Rich, take a look at this site; http://www.siebertoptics.com/ I'm not sure what type of lens' he uses that gives such a large eye lens but the FOV seems bigger, the eye relief seems to me to be a little better, but I haven't done any type of measuring to be able to tell you exactly how much more than versus a standard ortho or plossl of the same focal length. I'm sure that a call or email to him would answer some questions, as he's a very friendly guy! Howard PS, Chuck I'd cough up $15 bucks for a kit!! --- Richard Tenney <retenney@yahoo.com> wrote:
Chuck,
The kits sound like a terrific deal. BTW, I start a new job on Tuesday! Yahoo!
One question I've had for a long time, and I'll likely show my ignorance of optics here. But I've been wondering why it is that when you get down to the high power 3 or 4 element eyepieces (e.g., orthos and ploessls) the diameter of the glass shrinks to a tiny hole and the eye relief shrinks down to the point where you almost have to put your eyeball right to the glass to see anything? Does the short focal length not allow for a bigger diameter with the same curvature of the glass required for the magnification? In other words, is it possible to make a 6mm ortho that fits in a 2-inch barrel that doesn't require the top lens element diameter to be smaller than a soda straw? I suspect the answer is probably too long and complex for posting on this list, but if there's a short answer, I'd like to hear it! At least I hope you will address questions like this, and what the remedies might be if any (aside from adding more optical elements, creating in effect a built-in barlow which is what I suspect the radian and nagler designs employ, right?).
One of the things that Mr. Dobson said about binocular eyepieces were the superb eye relief most of them afforded.
Anyway, sounds like you might need to start the seminar with a short course on optical physics! I for one sure wouldn't mind.
Meanwhile, I'll have to go back and look up your S&T article. I never did read it that I can remember.
Sorry to be so long winded. And please don't feel like you have to respond to all this rambling (a waste of your time). You can save it for your seminar this summer.
-Rich
--- Chuck Hards <chuckhards@yahoo.com> wrote:
I'll start seeing what optics are available, and gathering materials. To keep costs down, we'll probably build a Plossl or true symmetrical. If I can find some inexpensive triplets, the ortho can be explored. I may be able to offer kits of both designs, wait and see.
These "kits" will cost me about $15 each; is everyone who wants to participate able to pony-up fifteen bucks? I will make no profit on this endeavor,
but
must cover costs.
Although we probably will NOT use wood for a housing, optically we will be building something similar to the "Homemade eyepieces" I described in S&T a couple of years ago (Feb. 00).
Let me know if there are any particular questions you would like the speaker(s) to address.
Thanks!
C.
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