What makes the Explore Scientific 82° 30mm eyepiece "waterproof" and "argon-purged"?
Each eyepiece is O-ring sealed and purged with an inert gas to create a waterproof environment, giving a fog-proof housing.
How wide a true field does the 30mm give?
With its 43mm field stop the true field is about 3.1° at 800mm focal length, 2.05° at 1200mm and 1.23° at 2000mm.
How does the 82° field of the ES 30mm eyepiece help with observing faint objects?
The 82° field relaxes your eye so you can observe longer, and makes averted vision easy: looking slightly to the side puts the image on a more light-sensitive part of your eye, allowing you to see fainter images.
Can I use the 30mm with a Focal Extender?
Yes. The Explore Scientific Focal Extenders suit this series; the 2" models are the FE02-020 (2x) and FE03-020 (3x). The 2x gives the magnification of a 15mm eyepiece, doubling the magnification while maintaining the comfortable 21.6mm eye relief and wide 82° apparent field of the original eyepiece.
What view does the 30mm give at 2800mm focal length?
At 2800mm focal length it gives 93x and a true field of about 0.88°.
How much does the Explore Scientific 82° 30mm eyepiece weigh and will I need to rebalance my telescope?
The eyepiece weighs 1007 grams (2.2 lbs). Expect to rebalance when switching between it and lighter 1.25" eyepieces.
With 21.6mm of eye relief, is the ES 82° 30mm eyepiece suitable for observers who wear glasses?
It has 21.6mm of eye relief. Long relief is a must for eyeglass wearers because it allows them to enjoy the full field of view.
How do I calculate the true field of view for my telescope with the ES 82° 30mm eyepiece?
The true field of view depends on the eyepiece's 43mm field stop and your telescope's focal length. You can estimate it with the formula: TFOV ≈ (43mm / Telescope Focal Length in mm) * 57.3. For a telescope with a 2000mm focal length, the true field would be approximately 1.23 degrees.
What is the benefit of the 43mm field stop on the Explore Scientific 82° 30mm eyepiece?
The 43mm field stop is the physical aperture inside the eyepiece that defines the edge of the field of view. Its large size is what enables the eyepiece to deliver an extremely wide true field of view on the sky, allowing you to frame massive deep-sky objects in a single view.
What magnification does the 30mm give at 1200mm focal length?
Using the formula (Telescope Focal Length / Eyepiece Focal Length), the magnification would be 1200mm / 30mm = 40x.
How does the optical design of the Explore Scientific 82° 30mm contribute to image quality?
The eyepiece uses a 7-element, 4-group design with low-dispersion glass and Enhanced Multilayer Deposition (EMD) coatings. It is optimized for high contrast, high resolution and flat field characteristics, with blackened lens edges and flat black internal surfaces to keep internal reflections to a minimum.
