Hi Seth, I heard your joyous exclamations throughout the evening at Capitol Reef, but I don't believe you ever made it to my scope. You do know you've asked a variant of the most dangerous question in astronomy---what should I buy? First, here are a couple of good online review sites: http://www.cloudynights.com/ http://www.scopereviews.com/ Second, you should determine what it is you want to see -- widefield deepsky, lunar, planetary nebula, planets, etc. There's a different ideal eyepiece for each application. Lowell's Pentax is indeed a great eyepiece. You'll notice if you go onto any online sales site that there are many different types of Pentaxes--each with a different (ahem) focus. You'll also find Televue Naglers which are equivalent in quality. But if you're looking for strong detail on the lunar surface, you'll find that many people will recommend something with less glass -- a simple plossl or even an orthoscopic. Third, the C11 is a pretty forgiving scope in terms of eyepieces. Its F/10 focal ratio means that you can use a pretty long focal length eyepiece. WARNING: SIMPLE MATH. Take the focal length of the eyepiece and divide by the focal ratio of the scope. That will give you the exit pupil--that's essentially the size of the image. If the exit pupil is larger than your own pupil, you're just wasting light. A "mature" person may have a maximum dilation of 6 or perhaps 7 mm under very dark skies. So a 35mm eyepiece with an F/10 scope will give you a 3.5mm exit pupil. Nominally that sounds OK. But with a Schmidt-Cassegrain scope, you may begin to see the central obstruction (which is manifested as a difficult-to-hold image) at less than the maximum exit pupil. I experienced a little of this looking through Lowell's scope. Guess I just need new eyes. On the other hand, if you throw a 7mm eyepiece in a C11, you're almost never going to have a night that gives you a decent view at such high magnification. Fourth, you've got plenty of time. Make a nuisance of yourself at SLAS star parties. Try out different eyepieces, though your scope or a similar scope. See what you like. It's a real pity to load up on expensive eyepieces and then find out you only use one or two of them. Finally, I will throw in my 2-cents' worth. A good widefield eyepiece in the 20-21 mm range will give you excellent views and will work in just about any scope. Another good range will be the 13-14 mm range. Once you get under 10mm or so, you enter the high-power world and will have to do some serious investigating of your needs and preferences. Once you get up past 30mm, you really need to try the eyepiece in your scope. Michael -----Original Message-----

From: Seth Jarvis <SJarvis@slco.org> Sent: Aug 29, 2006 12:52 PM To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: [Utah-astronomy] Eyepiece recommendations?

Last weekend's star party at Capitol Reef was fantastic. Many heartfelt thanks to the SLASers who got it organized and for extending the invitation to join the event.

Susie and I took our C11 to the star party and we were amazed by what that ultra-dark sky did for the telescope's views. I'm so used to doing star parties under so-so seeing conditions along the Wasatch Front that I'd forgotten what can be accomplished under a truly dark sky.

I played around with the few relatively inexpensive eyepieces I own and found that by far the best views of the evening were achieved with a 1.25" 30mm Ultrascopic.

Looking through Lowell's 10" Meade with his amazing Pentax eyepiece got me to thinking that perhaps I need to look into optimizing my C11's performance by getting better quality eyepieces. My problem is that there are a zillion eyepiece choices and I don't know what types of eyepieces are best-suited for a C11 and the sort of general-public viewing that dominates my use of that telescope.

Anyone care to offer wisdom and/or opinions on the subject? (Any chance I can do this without going broke?)

Thanks,

Seth Jarvis

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