Explore Scientific 82° Series 30mm Waterproof Eyepiece

Product Overview

The Explore Scientific 82° Series 30mm is the low-power, wide-field end of the 82° range, built on a 2-inch barrel with an argon-purged waterproof housing. It carries a published 43mm field stop, 22mm of eye relief and an 82° apparent field, and measures 131mm long by 82mm wide at 35.5oz (1007g). It is a substantial piece of glass, and the size is a direct consequence of what it does.

43mm is essentially the largest field stop a 2-inch barrel can pass, which means this eyepiece delivers about as much true field as the 2-inch format physically allows. In a 952mm refractor that works out to 2.6°; in a 1200mm Schmidt-Cassegrain, 2.05°; in a 1500mm Maksutov, 1.64°. Magnification is modest by design — 32x in that 952mm refractor — and the point is the amount of sky in view, not the size of what is in it.

Explore Scientific specifies precision-machined metal barrels, low-dispersion optical glass, enhanced multi-layer deposition coatings and flat black internal surfaces to suppress scatter. The 22mm of eye relief is generous for any eyepiece and unusual in one with this much apparent field.

Who It's For

• Rich-field observers: a 43mm field stop is the widest true field a 2-inch eyepiece can give, which is what makes large open clusters, the Veil, the Andromeda halo and the great nebulae fit as objects rather than fragments.
• Dobsonian owners: low power plus 82° of apparent field means an object crosses the view slowly, and the combination is about as forgiving as manual tracking gets.
• Eyeglass wearers: 22mm of eye relief is enough to take in a large part of an 82° field with glasses on.
• Damp-climate observers: the argon-purged sealed body is built for dew-heavy sites and cold, humid nights.

Key Features & Design

• 82° apparent field of view: the immersive end of the range, where the field edge sits outside your comfortable direct vision and the view feels like a window rather than a tube.
• 43mm field stop: published, and about the physical limit of what a 2-inch barrel can pass. This is the number that sets the true field.
• 22mm eye relief: generous, and unusually so for a wide-field eyepiece.
• 2″ barrel: required to carry a field stop this large, and standard on any 2-inch focuser or diagonal.
• Low-dispersion optical glass in the design, aimed at colour fidelity across a very wide field.
• Enhanced multi-layer deposition (EMD) coatings: raise transmission and hold contrast, which matters most on the faint extended objects this focal length is built to frame.
• Flat black internal surfaces to minimise light scatter inside the barrel.
• Argon-purged, sealed waterproof construction: inert gas in place of moist air, so internal fogging is not a failure mode.

Recommended Uses

• Wide-field deep-sky sweeping — the Milky Way, large open clusters, extended nebulae and star fields.
• Framing large objects that overflow a narrower field: the Veil, the North America Nebula, the Pleiades, M31 with its companions.
• Low-power finding and identification before switching to a high-power eyepiece.
• Manual Dobsonian observing, where low power and a wide apparent field together minimise nudging.

Compatibility and Accessory Notes

• 2-inch focuser or diagonal required. The 43mm field stop is what makes the 2-inch format necessary — a 1.25-inch barrel physically cannot pass this much field. If your telescope has a 1.25-inch focuser only, we can advise on whether a 2-inch upgrade is available for it.
• Magnification: telescope focal length ÷ 30. A 750mm Newtonian gives 25x; a 952mm refractor 32x; a 1200mm SCT 40x; a 2000mm SCT 67x.
• True field: 43mm ÷ telescope focal length × 57.3. A 750mm scope gives 3.3°; a 1200mm gives 2.05°.
• Exit pupil: 30mm divided by your telescope's focal ratio. At f/5 that is 6mm, at f/10 it is 3mm. In telescopes slower than about f/6 the exit pupil stays within what a dark-adapted eye can use comfortably; in very fast instruments some of the light cone can fall outside the pupil at this focal length.
• Filters: takes 2-inch threaded filters, which screw into the bottom of the barrel. A UHC or O-III filter in front of a 30mm at 82° is one of the great combinations in visual deep-sky observing.
• Focal extenders: Explore Scientific designs its focal extenders to work with this series, raising magnification while preserving the native field and eye relief characteristics of the eyepiece.
• Balance: at 35.5oz this eyepiece shifts the balance of a small refractor or a Dobsonian noticeably. Counterweights and adjustable tube rings solve it, and we can suggest what suits your telescope.

Good to Know Before You Order

• It weighs 35.5oz (1007g). That is enough to swing a Dobsonian out of balance or to tip a light refractor on an undersized mount. Counterweights and rebalancing solve it, and we stock the parts — tell us your telescope and we will suggest the simplest fix.
• It needs a 2-inch focuser or diagonal. There is no adapter route from a 43mm field stop into a 1.25-inch barrel, since the barrel itself is the limit. Many telescopes can be upgraded to a 2-inch focuser, and we can tell you whether yours is one of them.
• Low power is the point. At 30mm this eyepiece frames wide fields; planetary detail and close double stars call for a much shorter focal length, and the 82° Series covers those too.
• Explore Scientific does not publish an element count or the box contents for this eyepiece, so those rows read as unpublished below. If either is important to you, ask and we will check with our Explore Scientific rep.

Frequently Asked Questions

Is it difficult to set up?

No — it slides into any 2-inch focuser or diagonal and is ready to use, with nothing to assemble or adjust. The one practical consideration is its weight: at 35.5oz it is worth rebalancing the telescope after inserting it, particularly on a Dobsonian or a small refractor.

Can I use it in a 1.25-inch focuser?

No — the 43mm field stop needs the full 2-inch barrel. If your telescope is 1.25-inch only, send us the model and we will let you know whether a 2-inch focuser upgrade exists for it.

How wide is the actual view?

Divide the 43mm field stop by your telescope's focal length and multiply by 57.3. A 1000mm telescope gives 2.46°, or about five full-Moon widths.

Can I use it with glasses on?

22mm of eye relief is generous and makes that workable. With an 82° field, the outermost edge is easier to reach with glasses off, but most of the field is available either way.

Will it work with a focal extender?

Yes. Explore Scientific designs its focal extenders to work with this series, increasing magnification while keeping the eyepiece's native field and eye relief behaviour intact.

Bottom Line

In short: a 30mm eyepiece with an 82° apparent field, a 43mm field stop at the practical limit of the 2-inch format, 22mm of eye relief and an argon-purged waterproof body — the widest true field a 2-inch eyepiece can deliver, in a 35.5oz package that earns the space it takes. If you would like a hand working out whether your telescope's focuser and balance will take it comfortably, send us the model and we will go through it with you.