frames most of it, the eyepiece you reach for before you zoom in.
04What comes alive

The targets this eyepiece was born for.

The Veil Nebula, The Pleiades, North America Nebula, Orion Nebula + Sword, Andromeda…
The Veil NebulaComes alive
The Veil Nebula
A vast supernova remnant that few eyepieces can frame whole. Add an OIII filter and the tendrils leap out.
The PleiadesComes alive
The Pleiades
The whole cluster with room to spare, hundreds of blue stars set in a wide black frame.
North America NebulaComes alive
North America Nebula
Enormous and faint. Only a low-power, wide-field eyepiece shows the whole continent shape at once.
Orion Nebula + SwordExcellent
Orion Nebula + Sword
The full Sword region in one view, M42, M43 and the surrounding star clouds together.
Andromeda GalaxyExcellent
Andromeda Galaxy
Big enough to fill the field, with both companion galaxies riding along in the same frame.
The Double ClusterExcellent
The Double Cluster
Two open clusters side by side, a low-power target that a narrow field simply cannot hold.
05Role in a collection

Where it sits in your eyepiece case.

Where it sits across 3 focal lengths

A good eyepiece collection isn’t a pile of glass — it’s two or three focal lengths that hand off from wide to tight. This is the anchor at the bottom of the ladder: the one you find and frame with. You buy it once, and it stays your low-power eyepiece for life.

31 mmThis one
Low power · wide field
Find, frame and sweep. Your widest true field and the lowest useful magnification. Exit pupil 5–6 mm.
Veil Nebula · Pleiades · Milky Way star clouds
13 mm
Medium power · the workhorse
Where most deep-sky objects look their best, galaxies, globulars and planetary nebulae at a comfortable scale.
M13 · Ring Nebula · most galaxies
7 mm
High power · detail
Planets, the Moon at the terminator, tight double stars and the smallest planetary nebulae. Steady-air nights only.
Jupiter · Saturn · lunar craters
06Build around it

What it pairs with.

The telescope · Correct it · Filter it
The telescope
What it goes into
Fast Dobsonian · f/4–f/6
Its natural home, low power, wide field, dark surround
Rich-field refractor · f/5–f/6
The widest true field of all: whole-nebula, whole-cluster views
8–11″ SCT
Tames a long focal length into a usable low power
Correct it
What sharpens the edge
Tele Vue Paracorr Type-2
At f/5 and faster, tames coma so the wide field stays sharp corner to corner
2″ star diagonal
For refractors and SCTs, put the eyepiece at a comfortable angle
Parfocal with Naglers
Swap within the line and barely touch the focuser
Filter it
What transforms the view
2″ OIII filter
The Veil and other supernova remnants explode into detail
2″ UHC filter
Broad nebula boost that keeps stars natural
2″ filter thread
Threads straight into the barrel, no adapters
The pairing observers dream about

A big fast Dob, a coma corrector, this eyepiece and an OIII filter, the setup that shows you the whole Veil Nebula in one breathtaking view.

Open this rig in the Simulator →
Telescope
12″ f/5 Dob
Corrector
Paracorr Type-2
Eyepiece
Nagler 31 T5
Filter
2″ OIII
07The Polaris Score

How it scores, and why.

95/100 · #1 of 9 low-power wide-field eyepieces
95/ 100
Tele Vue Nagler 31mm Type 5
#1 of 9 low-power wide-field eyepieces

Judged not by its price but by whether it delivers on its purpose, the widest, most immersive true field a 2-inch focuser can produce. On that measure it is close to perfect, which is why it has stayed in production, essentially unchanged, for two decades.

Optical quality
95
Immersion
100
Comfort
90
Value
85

Polaris weighs how well the eyepiece does the job it was designed for — optics, immersion, comfort and value — never list price or brand.

08Who it's for

An honest fit check.

Own a fast Newtonian, Dob or rich-field refractor with a 2″ focuser
Buy it if you
✓Own a fast Newtonian, Dob or rich-field refractor with a 2″ focuser
✓Observe visually under genuinely dark skies
✓Chase big targets, nebulae, star clouds, the Milky Way
✓Wear glasses and want long, relaxed viewing
Look elsewhere if you
!Observe mostly from light-polluted city skies (a big exit pupil washes out)
!Have a small or slow scope, or only a 1.25″ focuser
!Mainly chase planets and the Moon, you want high power, not this
!Are building a first eyepiece kit (start with a 32 mm Plössl)
09The numbers

Full specifications.

25 measured and stated values
Optical
Focal Length31mm
Apparent Field82°
Field Stop42.0mm
Elements6 elements
CoatingsFully multi-coated
Exit Pupilf-ratio dependent
BlackeningEdge-blackened lenses
Comfort & handling
Eye Relief19mm
Eye LensLarge · easy to look into
EyeguardFixed
GlassesFull field with glasses on
ParfocalWith Nagler / Panoptic line
GripRubber safety undercut
Fit & build
Barrel Size2″
Filter Thread2″ (M48)
Weight1.0 kg
Length5.2″
Top Diameter3.1″
BodyAnodized aluminium
Origin & warranty
LineNagler Type 5
In production since2007
Designed inChester, New York
Assembled inJapan
WarrantyLimited lifetime
ResaleHolds value strongly
Editor’s Take

At 82°, the edge disappears into your peripheral vision, and that, more than any number on the spec sheet, is the whole reason this eyepiece exists. Buy it once, and it stays your low-power eyepiece for life.

— The Skynocular verdict
10Alternatives

For a different goal, start here.

3 alternatives, each mapped to the goal it wins at
Widest true field

Tele Vue Panoptic 41 mm

A touch narrower apparent field (68°) but the widest TRUE field of any 2″ eyepiece, lighter and cheaper, too.

More immersion

Tele Vue Ethos 21 mm

100° of apparent field and more magnification, grander still, if you can carry (and afford) the extra glass.

Smaller & lighter

Tele Vue Nagler 26 mm T5

Nearly the same 82° experience with more reach, in a noticeably smaller and lighter body.

Community

Used in these setups.

Real builds from the community that include this product.

Star Cluster Sweeper

Featured

Ultra-wide-field setup for large star clusters and sweeping the Milky Way. The 80ED and the Panoptic 35mm give just under 4° of true field — wide enough to hold the Double Cluster, the Pleiades and long stretches of the summer Milky Way whole, at a 4.7mm exit pupil that stays comfortable under a dark sky. The Twilight I is a manual alt-azimuth on a steel tripod, which is exactly what sweeping wants: you push the scope along the star clouds and stop when something catches your eye.