the famous "Bargain Basement Optics" eyepiece.
The Erfle design uses a positive lens as an eyelens and two achromats for the central and field lens. The design gives an extraordinarily wide apparant field of view because each element widens the field of view of the one before it. Some Erfles use a single positive lens between two achromats, and others use three achromats. The smaller lens is shown for scale. The eyepiece caps were turned from white abs plastic. Please note that I build only for my own instruction and none of these eyepieces are for sale.
As an experiment, I decided to build an eyepiece out of the worst optics that I could find rattling around my desk drawer.
These lenses had small chips on the edges as well as the center, bad coatings, and lots and lots of small scratches. In a moment of desperate humor, I named it the "Bargain Basement Optics" brand and left my own name off. At star parties I bring it out and let people try it without explaining its origin. Luckily, they cannot see the name in the dark. It never fails to get good reviews. It's amazing how little a scratch or chip will effect an image.