Explore Scientific 100° 30mm Waterproof Eyepiece - 3"

The Explore Scientific 100° 30mm Eyepiece: An Overview

You may be startled at the wide expanse of inky black sky the first time you look through a 100° Series eyepiece, and may even forget there is an eyepiece between you and the universe.

It needs a telescope with a 3-inch focuser. As the longest focal length of the series it gives the lowest magnification and widest true field of the 100° Series in a given telescope.

The 100° Apparent Field

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

In a non-driven telescope, it says 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, allowing you to see fainter images.

19mm of Eye Relief for Extended Observation

The 100° 30mm has 19mm of eye relief, the longest in the 100° Series. Eye relief is the fixed distance from the eyepiece's final lens to the point where your eye must be positioned to see the full field of view. A longer eye relief means you do not have to press your eye right up against the lens, reducing eye strain and making the viewing experience more comfortable and natural.

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

A 9-Element System

The 30mm uses 9 lens elements. It has an optimized optical design, exotic glass combinations for optimum results and durable coatings.

All 100° Series eyepieces are fully multi-coated and edge-blackened to produce maximum contrast.

Argon-Purged and Waterproof to 1 Meter

Each 100° Series eyepiece is internally sealed and purged with inert, dry argon gas, with a waterproof, fog-proof housing.

It says the purge also maximizes the life of the internal coatings, and every 100° eyepiece is tested by submerging it to 1 meter of water for 30 minutes.

The 3-Inch Barrel and 2353g Build

Its 52.2mm field stop is wider than a 2-inch barrel, so the 30mm uses a 3-inch barrel. Barrels in the series are tapered for extra security.

This no-compromise optical design results in a substantial piece of equipment. The eyepiece weighs 2353 grams (over 5 pounds) and measures 200mm in length with a maximum width of 107mm. Use a 3-inch focuser that holds it firmly, and expect to rebalance the telescope.

Calculating Your View with a 52.2mm Field Stop

The field stop is the metal ring inside the eyepiece barrel that defines the sharp edge of the circular field of view. Its diameter is the ultimate limit on how much sky you can see. The Explore Scientific 100° 30mm eyepiece features a massive 52.2mm field stop, which is critical to delivering its expansive views.

You can calculate the true field of view (TFoV) this eyepiece will deliver on your specific telescope using a simple formula: TFoV = (Field Stop Diameter / Telescope Focal Length) x 57.3. The result is the actual patch of sky you will see, measured in degrees.

• 2500mm focal length: the calculation would be (52.2 / 2500) x 57.3, resulting in a true field of view of approximately 1.2 degrees.
• 1800mm focal length: (52.2 / 1800) x 57.3 ≈ 1.66 degrees.

Low-Power Performance with a 30mm Focal Length

Magnification is determined by the focal length of your telescope divided by the focal length of your eyepiece. With its 30mm focal length, this eyepiece is designed to provide very low power, which is ideal for wide-field scanning and observing large-scale celestial objects.

To determine the magnification this eyepiece will provide on your telescope, use the formula: Magnification = Telescope Focal Length / 30mm.

• Example 1: On a telescope with a 2500mm focal length, this eyepiece provides 2500 / 30 = 83x magnification.
• Example 2: On an instrument with a 1800mm focal length, it yields 1800 / 30 = 60x magnification.
• Example 3: With a very long focal length 3500mm telescope, it would provide 3500 / 30 = 117x magnification.

System Integration: A 3-Inch Focuser Requirement

The Explore Scientific 100° 30mm is a specialized piece of equipment that requires a telescope with a compatible 3-inch focuser. It will not fit in standard 1.25-inch or 2-inch focusers.

While the Explore Scientific 100° series eyepiece line is designed to work with optional focal extenders for increasing magnification, it is important to note that the Explore Scientific catalog currently lists focal extenders only in 1.25-inch and 2-inch barrel sizes. There is no compatible 3-inch focal extender offered by Explore Scientific for this eyepiece. Therefore, it is intended to be used at its native 30mm focal length.

Handling and Care

At 2353 g (82.9 oz), grip it firmly and secure it in the focuser. The box holds the eyepiece itself.

The sealed housing keeps the inside closed; clean only the outer lenses, and only when needed.