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Hi Morton. I just arrived home after 4 nights observing where I was comparing a number of new eyepieces, mainly looking for best lunar and planetary performance in my bino viewer. I also spent some time comparing them to my Delos on faint planetary nebula and galaxy clusters at the limit of visibility to see if I could observe a difference.
All the minimum glass type eyepieces were between 15 mm and 18 mm so I had to use a Powermate, which has even more elements than a Barlow. The coatings are so good that any reduction in transmission wouldn't be visually detectable.
I found the minimum glass types with the Powermate performed equally as well as the Delos. I know Alvin Huey in the US uses a TV Barlow with his Zeiss Abbe Orthos in very big Dobs to hunt really faint galaxies. So that's good enough for me.
Bare in mind an Abbe Ortho has a FOV around 44 degrees. You would need to go to a Plossl to get your 50 degrees, but they have even less eye relief than Abbe's. Based on what I have seen over the last few nights I prefer the new Takahashi Abbe Ortho more than the TeleVue Plossl. The 18 mm Tak Abbe has all the qualities you are looking for and 15 mm eye relief makes it very easy to use.
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