Evolution of eyepiece designs

[Wavytone]

Found this recently on cloudynights and I can't help feeling it warrants a sticky for the un-initiated:

http://www.brayebrookobservatory.org...fEYEPIECES.pdf

http://www.brayebrookobservatory.org...S/treediag.jpg

http://www.brayebrookobservatory.org...arlow%20Lenses

It's interesting to note the Plossl dates from the 1860's and the orthoscopic design dates from 1880... considering what the prices of these were 30, 40 years ago the current prices for some of these 4-element designs seem a bit steep these days.

[Scoper (Malcolm)]

The Brayebrooke Observatory website is well worth a browse. Lots of info and some good historical and technical stuff on eyepieces.
Chris Lord seems to share your opinion on the price of 4 element eyepieces Wavytone; Here is a link to a pdf file comparing Brandon, Televue and GSO plossls:

http://www.brayebrookobservatory.org...%20Brandon.pdf