I've seen a monocentric, which is a cemented triplet design. I've never used one in a telescope, though, and I was told that this variety had a pretty obvious ghost image and very little eye relief. Your biggest problem with these eyepieces is finding them. I think this one was made by Intes, but Intes is not known for excellence in eyepiece manufacturing. I don't think eye relief is theoretically all that bad compared to Abbes and Plossls, so perhaps in medium and longer focal lengths it is tolerable.
The Tolles is a single, thick lens design and so is limited in its correction ability the way any single lens must be.
--
Mike
The Tolles is a single, thick lens design and so is limited in its correction ability the way any single lens must be.
--
Mike
