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 low

Price tracked by PolarisObserved 72 timesTracking since Jun 2026

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Where to buy

Agena AstroProductsPartnerBest price$346→Astronomics$346→

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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.

See this field in your own scope in the Simulator →

01What it's good at

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

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.

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.

02In plain English

The numbers, in plain English.

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.

03What comes alive

The targets this eyepiece was born for.

Comes alive

Jupiter

Belt structure, festoons and the Red Spot in a sharp, high-contrast, dew-proof high-power view.

Comes alive

Saturn

Cassini Division, the crepe ring and subtle banding when the seeing steadies.

Comes alive

The Moon

Rilles, crater chains and terraced walls at the terminator, comfortable to study for as long as you like.

Excellent

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.

Excellent

Ring Nebula

Small planetary nebulae take high power well; the shell shows real structure at this scale.

04Role in a collection

Where it sits in your eyepiece case.

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

04Build around it

What it pairs with.

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

02The Polaris Score

How it scores, and why.

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

Immersion

Comfort

Value

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

03Who it's for

An honest fit check.

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.

05The numbers

Full specifications.

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

06Alternatives

For a different goal, start here.

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.

→

Pentax XW 7mm

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

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

One eyepiece. A different job in every scope.

The numbers, in plain English.

The targets this eyepiece was born for.

Where it sits in your eyepiece case.

What it pairs with.

How it scores, and why.

An honest fit check.

Full specifications.

For a different goal, start here.

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