Explore Scientific 100° 20mm Waterproof Eyepiece - 2"

The 100° Apparent Field: A Panoramic Viewing Experience

The huge 100° field gives a panoramic visual experience and relaxes the eye, so you can pay attention to subtle details for extended periods.

It adds that objects are easier to locate, and in a non-driven telescope an object stays in the field a very long time before any adjustment is needed. Hyper-wide eyepieces also make averted vision easy: looking slightly to the side of a faint object puts the image on a part of your eye that is more sensitive to light.

9-Element Optical Design

The optical system of the 20mm eyepiece consists of 9 distinct lens elements. It has an optimized optical design and exotic glass combinations, and all 100° Series eyepieces are fully multi-coated and edge-blackened to produce maximum contrast.

All-Weather Reliability: Waterproof to 1 Meter for 30 Minutes

Each 100° Series eyepiece is internally sealed and purged with inert, dry argon gas, which also maximizes the life of the internal coatings, with a waterproof, fog-proof housing.

Every 100° eyepiece is tested by submerging it to 1 meter of water for 30 minutes.

The 2-inch Barrel: Fit, Security, and a 916 g Build

The Explore Scientific 100° 20mm eyepiece uses a 2-inch barrel; the barrel is tapered for extra security. It weighs 916 g.

With a length of 156mm and a maximum width of 70mm, this is a substantial ocular. When using it, you should ensure your focuser can handle the weight and that your telescope mount is properly balanced.

14.5mm Eye Relief: Comfort and Viewing Technique

This eyepiece features an eye relief of 14.5mm, which is the distance from the top lens to the point where your eye must be positioned to see the full field of view.

Explore Scientific does not say how much of the field eyeglass wearers see.

Calculating True Field from the 34.8mm Field Stop

The true field of view, how much actual sky the eyepiece shows, is determined by its 34.8mm field stop diameter and your telescope's focal length. The field stop is the physical metal ring inside the eyepiece barrel that defines the edge of the view.

You can estimate the true field of view (TFoV) in degrees using the following formula: TFoV ≈ (Field Stop Diameter / Telescope Focal Length) x 57.3. For example, in a telescope with a 1500mm focal length, this 20mm eyepiece would yield a true field of approximately 1.33 degrees (about 1.66° at 1200mm and 1.0° at 2000mm).

20mm Focal Length: Magnification

The magnification is calculated by dividing your telescope's focal length by the eyepiece's focal length (20mm). For instance, 1200mm gives 60x and 2000mm gives 100x.

Optional focal extenders are available for the 100° Series. The 2" FE02-020 (2x) gives the magnification of a 10mm eyepiece and the FE03-020 (3x) that of a 6.7mm.