UO HD Ortho evolution?

I was testing a recent modification to my Baader Herschel Wedge to allow me to use Denkmeier Binoviewers. I spent a good deal of time testing out a number of different eyepiece pairs to determine which gave the most impressive views. While using pair of 7mm UO Ortho HDs I focused on Sol's limb and then panned over to AR2251 and tweaked focus. In the middle of the field of view was a large bright, circular spot. Close inspection revealed it to be a reflection from one of the two HD Orthos. These eyepieces were acquired from the used market in separate transactions from different sellers, and I am almost certain they are first generation HDs.

When I acquired the second 7mm HD I immediately noticed subtle differences. One of them was marked Japan, and the other not marked with the Country of Origin. The "unmarked" one came with a shorter barrel lacking an undercut which is now a "feature" of second generation HD Orthos. This UO HD Ortho has been in circulation awhile which makes me think it is a first generation. The previous owner may have swapped barrels with another eyepiece or maybe UO used smooth barrels on some early HDs. (For parfocal use in the Binoviewer I swapped it with a 6mm HD so they matched.) The retaining rings securing the lens elements are of a different diameter.

To confirm my suspicions I removed both HD Orthos and inserted my 19mm Pans. I verified the absence of the bright spot. It was gone. I then re-inserted the 7mm Orthos one at a time in the right SCD of the Binoviewer. The unmarked Ortho with the large retaining ring showed no spot. Moving on to the one marked "Japan" with the smaller retainer, there it was again - a bright circular spot in the center of the FOV! Close inspection reveals it to be a specular reflection off the thread locker on the smaller diameter optical retaining ring.

Now the question is: Why are they so very different mechanical designs? Was this a design change due to similar experiences from other users? I suppose I'll have to reach out to UO to see if they can explain....Does anyone here have one of these 7mm HDs that you can compare and comment on?


Regards,
Gary

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Generally these kind of eyepieces were made in large quantities by various subcontractors in Japan, Taiwan and China. When one subcontractor goes out of business, another takes his place, so then there will be variations in the optics and mechanics.

Even today generic Orthos, Plossls etc are marketed under a number of different trade names. The mechanical and optical designs are nothing special and in some cases depended on the parts that the specific subcontractor had in stock. It is easy enough, if you are an OEM, to order generic eyepieces and put your brand on them. They are available now by the millions if desired, from large optical corporations in China.