Explore Scientific 100° Series 3" 30mm Waterproof Eyepiece

The 100° Series 30mm is the largest eyepiece in the Explore Scientific lineup: a 3" barrel design with a 100° apparent field of view. It is a wide-field instrument that transforms how you see the sky.

The multi-element optical design maintains sharp, well-corrected images across the full 100° field. The 3" barrel accommodates a 52.2mm field stop. Argon-purged waterproof construction keeps the optics sealed against moisture and fog-free inside. Every 100° Series eyepiece is tested submerged in 1 meter of water for 30 minutes, and the dry argon fill also extends the life of the internal coatings.

Key Features

• 3" barrel. The only 3" eyepiece in the Explore Scientific lineup, with a 52.2mm field stop.
• 100° apparent field of view. Hyper-wide panoramic views that create a genuinely immersive experience.
• Multi-element optics. High-quality glass types maintain sharpness and correction across the enormous 100° field. The design uses nine elements, with lenses of low-dispersion, high-refractive-index glass.
• Argon-purged waterproof housing. Sealed against moisture and fog. The sealed, argon-filled body also keeps fine dust and fungus out.
• EMD coatings. Enhanced Multi-Layer Deposition (EMD) coatings on all air-to-glass surfaces, with edge-blackened elements for maximum contrast.
• 19mm eye relief. The longest in the 100° Series. Eye relief is the distance from the eye lens at which you see the whole field.
• Fold-down eyecup. The silicone rubber eyecup folds down for comfortable eye positioning during extended sessions.

Ideal For

• Dedicated wide-field deep-sky observers. For those who want the largest eyepiece in the Explore Scientific lineup.
• Telescopes without tracking. Objects are easier to find in a 100° field, and they stay in view a long time before the telescope needs moving.
• Faint objects. The wide field makes averted vision easy: looking slightly to one side of a faint object puts its light on a more sensitive part of the eye.

Accessories & Compatibility

• Needs a 3" focuser. A 52.2mm field stop is wider than a 2" (50.8mm) barrel, so this eyepiece needs a 3" focuser, and a 3" diagonal for a right-angle view; it does not fit a 2" focuser or diagonal. The Explore Scientific ED152 Carbon Fiber Refractor comes with a two-speed 3" focuser.
• In the ED152. At its 1216mm focal length and f/8, it gives 41x, a 2.5° true field and a 3.8mm exit pupil.
• 3" diagonal. The ED152 ships with a 2" diagonal, which does not take this eyepiece. The Explore Scientific 99% Reflective 3" Diagonal holds a 3" barrel at a right angle, and its included 2" adapter takes 2" eyepieces.
• Balance. At 2,353 g (82.9 oz), it moves a telescope's balance point. Explore Scientific recommends installing the diagonal and any large eyepiece before balancing a refractor in its cradle rings.
• For a 2" focuser. The other 100° Series eyepieces, from 5.5mm to 25mm, have 2" barrels; the longest is the 100° Series 25mm.