Wednesday, June 04, 2014

Just A Little Note About Eyepieces

There's no substituting good eyepieces.
Aside from being a somewhat awkwardly phrased sentence, it is an utter truth. At a minimum, you need three eyepieces for any telescope. Years of practice, experience, and standing on the shoulders of giants has taught me that.
Traditionally, and for a very long time, most telescopes came with Huygenian eyepieces. These simple, two element eyepieces are just okay, and not much better. Their biggest problem is eye relief, making viewing through them a less than desirable experience. I use them, to be honest, but I don't really recommend them. The lowest quality eyepiece I recommend is a Kellner. Think of this as an evolved Huygenian eyepiece with better eye relief and a much better field of view. Next up the ladder, and still very affordable, are Plossls. From there, you start to climb somewhat in expense and complexity, almost always corresponding with better viewing.
Yet I still use cheap eyepieces and accessories. Why?
I don't know, perhaps I'm lazy.
Here I am, in Charlotte Hall, Maryland, and the one eyepiece I choose to bring is a 9mm Kellner. This isn't so bad, but I've chosen to couple it with an inexpensive 2x Barlow, one that appears to be a single element, a lone plano-concave lens.
And it is not quite okay.
For stellar work, it seems to be okay, though just slightly. However, for planetary work (and right now, the evening sky is blessed with three planets to choose from), it fails miserably, at least in combination with my old Monolux 60mm F7.5 "Bianca".
The lesson here?
I have a much better Orion 2x Barlow. Use it.
Live and learn.
After all, there is no substituting good eyepieces.

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