Apertura Panorama 21mm — image 1
Apertura

Apertura Panorama 21mm

A 21mm Apertura Panorama: a low-power eyepiece for framing large nebulae, galaxies and open clusters, from a value 82-degree ultra-wide that delivers the big field without the premium price.

84/ 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 21mm 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
82°
Barrel Size
2"
Eye Relief
15mm
Focal Length
21mm
From$229.95

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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.

82° apparent field

At 82°, the edge slips into your peripheral vision, you stop looking at a field and start looking into the sky.
Try this eyepiece on your own scope in the Simulator →
01What it's good at

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

15mm of eye relief and a large eye lens for an easy, immersive view.
Best at
✓15mm of eye relief and a large eye lens for an easy, immersive view.
✓Threaded for filters and solidly built.
✓At 21mm it lands squarely in low power territory, exactly where wide star fields and large objects belong.
Trade-offs
!Some edge softening in fast scopes, as with most value ultra-wides.
!Heavy in the longer 2-inch focal lengths.
!On-axis it is very good but not premium-sharp.
02In your telescope

One eyepiece. A different job in every scope.

23× in a small refractor, 97× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 23× and 3.6° of sky in a little refractor, or 97× 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
23×
True field
3.6°
Exit pupil
3.8 mm
23× across a 3.6° field at a 3.8mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
8-inch Dobsonian
1200 mm · f/6
Magnification
57×
True field
1.4°
Exit pupil
3.5 mm
57× across a 1.4° field at a 3.5mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
12-inch Dobsonian
1500 mm · f/5
Magnification
71×
True field
1.2°
Exit pupil
4.2 mm
71× across a 1.2° field at a 4.2mm exit pupil, a bright, low-power sweep for framing the largest objects.
8-inch SCT
2032 mm · f/10
Magnification
97×
True field
51′
Exit pupil
2.1 mm
97× across a 51′ field at a 2.1mm exit pupil, right in the deep-sky sweet spot, bright and easy on the eye.
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.

21mm FL · 82° AFOV · 2"
Focal lengthLow to mid power
21mm
Around 57x in an 8 inch f/5.9 Dobsonian and 97x in an 8 inch SCT. Low enough to find and frame large objects, high enough to keep the sky background dark, which is the balance most observers use for the bulk of a session.
Apparent fieldVery wide
82°
At this focal length the 82 degree field yields a true field wide enough to hold the whole Veil complex or the Pleiades with room to spare. Wide true fields are the reason to combine a long focal length with a wide apparent field.
Eye reliefComfortable
15mm
Comfortable without glasses, tight with them. At low power that matters slightly less, because you are more likely to be scanning than studying a fixed point.
BarrelRequires 2 inch focuser
2"
A 2 inch barrel is needed to pass the field stop that 82 degrees at 21 mm demands, so confirm your telescope has a 2 inch focuser or diagonal before buying. A 1.25 inch adapter would clip the very field you paid for.
OpticsValue wide-field
Fully multi-coated
Full multi-coating keeps transmission high through a long, complex optical train. Expect good centre sharpness with some field curvature at the edges in fast telescopes, which is the honest limit of this price class.
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.

21 mmThis one
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
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 · Pair it · Filter it
The telescope
What it goes into
Any 2-inch focuser
A 2-inch focuser or a 1.25-inch adapter; most Dobsonians and larger refractors qualify.
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 (~13mm)
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.

84/100
84/ 100
Apertura Panorama 21mm

Judged as a low-power eyepiece for framing large nebulae, galaxies and open clusters, it earns its score on a true 82-degree field at a mid-range price. The comfortable eye relief lifts it further. A wide field is what this focal length is for, and it delivers.

Optical quality
79
Immersion
93
Comfort
84
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.

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.
✓Deep-sky observers chasing the most immersive, wrap-around field they can get at this price.
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 Length21mm
Apparent Field82°
Comfort & handling
Eye Relief15mm
Fit & build
Barrel Size2"
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 Panorama is for.

— The Skynocular verdict
10Alternatives

For a different goal, start here.

2 alternatives, each mapped to the goal it wins at
More magnification

Apertura Panorama 10mm

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

→
Cross-shop

Celestron Luminos

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

→