What does "Argon-purged" mean for the Explore Scientific 68° 20mm eyepiece?
Argon-purging means the air inside the eyepiece has been replaced with dry, inert argon gas and then sealed. This makes the Explore Scientific 68° 20mm eyepiece completely waterproof and prevents internal fogging, dust intrusion, and the growth of fungus on the lenses. It ensures the eyepiece performs reliably in any weather condition and lasts a lifetime.
How does the Explore Scientific 68° 20mm perform on the Orion Nebula (M42) in an 8" f/10 SCT?
In a typical 8" f/10 SCT (2032mm focal length), the ES 68° 20mm eyepiece provides 102x magnification. This is an excellent power for framing the entire Orion Nebula (M42), from the bright Trapezium star cluster at its core to the faint, sweeping outer arms. The 68° field will feel immersive and provide a dark sky background to enhance nebulosity.
Is the 20mm focal length good for planetary viewing with the ES 68° eyepiece?
The 20mm focal length provides medium power, which is great for locating planets and viewing them in context with their moons, such as Jupiter and the Galilean satellites. For detailed observation of planetary features like Jupiter's Great Red Spot or Saturn's Cassini Division, you would typically use a much shorter focal length eyepiece (e.g., 6mm to 9mm) or a Barlow lens with the 20mm eyepiece.
What is the benefit of a "parfocal" eyepiece like the ES 68° 20mm?
A parfocal eyepiece requires little to no refocusing when swapped with other eyepieces in the same series. The main benefit is speed and convenience. When you switch from the 20mm to another ES 68° eyepiece, your target will snap back into focus almost instantly, saving you from having to hunt for focus in the dark.
Will I need to wear my glasses with the Explore Scientific 68° 20mm eyepiece?
The Explore Scientific 68° 20mm features long eye relief, which allows you to hold your eye at a comfortable distance from the lens and still see the entire field of view. This design is ideal for observers who wear glasses to correct for astigmatism. For those who don't, the included foldable rubber eyecup helps maintain the correct eye position.
Is the Explore Scientific 68° 20mm eyepiece a good all-around choice?
Yes, for many telescopes, a 20mm focal length is an excellent workhorse for deep-sky observing. It provides enough magnification to resolve details in many galaxies and nebulae while still offering a wide enough true field of view to easily locate objects. It's a versatile choice that bridges the gap between low-power scanning and high-power planetary viewing.
