Explore Scientific 72° ED Series 30mm Waterproof Eyepiece (2")

Ultra-wide, low-power views with 25mm of eye relief

The Explore Scientific 72° ED Series 30mm Waterproof Eyepiece is a 2-inch eyepiece for ultra-wide, low-magnification views. It has a 72° apparent field, a 2" barrel, 25mm of eye relief and a 37.3mm field stop, and its optics include H-FK61 ED glass to keep color fringing low and contrast high. Explore Scientific builds the series to be waterproof, and this eyepiece weighs 600g (21.2oz).

Key specs: 30mm focal length · 72° apparent field · 2" barrel · 25mm eye relief · 37.3mm field stop · 6 elements in 4 groups · H-FK61 ED glass · waterproof · 600g (21.2oz)

What you'll see

• The Pleiades filling the view in an 8-inch Dobsonian.
• The Veil Nebula and North America Nebula with a UHC or OIII filter.
• The Andromeda Galaxy with its companions, and rich Milky Way star fields in Cygnus and Sagittarius.

In an 8" Dobsonian (1200mm) the 30mm gives 40x and a 1.78° true field. In an 80mm f/6 refractor (480mm) it gives 16x and a 4.45° field. For comparison, the full Moon is about 0.5° across.

Why the 72° ED series

• Wide without the bulk: 72° is wide enough to frame objects with plenty of sky around them, while keeping the eyepiece smaller and lighter than 82° and 100° designs.
• 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.
• 25mm eye relief: comfortable for most eyeglass wearers.
• 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 nebula filter: a 2" UHC or OIII filter threads onto the barrel and makes the Veil and North America Nebulae stand out from suburban skies.
• A Barlow: the Tele Vue 2x Big Barlow doubles the magnification and turns this eyepiece into an effective 15mm.
• More of the series: pair it with the 40mm and 25mm for a matched set with the same 72° field and feel.

Which 72° ED eyepiece is right for you?

See all our eyepieces.

What's in the box

• Explore Scientific 72° ED 30mm eyepiece with dust caps

Diagonals, Barlows and filters are sold separately.

Explore Scientific 72° ED 30mm 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 30. In an 8" f/6 Dobsonian (1200mm) that's 40x; in an 80mm f/6 refractor (480mm) it's 16x; in a Celestron 8" SCT (2032mm) it's 68x.

Can I use it with glasses?

Yes. 25mm of eye relief is enough for most people who observe with glasses.

30mm, 25mm or 40mm?

The 25mm gives more magnification (48x in an 8" Dob) for smaller, brighter targets. The 40mm gives a wider, brighter view (30x, 2.31°). The 30mm sits between them at 40x.

Is it really waterproof?

Explore Scientific sells the 72° ED series as waterproof eyepieces, which helps on dewy nights and when cleaning. Dry it before putting the caps back on.

Specifications