Explore Scientific 92° ED Series 9mm Waterproof Eyepiece

The 92° Apparent Field in a 9mm Focal Length

The 9mm is ideal for planetary detail and smaller deep sky objects while keeping a sense of space and scale. You may be startled at the wide expanse of inky black sky the first time you look through a 92° Series eyepiece, and may even forget there is an eyepiece between you and the universe.

The 92° field lets objects stay in view longer and reduces the need for constant repositioning, which is especially valuable at higher magnifications.

Comfortable High-Power Viewing with 18mm of Eye Relief

The 9mm has 18mm of eye relief. The 92° ED Series offers long eye relief, serving up great views with reduced eyestrain, and comfort during extended viewing.

How much of the field an eyeglass wearer sees depends on the glasses; Explore Scientific does not state it.

9-Element Design with ED Glass

The 9mm uses 9 elements in 6 groups, including extra-low dispersion (ED) glass. ED glass offers reduced color fringing, sharper high-contrast views and better performance at high magnification.

It explains that ED glass has a high Abbe number, so it spreads white light into colors less, keeping colors focused together; the colors you see, like subtle differences in star color or planetary tones, are closer to reality.

• ED Glass: Reduces color fringing for sharper, high-contrast views and truer color rendition, especially at high power.
• Fully Multi-Coated: The optics are fully multi-coated, with durable coatings.
• Edge-Blackened Optics: Lens edges are blackened for maximum contrast.

Argon-Purged Waterproofing and a 2-Inch Tapered Barrel

Each eyepiece is O-ring sealed and purged with an inert gas to create a waterproof environment, with a waterproof, fog-proof housing.

The barrel is tapered for extra security. The eyepiece measures 141mm long and 58mm wide; the catalog gives no weight.

Calculating Magnification and True Field of View with the 9mm Eyepiece

The 9mm focal length of this eyepiece is ideal for high-power observation. To calculate the magnification it will provide with your telescope, simply divide your telescope's focal length by 9mm. For example, a telescope with a 1200mm focal length will achieve 133x magnification (1200mm / 9mm).

While the 92° apparent field describes the immersive experience, the true field of view (TFoV) describes how much actual sky you will see. The TFoV is determined by the eyepiece's 13.5mm field stop. True field ≈ 13.5 / telescope focal length × 57.3 degrees: about 1.3° at 600mm, 0.64° at 1200mm and 0.39° at 2000mm.

Expanding Magnification with Explore Scientific 2-Inch Focal Extenders

For even higher power when atmospheric conditions permit, the 9mm eyepiece is compatible with Explore Scientific's 2-inch Focal Extenders. Optional focal extenders are available for the series, and a focal extender increases the magnification of any eyepiece with the same barrel size.

In Explore Scientific's words, 3 eyepieces offer 6 magnification choices with a focal extender.

• FE02-020 2x Focal Extender: Doubles the magnification of the 9mm eyepiece, effectively turning it into a 4.5mm eyepiece.
• FE03-020 3x Focal Extender: Triples the magnification, giving the magnification of a 3mm eyepiece.