Pentax XW 7mm — image 1
Pentax

Pentax XW 7mm

A planetary and lunar eyepiece built like a scientific instrument. Weather-sealed, tack-sharp, and with 20 mm of eye relief at 7 mm focal length, it makes high power feel effortless.

93/ 100
Polaris Score
Optical quality · Immersion · Comfort · Value
See the breakdown ↓
What it's for
Low power · wide fieldHigh power · narrow field

A high-power eyepiece for planets, the Moon, tight double stars and small planetary nebulae. Its 70-degree field is comfortable, but this is a detail instrument, not a wide-field sweeper, and it wants steady air.

Apparent Field
70°
Barrel Size
1.25"
Eye Relief
20mm
Focal Length
7mm
From$346

$30 above 90-day lowLast $316 in Jul 2026

Price tracked by PolarisObserved 120 timesTracking since Jun 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.

68° apparent field

At 70°, the black rim sits out at the corner of your attention rather than in front of you.
Try this eyepiece on your own scope in the Simulator →
01What it's good at

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

20 mm of eye relief at 7 mm focal length, letting you observe planets at high power without any eye strain, a rare combination.
Best at
✓20 mm of eye relief at 7 mm focal length, letting you observe planets at high power without any eye strain, a rare combination.
✓Weather-sealed and nitrogen-purged, so it shrugs off dew and cold that fogs lesser eyepieces mid-session.
✓Reference-grade sharpness and contrast on the Moon and planets, holding up against far pricier exotic glass.
Trade-offs
!Needs steady seeing to shine; on turbulent nights the high magnification just magnifies the boiling air.
!The 70-degree field is comfortable but won't immerse you like an 82 or 100-degree design.
!Premium price for a single high-power focal length.
02In your telescope

One eyepiece. A different job in every scope.

69× in a small refractor, 290× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 69× and 1.0° of sky in a little refractor, or 290× 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
69×
True field
1.0°
Exit pupil
1.3 mm
69x and a full degree in the little refractor, a surprisingly usable low-ish power here, sharp across the whole field.
8-inch Dobsonian
1200 mm · f/6
Magnification
171×
True field
25′
Exit pupil
1.2 mm
171x in the 8-inch Dob, right in the planetary sweet spot with a bright, comfortable 1.2 mm exit pupil.
12-inch Dobsonian
1500 mm · f/5
Magnification
214×
True field
20′
Exit pupil
1.4 mm
214x in the big Dob for serious lunar and planetary detail when the air cooperates.
8-inch SCT
2032 mm · f/10
Magnification
290×
True field
14′
Exit pupil
0.7 mm
290x out of the long SCT, high-power double-star and small-planetary-nebula work, with the seeing as the only limit.
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.

7mm FL · 70° AFOV · 1.25"
20 mm eye reliefExtraordinary at 7 mm
Effortless
At this short focal length most eyepieces force your eye against the glass; here you sit back and observe with glasses on.
Weather-sealed bodyBuilt to last
Dew-proof
Nitrogen-purged and sealed, so it resists the internal fogging that ends many high-power sessions early.
70° apparent fieldRoom to drift
Comfortable
Enough field that a planet doesn't shoot across the view in an undriven scope, without the bulk of an ultra-wide.
Steady-air dependentPhysics, not the glass
Wants calm skies
High power reveals the atmosphere as much as the target; save this eyepiece for the still nights.
04What comes alive

The targets this eyepiece was born for.

Jupiter, Saturn, The Moon, Mars at opposition, Double stars, Ring Nebula
JupiterComes alive
Jupiter
Belt structure, festoons and the Red Spot in a sharp, high-contrast, dew-proof high-power view.
SaturnComes alive
Saturn
Cassini Division, the crepe ring and subtle banding when the seeing steadies.
The MoonComes alive
The Moon
Rilles, crater chains and terraced walls at the terminator, comfortable to study for as long as you like.
Mars at oppositionExcellent
Mars at opposition
Polar cap and dark surface markings on the small disc, exactly the target this focal length is built for.
Excellent
Double stars
Tight pairs split cleanly on the sharp, high-contrast field.
Ring NebulaExcellent
Ring Nebula
Small planetary nebulae take high power well; the shell shows real structure at this scale.
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
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 mmThis one
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
Long SCT or Maksutov
High native focal length plus this eyepiece is a planetary specialist's pairing
8-inch and up reflector
Aperture plus steady air turns this into serious lunar and planetary resolution
Quality refractor
Its contrast rewards good optics; a clean apo and the XW is a lunar delight
Pair it
What extends its range
A 2x Barlow
Doubles the reach for the rare nights of exceptional seeing without buying a shorter eyepiece
A mid-power XW or Delos
Fills the workhorse slot so you can drop from finding to high power smoothly
Filter it
What transforms the view
Planetary colour filters
The high contrast base makes coloured filters more effective on belt and polar detail
Moon / neutral-density filter
Tames a bright gibbous Moon so you can study the terminator comfortably
07The Polaris Score

How it scores, and why.

93/100
93/ 100
Pentax XW 7mm

As a high-power detail eyepiece it is about as good as it gets: sharp, high-contrast, sealed against dew, and genuinely comfortable at a focal length where most eyepieces are a squint. It gives up almost nothing except price.

Optical quality
95
Immersion
83
Comfort
96
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.

You chase fine planetary and lunar detail and want it rendered sharply, with high contrast…
Buy it if you
✓You chase fine planetary and lunar detail and want it rendered sharply, with high contrast, on every good night.
✓You wear glasses or dislike jamming your eye into a short-focal-length lens; 20 mm of eye relief at 7 mm is remarkable.
✓You observe in dewy or cold conditions and value the weather-sealed, fog-resistant build.
✓You want a high-power eyepiece you can buy once and hand down.
Look elsewhere if you
!You mostly observe large, faint deep-sky objects at low power; that is the opposite end of the case from this.
!You observe from a location with poor seeing, where 200x-plus rarely holds and the eyepiece can't fix the atmosphere.
!You want the widest possible apparent field; 70 degrees is comfortable but not ultra-wide.
!You're on a budget, where a Celestron X-Cel 7mm delivers a genuinely good high-power view for a third of the cost.
09The numbers

Full specifications.

4 measured and stated values
Optical
Focal Length7mm
Apparent Field70°
Comfort & handling
Eye Relief20mm
Fit & build
Barrel Size1.25"
Editor’s Take

The XW line is what happens when an optics company that also makes binoculars and spotting scopes decides an eyepiece should survive dew, travel and a decade of hard use. It is the high-power eyepiece you stop thinking about, because it simply never gets in the way of the view.

— The Skynocular verdict
10Alternatives

For a different goal, start here.

3 alternatives, each mapped to the goal it wins at
The rival

Tele Vue Delos 6mm

The other 20 mm-eye-relief high-power reference, slightly wider at 72 degrees; the classic Pentax-versus-Tele-Vue call.

→
One step wider

Pentax XW 10mm

The same sealed, comfortable design a notch lower in power, for a larger exit pupil and easier nights.

Budget alternative

Celestron X-Cel LX 7mm

A genuinely good high-power view with comfortable eye relief for a third of the price, if the XW is a stretch.

→