Explore Scientific 72° ED Series 20mm Waterproof Eyepiece

The 72° ED Glass Advantage: Chromatic Aberration Control

This eyepiece's optical design centers on Extra-Low Dispersion (ED) glass to minimize chromatic aberration—the false color fringing seen on bright objects like stars and planetary limbs. By correcting for this distortion, the 20mm ED eyepiece produces sharper, higher-contrast images with more natural color rendition across its entire 72° apparent field.

• High-Contrast Views: Suppressing false color results in a darker sky background and makes faint details in nebulae and galaxies easier to discern.
• Edge-to-Edge Sharpness: The ED element helps maintain tight, point-like stars even at the edge of the wide 72° field, creating a more cohesive and immersive viewing experience.

All-Weather Scanning: A Waterproof 20mm Eyepiece

Engineered for reliability in the field, the 72° ED 20mm eyepiece is fully waterproof and gas-purged. This prevents internal fogging during nights with heavy dew and protects the internal lens coatings from moisture and fungus, ensuring long-term durability.

This robust construction, combined with a comfortable eye relief, makes it a workhorse eyepiece for extended observing sessions. Its primary role as a 20mm low-power eyepiece makes it perfect for locating objects and scanning the Milky Way, where changing temperatures and dew are common challenges.

72° ED vs. 50° Plössl: A Wider Context for Deep Sky Objects

A standard 20mm Plössl eyepiece typically offers a 50-52° apparent field of view. While effective, this narrower field can feel restrictive when viewing large-scale structures. The Explore Scientific 72° ED 20mm eyepiece provides a dramatically larger window on the sky.

• Framing Large Targets: The 72° field allows you to frame entire objects like the Pleiades (M45) or the Andromeda Galaxy (M31) within a single view, which is often impossible with a standard Plössl at the same magnification.
• Immersive Experience: The wider field of view enhances the sense of "space-walking," making deep-sky observing more engaging by revealing the surrounding star fields that give context to the main object.