How will the ES 9mm 100° eyepiece perform on Jupiter with an 8" Dobsonian?
In a typical 8" f/6 Dobsonian (1200mm focal length), the 9mm eyepiece yields 133x magnification. This is an excellent power for viewing Jupiter's main cloud belts, the Great Red Spot, and the Galilean moons. The 100° field means you can watch the planet drift for a long time before needing to nudge the telescope, making for a very comfortable and immersive observing session.
Is the 9mm focal length good for viewing the Ring Nebula (M57) in a 10" f/5 scope?
Yes, it's a great choice. In a 10" f/5 Newtonian (1270mm focal length), the 9mm eyepiece provides 141x magnification. This is high enough to clearly resolve the "donut" shape of the Ring Nebula (M57) and potentially glimpse the faint central star. The wide 100° field will frame the nebula beautifully against a dark, expansive background.
What is the main benefit of the 100° field of view on the ES 9mm eyepiece?
The primary benefit is the immersive, "spacewalk" feeling it creates. It also makes finding and tracking objects much easier, especially with non-motorized telescopes like Dobsonians. Objects stay in the field of view for a significantly longer time compared to standard eyepieces, allowing you to relax and study details without constant adjustments.
Why is an argon-purged, waterproof eyepiece like the ES 9mm 100° useful?
An argon-purged and sealed eyepiece is protected from the environment. Key benefits include:
-
No Internal Fogging: It will not fog up internally during nights with heavy dew.
-
Contaminant-Free: Dust, moisture, and fungus cannot get inside the eyepiece.
-
Longevity: The internal lens coatings are protected, ensuring a longer lifespan for the eyepiece.
Do I need a 2" focuser to use the Explore Scientific 9mm 100° eyepiece?
Yes. This eyepiece has a 2-inch barrel and requires a telescope with a 2-inch focuser. It cannot be used with telescopes that only accept 1.25-inch eyepieces.
Will I need a coma corrector with this 9mm eyepiece in my fast Newtonian?
In fast telescopes (f/5 or lower), hyper-wide eyepieces like the ES 100° 9mm will show coma, an aberration that makes stars near the edge of the field appear comet-shaped. While still usable, pairing it with a good coma corrector like the Tele Vue Paracorr Type 2 will provide much sharper stars across the entire 100° field of view.
