Explore Scientific 82° Series LER 6.5mm Waterproof Eyepiece

Product Overview

The Explore Scientific 82° Series LER 6.5mm is a high-magnification eyepiece built around one uncommon combination: an 82° apparent field and 16.8mm of eye relief in the same 1.25-inch body. Short focal lengths normally trade eye relief away first, and LER stands for the long eye relief that this design keeps instead.

The published figures are 6.5mm focal length, 16.8mm eye relief, a body 106mm long and 50mm wide, and a weight of 11.5oz (325g) in a 1.25-inch barrel. Explore Scientific specifies low-dispersion glass with multi-coated lenses in an argon-purged, O-ring sealed housing.

At 6.5mm this is firmly a high-power eyepiece. In a 663mm refractor it gives 102x; in a 1219mm Dobsonian, 188x; in a 2000mm Schmidt-Cassegrain, 308x. The 82° field is what makes that magnification comfortable rather than claustrophobic — an object at high power sits inside a wide surround instead of filling a tunnel.

Who It's For

• Lunar and planetary observers: 6.5mm is a working high-power focal length in most apertures, and low-dispersion glass is aimed at exactly the colour and contrast that fine planetary detail depends on.
• Double-star observers who want magnification without a field so narrow the pair drifts out between looks.
• Eyeglass wearers observing at high power: 16.8mm at 6.5mm focal length is the whole point of the LER designation, and it is unusual at this end of the range.
• Dobsonian owners: an 82° field at high power buys real drift time on an undriven mount, where a narrow field would need nudging every few seconds.
• Observers of compact deep-sky targets — planetary nebulae, globular cluster cores, small bright galaxies — where magnification darkens the sky background and pulls detail out.

Key Features & Design

• 16.8mm eye relief at 6.5mm focal length: the defining specification of the LER line, and the reason this eyepiece is usable with glasses at magnifications where most designs are not.
• 82° apparent field: ultra-wide, which at high power translates directly into how long an object stays in view and how much context surrounds it.
• Low-dispersion glass with multi-coated lenses: low-dispersion elements bring wavelengths closer to a common focus inside the eyepiece, which shows as cleaner colour edges and better contrast on bright planetary detail.
• Argon purged and O-ring sealed: argon inside the housing does not condense the way trapped humid air does, so the internal surfaces stay clear as the temperature drops.
• 1.25″ barrel: fits any standard 1.25-inch focuser or diagonal.
• 106mm long and 50mm wide: a tall eyepiece for its barrel size, which is what an 82° field with 16.8mm of eye relief takes in glass.
• 11.5oz (325g) published weight, substantial for a 1.25-inch eyepiece and worth knowing before it goes into a Dobsonian focuser.

Recommended Uses

• High-power lunar observing — crater floors, rilles and the terminator.
• Planetary detail on Jupiter, Saturn and Mars when the atmosphere is steady.
• Splitting close double stars.
• High-power observing on a manual altazimuth or Dobsonian mount, where the 82° field is what makes it practical.

Compatibility and Accessory Notes

• Fits any 1.25-inch focuser or diagonal. In a 2-inch focuser it takes a 2-inch to 1.25-inch adapter.
• Magnification: telescope focal length ÷ 6.5. A 663mm refractor gives 102x, a 1219mm Dobsonian 188x, a 1500mm Maksutov 231x, a 2000mm Schmidt-Cassegrain 308x.
• Exit pupil: 6.5 ÷ the telescope's focal ratio. An f/5.9 Dobsonian gives 1.1mm, an f/6.5 refractor 1.0mm, an f/10 Schmidt-Cassegrain 0.65mm. Small exit pupils are normal at high power and are what make the sky background go dark.
• Filters: takes standard 1.25-inch threaded filters. Colour and neutral-density filters are the usual companions for planetary and lunar work at this magnification.
• Balance: 325g is heavy for a 1.25-inch eyepiece. On a Dobsonian or a small refractor, expect to recheck balance when swapping into it, and the same when swapping out.
• Focuser clearance: the body is 106mm long. In a short drawtube or a shallow eyepiece case, that dimension is worth checking against what you have.
• Focal extenders: pairing an extender with a 6.5mm pushes past the useful magnification of most apertures. Longer focal lengths in the range are the better partner for an extender.

Good to Know Before You Order

• Seeing conditions govern a 6.5mm eyepiece. On a steady night in a six-inch or larger telescope it will show what the aperture can resolve; on a turbulent night a longer focal length will show more. That is atmosphere rather than optics, and it is why most observers keep both.
• Explore Scientific does not publish the field stop diameter, the element count or a coating specification for this eyepiece. Those rows read as not published below rather than being estimated. Without a field stop figure the true field cannot be calculated exactly, so we are not going to quote one — if it matters to you, we will ask our Explore Scientific representative.
• Explore Scientific does not list the box contents for this model either, so we are not stating which caps or accessories are included. We can confirm that before it ships if you would like to know.
• It is a heavy 1.25-inch eyepiece at 325g and 106mm long. Focusers with a light compression ring hold it fine, but balance on an undriven mount shifts noticeably when it goes in. A Dobsonian with adjustable tension handles that without fuss.
• 16.8mm of eye relief means the eye sits further back than usual, which takes a session or two to get used to if you are coming from a short-relief planetary eyepiece. Once the eyecup height is set to suit you it holds.

Frequently Asked Questions

Is it difficult to set up?

No — it drops into any 1.25-inch focuser or diagonal and works immediately. There is nothing to assemble or adjust beyond setting the eyecup where it suits your eye.

What magnification will I get?

Divide your telescope's focal length in millimetres by 6.5. A 1000mm telescope gives 154x; a 1219mm Dobsonian gives 188x.

What does LER mean here?

Long eye relief. The published figure is 16.8mm, which at a 6.5mm focal length is unusual — short eyepieces normally place the eye very close to the lens. It is what makes high-power observing with glasses on, or simply for long stretches, comfortable.

Can I use it with glasses on?

Yes. 16.8mm is enough for most spectacle wearers to take in the field, which is the specific problem this design sets out to solve.

Is 6.5mm too much magnification for my telescope?

It depends on aperture and on the night. As a rule of thumb the atmosphere supports around twice the aperture in millimetres as a maximum useful magnification, so a 150mm telescope tops out near 300x on its best nights. At 6.5mm you reach 231x in a 1500mm telescope, which is inside that on a good night and beyond it on a poor one. Send us your telescope's aperture and focal length and we will tell you where this lands.

How does it compare to the 82° Series without LER?

The apparent field is the same 82°. What the LER design puts first is eye relief at short focal lengths, which is where the standard approach usually gives ground. If eye comfort at high power is what you are solving for, that is the difference.

Bottom Line

In short: a 6.5mm high-power eyepiece with an 82° apparent field and 16.8mm of eye relief, in a 325g argon-purged 1.25-inch body with low-dispersion multi-coated glass — ultra-wide field and an unusually comfortable eye position at magnifications where both are normally hard to get. Tell us your telescope's focal length and we will confirm what power it gives you and how it sits alongside the eyepieces you already have.