What is the main advantage of the Explore Scientific 82° 8.5mm eyepiece for eyeglass wearers?
The primary advantage is its 15mm of long eye relief (LER). Long relief is a must for eyeglass wearers because it allows them to enjoy the full field of view.
How does the 82° field change planetary observing?
In a 2000mm focal length telescope the 8.5mm gives about 235x. The planet's size is the same as in any 8.5mm eyepiece, but the 82° field shows much more sky around it. That gives the planet longer to drift across the field before you nudge a manual mount.
Is the Explore Scientific 8.5mm LER eyepiece good for resolving the Trapezium in the Orion Nebula (M42)?
Yes. At high power the four main Trapezium stars are easy, and the bright nebulosity around them shows structure.
What does "Argon-Purged Waterproof" mean for the ES 82° 8.5mm eyepiece in practice?
The eyepiece is gas-purged and O-ring sealed:
- It will not fog up internally when moving from a warm house to a cold observing site.
- Contaminants are kept out of the housing.
- The sealed design simplifies cleaning the exterior lens surfaces.
Will I need an Explore Scientific Focal Extender with this 8.5mm eyepiece?
It depends on your telescope and atmospheric conditions. The 8.5mm eyepiece already provides high magnification on its own. In long focal length telescopes it is already high power; a 2x Focal Extender (FE02-125) suits short focal length telescopes or very steady nights. Explore Scientific's extenders keep the eyepiece's apparent field and eye relief.
How does the 280g weight of the ES 8.5mm LER eyepiece affect balancing a telescope?
At 280 g it is heavier than a small Plössl, so on a small, finely balanced telescope you may need to rebalance when switching eyepieces.
How large is the 8.5mm LER?
Size is 106mm long by 50mm wide, and it weighs 280 g, with a 1.25" barrel and 7 elements in 5 groups.
What magnification does the 8.5mm give?
Divide the telescope focal length by 8.5: about 47x at 400mm, 71x at 600mm, 141x at 1200mm and 235x at 2000mm.
