Explore Scientific 92° ED Series 9mm Waterproof Eyepiece (2")

High power with a 92° window on the sky

The Explore Scientific 92° ED Series 9mm Waterproof Eyepiece is the high-power member of the series, for planets, globular clusters and small nebulae, with a field wide enough that objects stay in view longer on a mount without tracking. It has a 92° apparent field, a 2" barrel, 18mm of eye relief and a 13.5mm field stop, and its 9 elements in 6 groups include H-FK61 ED glass to keep color fringing low and contrast high. Explore Scientific builds the series to be waterproof.

Key specs: 9mm focal length · 92° apparent field · 2" barrel · 18mm eye relief · 13.5mm field stop · 9 elements in 6 groups · H-FK61 ED glass · waterproof

What you'll see

• Planets: Jupiter's belts and moons and Saturn's rings, with plenty of room before they drift out of view in a Dobsonian.
• Globular clusters: M13, M92 and M5 resolved toward their cores, framed by dark sky.
• Small nebulae: the Ring Nebula, the Cat's Eye Nebula and the Eskimo Nebula.

In an 8" Dobsonian (1200mm) the 9mm gives 133x and a 0.64° true field. In an 80mm f/6 refractor (480mm) it gives 53x and a 1.61° field. For comparison, the full Moon is about 0.5° across.

Why the 92° ED series

• A field you look into, not through: at 92° the edge of the view sits at the edge of your vision, so the eyepiece's field stop seems to disappear. On a Dobsonian or other undriven mount, objects also take longer to drift out of view.
• ED glass: an H-FK61 fluorophosphate element (Abbe number 81.6) reduces color fringing on bright stars, the Moon and planets. Coatings are multi-layer.
• 18mm eye relief: comfortable for most eyeglass wearers, which is rare in fields this wide.
• Waterproof: dew and damp nights are less of a worry, and the eyepiece is easier to keep clean.

What to add for the best results

• A 2" diagonal or focuser (required): refractors and Schmidt-Cassegrains need a 2" diagonal such as the Explore Scientific 2" Diagonal or Celestron 2" Dielectric Star Diagonal. Most Dobsonians with a 2" focuser take it directly.
• A solid focuser: these are large eyepieces (141mm × 58mm), so a 2" focuser with a compression ring holds them best. Rebalance a Dobsonian or refractor after inserting one.
• A nebula filter: a 2" UHC or OIII filter threads onto the barrel for emission nebulae from suburban skies.
• A Barlow: the Tele Vue 2x Big Barlow doubles the magnification, turning this eyepiece into an effective 4.5mm.

Which 92° ED eyepiece is right for you?

Want something smaller and lighter? The 72° ED series uses the same ED glass in a narrower field. See all our eyepieces.

What's in the box

• Explore Scientific 92° ED 9mm eyepiece with dust caps

Diagonals, Barlows and filters are sold separately.

Explore Scientific 92° ED 9mm FAQ

Will it fit my telescope?

It has a 2" barrel, so it needs a 2" focuser or diagonal. It won't fit a 1.25"-only focuser.

What magnification will I get?

Divide your telescope's focal length by 9. In an 8" f/6 Dobsonian (1200mm) that's 133x; in an 80mm f/6 refractor (480mm) it's 53x; in a Celestron 8" SCT (2032mm) it's 226x.

Can I use it with glasses?

Yes. 18mm of eye relief is enough for most people who observe with glasses.

92° or 72°?

The 92° ED shows about 60% more sky at the same magnification and makes objects feel immersive, especially in a Dobsonian. The 72° ED series is smaller, lighter and less expensive, and easier to balance on small telescopes.

Is it really waterproof?

Explore Scientific sells the 92° ED series as waterproof eyepieces, which helps on dewy nights and when cleaning. Dry it before putting the caps back on.

Specifications