Celestron Ultima Edge 18mm — image 1
Celestron

Celestron Ultima Edge 18mm

A 18mm Celestron Ultima Edge: a low-power eyepiece for framing large nebulae, galaxies and open clusters, from a flat-field 65-degree eyepiece that stays sharp to the edge in fast scopes.

80/ 100
Polaris Score
Optical quality · Immersion · Comfort · Value
See the breakdown ↓
What it's for
Low power · wide fieldHigh power · narrow field

Low power. At 18mm this is a low-power eyepiece for framing large nebulae, galaxies and open clusters; it is not the eyepiece for high-power planetary detail.

Apparent Field
65°
Barrel Size
1.25"
Eye Relief
16mm
Focal Length
18mm
From$169.95

Lowest in 90 daysLowest ever tracked

Price tracked by PolarisObserved 103 timesTracking since Jul 2026

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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. Widen the apparent field and watch the black edge of the eyepiece slip away.

65° apparent field

At 65°, you are aware of the field edge, like looking down a short, comfortable tube.
Try this eyepiece on your own scope in the Simulator →
01What it's good at

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

Comfortable 16mm eye relief across the line.
Best at
✓Comfortable 16mm eye relief across the line.
✓Compact and light for the field it delivers.
✓At 18mm it lands squarely in low power territory, exactly where wide star fields and large objects belong.
Trade-offs
!A 65-degree field, wider than a Plössl but short of a true ultra-wide.
!The lineup covers fewer focal lengths than the big modular ranges.
!Eyecup adjustment is basic.
02In your telescope

One eyepiece. A different job in every scope.

27× in a small refractor, 113× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 27× and 2.4° of sky in a little refractor, or 113× 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
27×
True field
2.4°
Exit pupil
3.3 mm
27× across a 2.4° field at a 3.3mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
8-inch Dobsonian
1200 mm · f/6
Magnification
67×
True field
58′
Exit pupil
3.0 mm
67× across a 58′ field at a 3mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
12-inch Dobsonian
1500 mm · f/5
Magnification
83×
True field
47′
Exit pupil
3.6 mm
83× across a 47′ field at a 3.6mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
8-inch SCT
2032 mm · f/10
Magnification
113×
True field
35′
Exit pupil
1.8 mm
113× across a 35′ field at a 1.8mm exit pupil, crisp medium power for galaxies, clusters and planetary nebulae.
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.

18mm FL · 65° AFOV · 1.25"
Focal lengthLow to mid power
18mm
About 67x in an 8 inch f/5.9 Dobsonian and 113x in an 8 inch SCT. Comfortable for finding objects and still high enough to show structure once you have them centred.
Apparent fieldWide
65°
At this focal length a 65 degree field gives a true field wide enough to frame most open clusters whole, which makes it a practical main eyepiece for a deep-sky session.
Eye reliefComfortable
16mm
Enough room for relaxed viewing and thin glasses. Consistent eye relief across the range means switching eyepieces does not force you to relearn your eye position.
BarrelStandard
1.25"
Fits any telescope without adapters. At 18 mm and 65 degrees the field stop still sits within what the 1.25 inch format passes comfortably.
OpticsFlat field
Fully multi-coated
A flat-field design with full coatings, so stars stay tight toward the edge and contrast holds up. It is the sensible choice when your telescope is fast and premium eyepieces are out of budget.
04What comes alive

The targets this eyepiece was born for.

The Orion Nebula (M42), The Andromeda Galaxy (M31), The Pleiades (M45), The Double Cluster…
The Orion Nebula (M42)Comes alive
The Orion Nebula (M42)
Wings of nebulosity fill the field with the Trapezium embedded.
The Andromeda Galaxy (M31)Excellent
The Andromeda Galaxy (M31)
The bright core with its two companion galaxies framed.
The Pleiades (M45)Excellent
The Pleiades (M45)
The whole cluster with dark sky to spare around it.
The Double ClusterComes alive
The Double Cluster
Two open clusters glittering side by side in one view.
The Beehive (M44)Excellent
The Beehive (M44)
A loose scatter of bright stars, best at low power.
Large open clustersExcellent
Large open clusters
Bright, wide targets that want field, not magnification.
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.

32 mm
Low power · wide field
Find, frame and sweep. Your widest true field and the lowest useful magnification, the eyepiece you reach for first.
Veil Nebula · Pleiades · Milky Way star clouds
18 mmThis one
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 · Pair it · Filter it
The telescope
What it goes into
Any 1.25-inch focuser
Fits essentially every telescope made.
Fast, short scopes love this field
A fast Newtonian or refractor turns this focal length into a rich, wide sweep.
Pair it
What extends its range
A high-power eyepiece (~11mm)
Locate and frame with this one, then swap to high power for planets and small objects.
Filter it
What transforms the view
A UHC or OIII nebula filter
At low power this eyepiece frames big emission nebulae; a narrowband filter makes the Veil and North America jump out.
07The Polaris Score

How it scores, and why.

80/100
80/ 100
Celestron Ultima Edge 18mm

Judged as a low-power eyepiece for framing large nebulae, galaxies and open clusters, it earns its score on a genuinely flat field: sharp corner to corner, even in f/5 newtonians. The comfortable eye relief lifts it further. A wide field is what this focal length is for, and it delivers.

Optical quality
80
Immersion
75
Comfort
84
Value
82

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.

Observers who want a low-power eyepiece for framing large nebulae, galaxies and open…
Buy it if you
✓Observers who want a low-power eyepiece for framing large nebulae, galaxies and open clusters.
✓Anyone who observes in eyeglasses; the eye relief here is long enough to see the whole field.
✓Observers who value on-axis contrast over a sprawling field.
Look elsewhere if you
!Anyone chasing the absolute widest field, who should look at a 100-degree eyepiece.
!Grab-and-go observers watching every gram, since this is not the lightest option.
!Planetary specialists who want the last ounce of high-power contrast from an orthoscopic.
09The numbers

Full specifications.

4 measured and stated values
Optical
Focal Length18mm
Apparent Field65°
Comfort & handling
Eye Relief16mm
Fit & build
Barrel Size1.25"
Editor’s Take

Sweep it across a rich star field and the reason to own this focal length is obvious in a second. That is what the Ultima Edge is for.

— The Skynocular verdict
10Alternatives

For a different goal, start here.

3 alternatives, each mapped to the goal it wins at
Wider, lower power

Celestron Ultima Edge 30mm

The same optics with more true field, for framing larger objects and finding your way around.

→
More magnification

Celestron Ultima Edge 10mm

The same line at higher power, for planets and the smallest deep-sky detail.

→
Cross-shop

Tele Vue Panoptic

A natural alternative at a nearby price point, if you want to compare field and feel before committing.

→