You're exactly right. The higher the refractive index, the greater the angle of dispersion. Now, here's the catch: The traditional eyepiece designs, like Plossls, Erfles, orthos, Kellners, etc., were all designed using "regular" glass of medium dispersions. Those are the designs we'll address at the eypiece seminar. New designs, such as the Nagler, utilize high-index glass in their designs. Once you enter this territory, "second-order" and higher math takes over, and frankly some of it is beyond me. A whole new world of refractive behavior takes over once you get into high-index glass. C. --- Jim Gibson <xajax99@yahoo.com> wrote:

Chuck

I, like many others, am very interested in you eyepiece seminar. I have been doing some reading about eyepieces and I came across this interesting technical term. The hype I read said that the eyepiece was made of “high-index glass”. I have heard that term before in reference to a fly rod I bought. The hype said that they used “high-index graphite”. So I am curious if I can carry my fly-fishing knowledge over into astronomy. Let me take a SWAG at it. SWAG - that stands for Scientific Wild Ass-tronomical Guess.

When a fly rod casts a fly line or unloads, in a high-index graphite rod the tip quickly dampens so as not to induce a sinusoidal wave into the fly line. OK here’s the SWAG. High-index glass will bend the light more quickly thereby requiring less glass.

Am I in the ball park or should I just stick to fly fishing?

Jim

--------------------------------- Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now

__________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com