Apertura Plössl 15mm — image 1
Apertura

Apertura Plössl 15mm

A 15mm Apertura Plössl: the workhorse magnification where most galaxies, globulars and nebulae look their best, from an honest, sharp 52-degree Plössl at the lowest sensible price.

71/ 100
Polaris Score
Optical quality · Immersion · Comfort · Value
See the breakdown ↓
What it's for
Low power · wide fieldHigh power · narrow field

Medium power. At 15mm this is the workhorse magnification where most galaxies, globulars and nebulae look their best.

Apparent Field
52°
Barrel Size
1.25"
Eye Relief
11mm
Focal Length
15mm
From$29.95

Lowest in 90 daysLowest ever tracked

Price tracked by PolarisObserved 20 timesTracking since Mar 2026

Try in simulator →
Where to buy

Verified yesterday · prices tracked daily

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.

50° apparent field

At 52°, 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.

Cheap enough to own several and cover a whole range of magnifications.
Best at
✓Cheap enough to own several and cover a whole range of magnifications.
✓Classic four-element Plössl optics: crisp and high-contrast on-axis.
✓At 15mm it lands squarely in medium power territory, exactly where most deep-sky objects look their best.
Trade-offs
!Very short eye relief below about 10mm, which is genuinely uncomfortable.
!A 52-degree field is narrow by modern standards.
!Simple coatings and build; this is a value tool, not a showpiece.
02In your telescope

One eyepiece. A different job in every scope.

32× in a small refractor, 135× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 32× and 1.6° of sky in a little refractor, or 135× 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
32×
True field
1.6°
Exit pupil
2.7 mm
32× across a 1.6° field at a 2.7mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
8-inch Dobsonian
1200 mm · f/6
Magnification
80×
True field
39′
Exit pupil
2.5 mm
80× across a 39′ field at a 2.5mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
12-inch Dobsonian
1500 mm · f/5
Magnification
100×
True field
31′
Exit pupil
3.0 mm
100× across a 31′ field at a 3mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
8-inch SCT
2032 mm · f/10
Magnification
135×
True field
23′
Exit pupil
1.5 mm
135× across a 23′ field at a 1.5mm 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.

15mm FL · 52° AFOV · 1.25"
Focal lengthMedium power
15 mm
This works out at 32x in a small refractor, 80x in an eight inch Dobsonian and 135x in an eight inch Schmidt-Cassegrain. That middle range is the most used setting in most kits: enough magnification to show structure in globular clusters and planetary nebulae, and not so much that finding the target becomes a chore.
Apparent fieldTraditional
52°
Fifty two degrees is the classic Plossl field, and it is narrower than the modern wide-field designs by a visible margin. The practical consequence is drift: in an eight inch Dobsonian this frames about 39 arcminutes, so on an undriven mount an object crosses the view and needs nudging back roughly every 3 minute or so.
Eye reliefAdequate
11 mm
At 11 millimetres your eye needs to sit fairly close, and spectacle wearers will lose the field edge. A Plossl's eye relief is roughly seven tenths of its focal length, so this is the design working as intended rather than a fault, and it is the reason the shorter Plossls are less pleasant than the longer ones.
Optical designSimple and sharp
4-element Plössl
Four elements in two cemented pairs, which is the arrangement that has defined this eyepiece type since the 1860s. It is sharp on axis, colour neutral and cheap to make well. What it does not do is hold the field flat: in a telescope faster than about f/6 the outer fifth of the view softens visibly, which is the difference between this and the flat-field designs that cost three times as much.
BarrelUniversal
1.25 inch
Fits the 1.25 inch focuser on virtually every telescope made, which is the format's whole advantage. Nothing about this eyepiece requires an adapter, a 2 inch diagonal or a specific focuser, so it works in a beginner refractor and in a large Dobsonian without any thought.
04What comes alive

The targets this eyepiece was born for.

M13 globular cluster, The Whirlpool (M51), The Dumbbell Nebula (M27), M81 and M82, The Ring…
M13 globular clusterComes alive
M13 globular cluster
Resolves to the core with pinpoint stars across the field.
The Whirlpool (M51)Excellent
The Whirlpool (M51)
Two cores and a hint of the bridging spiral arm.
The Dumbbell Nebula (M27)Comes alive
The Dumbbell Nebula (M27)
The apple-core shape framed with dark sky around it.
M81 and M82Excellent
M81 and M82
Both galaxies in one field, one soft, one edge-on and streaky.
The Ring Nebula (M57)Excellent
The Ring Nebula (M57)
A clean smoke ring at a comfortable scale.
The Trapezium in OrionExcellent
The Trapezium in Orion
Four stars split cleanly inside the glowing nebula.
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
15 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 (~9mm)
Locate and frame with this one, then swap to high power for planets and small objects.
Filter it
What transforms the view
A mild broadband light-pollution filter
Lifts contrast on galaxies and clusters from the suburbs at medium power.
07The Polaris Score

How it scores, and why.

71/100
71/ 100
Apertura Plössl 15mm

Judged as the workhorse magnification where most galaxies, globulars and nebulae look their best, it earns its score on classic four-element plössl optics: crisp and high-contrast on-axis. Tighter eye relief at this focal length is the main thing holding it back. It is honest about being a specialist, not an all-rounder.

Optical quality
70
Immersion
60
Comfort
68
Value
88

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 the workhorse magnification where most galaxies, globulars and nebulae…
Buy it if you
✓Observers who want the workhorse magnification where most galaxies, globulars and nebulae look their best.
✓Observers happy to take their glasses off at the eyepiece.
✓Observers who value on-axis contrast over a sprawling field.
Look elsewhere if you
!Anyone who has looked through a wide-field eyepiece and cannot go back to a 52-degree tunnel.
!Eyeglass wearers, who will not comfortably reach the full field at this focal length.
!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 Length15mm
Apparent Field52°
Comfort & handling
Eye Relief11mm
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 Plössl 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

Apertura Plössl 24mm

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

More magnification

Apertura Plössl 9mm

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

→
Cross-shop

Celestron X-Cel LX

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

→