So a while back I decided to make my own "Monocentric" eyepiece using commercial parts to see what all the hubbub was about.
The TMB "Monocentrics", both the old ones and the new "Super Monocentrics" sold by APM are pretty pricey at $500 per eyepiece. In addition, the used Zeiss "Monocentrics", command prices of $1000. So I was anxious to see what the deal was.
You may be wondering at this point why I keep putting "Monocentric" in quotes. That would be because none of the TMBs, old or new, or the Zeiss is a "Monocentric" eyepiece. At their heart is a Hastings triplet. Hasting's triplets are used in high end magnifiers because they have probably the best optical properties of a triplet, save for a true Monocentric. Monocentric means "one center", and on the true Monocentric design all of the elements have a common center. A Hasting's triplet does not.
So if you want to put one together to see what kind of performance you will get, before plunking down your hard earned cash for a TMB or Zeiss:
Here's the $40 c-mount adapter for the lens:
Here's the $95 Hastings triplet lens:
And here's the $36 1 inch to 1 1/4 inch adapter:
Put the lens in the c-mount and secure, then screw the c-mount on to the adapter. Viola, you have you're very own 10 mm. "Monocentric" eyepiece.
Some comments on it. It has a MagF coating on it and reduces or eliminates "pincushion distortion", spherical and chromatic aberrations.
What I've seen in use is that it is very sharp in the center but has significant field curvature, thus it gets blurry near the edge of a very small 30 degree field of view. Planetary and star colors are nicely saturated. But in the end, my BGOs and Brandons are just as good. So I'll let others decide of the commercially and, in the case of the Zeiss, used "Monocentrics" are worth the price. For me they are not.
Clear skies and Have Fun,
Edited by RodgerHouTex, 10 September 2014 - 08:15 PM.