Explore Scientific 62° Series 9mm Waterproof Eyepiece

Product Overview

The Explore Scientific 62° Series 9mm is an argon-purged waterproof eyepiece with a 1.25-inch barrel, 12.6mm of eye relief and a published body size of 57mm long by 38mm wide. At 9mm it sits toward the high-power end of a general-purpose focal-length set: 79x in a 714mm refractor, 111x in a 1000mm telescope, 133x in a 1200mm Schmidt-Cassegrain.

Explore Scientific specifies the 62° Series as a flat-field, multi-element design with contrast good enough to support averted vision on faint targets, and describes the series as near-parfocal — swapping between focal lengths in the range asks for little more than a touch on the focuser rather than a full refocus.

62 degrees is a comfortable apparent field. It is wider than a Plössl's 50 degrees by enough to notice, without pushing the eye position or the outer-field demands that 82° and 100° designs bring.

Who It's For

• Lunar and planetary observers: 9mm is the focal length that turns most telescopes into planetary instruments, and the flat field keeps detail crisp when the object drifts off centre.
• Double-star observers: enough magnification to open moderately close pairs, with 12.6mm of eye relief so the eye can hold position through a careful look.
• Observers building a matched set: the near-parfocal design across the 62° Series means changing power costs a small focus tweak rather than a hunt.
• Observers working in dew and damp air: the argon-purged, sealed body is built for conditions that fog a conventional eyepiece.
• Users of compact telescopes: a 57mm x 38mm body is small and light enough that it will not upset the balance of a short tube or a small alt-azimuth head.

Key Features & Design

• 9mm focal length: the workhorse high-power step in most eyepiece sets, sitting between medium-power scanning and the very short focal lengths that only good seeing supports.
• 62° apparent field of view: a step up in immersion from a Plössl, and an easier outer field than the wide-angle series.
• Argon-purged and sealed: the inert fill displaces the moisture-bearing air that condenses inside an unsealed eyepiece when temperatures drop.
• Flat-field multi-element design specified by Explore Scientific, aimed at sharpness that holds from the centre of the field outward.
• 12.6mm eye relief: published for this focal length, which is generous compared with a 9mm Plössl where eye relief scales down with focal length.
• Near-parfocal within the series, so a change of magnification is close to a straight swap.
• 1.25-inch barrel with a standard filter thread.
• 57mm long, 38mm wide: the published body dimensions.

Recommended Uses

• High-power lunar work along the terminator, where craterlets and rilles reward magnification.
• Planetary detail — Jovian belt structure, Saturn's ring division, Martian albedo features at opposition.
• Splitting double stars of moderate separation.
• Compact deep-sky targets: planetary nebulae, globular cluster cores, small bright galaxies.
• Damp-site and coastal observing where a sealed housing keeps the session going.

Compatibility and Accessory Notes

• Fits any 1.25-inch focuser or diagonal directly. A 2-inch focuser takes it with a 2-inch to 1.25-inch adapter, which most 2-inch diagonals already include.
• Magnification: telescope focal length ÷ 9. A 500mm reflector gives 56x, a 714mm refractor 79x, a 1200mm SCT 133x, a 2000mm SCT 222x.
• True field: Explore Scientific does not publish a field stop diameter for this eyepiece, so the true field is approximated as 62° divided by the magnification — about 0.56° at 111x.
• Filters: the barrel takes standard 1.25-inch threaded filters. A lunar or neutral-density filter pairs naturally with 9mm on a bright Moon.
• Focal extenders: a 2x extender turns this into an effective 4.5mm, which in a long-focus telescope reaches magnifications that only steady nights support.
• Within the series: the near-parfocal design means a 9mm and a longer 62° eyepiece can be exchanged mid-session with minimal refocusing.

Good to Know Before You Order

• Explore Scientific does not publish a weight, element count or field stop diameter for this eyepiece — the weight cell on their own spec table is blank. Those rows read as not published below rather than carrying an estimate. If one of them decides the purchase, ask us and we will put the question to our Explore Scientific rep.
• 12.6mm of eye relief is workable rather than generous. Most observers find it comfortable with the eyecup up; for observing with glasses on, the 72° ED Series carries more eye relief and we stock it.
• At 9mm the exit pupil is small. In an f/10 telescope it is 0.9mm, which is where floaters in your own eye can start to become visible — a normal effect of high magnification rather than anything happening in the optics.
• The 62° field is moderate by design. If a broad, immersive view is what you are after, the 82° and 100° Series cover that ground; the 62° Series is built around flat-field sharpness and value.
• Waterproofing covers immersion, not use underwater. The sealed, argon-filled housing is there so heavy dew, rain and a drop into wet grass are non-events.

Frequently Asked Questions

Is it difficult to set up?

No — it drops into any 1.25-inch focuser or diagonal and is ready to observe with. There is nothing to assemble, align or adjust.

What magnification will I get?

Divide your telescope's focal length in millimetres by 9. A 1000mm telescope gives 111x; a 1500mm Maksutov gives 167x.

What does argon purging change?

Argon is inert and carries no moisture, so once the housing is sealed with it there is nothing inside to condense on the internal lens surfaces when the eyepiece cools. Sealed air would fog.

Can I use filters with it?

Yes. Standard 1.25-inch threaded filters screw into the bottom of the barrel — lunar, neutral density, colour and narrowband alike.

How does it compare with a 9mm Plössl?

A wider apparent field at 62° against roughly 50°, a flat-field multi-element design, more eye relief than a 9mm Plössl typically offers, and a sealed argon-purged body. The differences show most at the field edge and in damp conditions.

Will it work in my Dobsonian?

Yes, in any 1.25-inch focuser. On an undriven mount 9mm produces enough magnification that objects cross the field fairly quickly, so the 62° field is doing useful work buying drift time.

Bottom Line

In short: a sealed, argon-purged 9mm eyepiece with a flat 62° field, 12.6mm of eye relief and a 1.25-inch filter-threaded barrel, in a compact 57 x 38mm body — a high-power focal length that stays comfortable and holds sharpness across the field. If you would like help working out which focal lengths would round out your set, send us your telescope's aperture and focal length and we will map it out with you.