I haven't tried it with a large scope(mine is a 6" f/5 reflector), but love low power binoviewing of bright DSOs. I use a 2x OCA with my 25mm HD Orthos producing 61x. BTW, you lose brightness but not resolving power with a binoviewer.
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BTW, I am also considering the HD ortho 18mm as it appears to not have much of a recess of the lens. Another thing to consider is that the eyepiece that had the shortest eye relief with my glasses on was the 12mm Dual ED which has a stated 13mm eye relief.
Curious if anyone has had the opportunity to test the 18mm Tak abbe ortho with glasses on. The eyepiece isn't common where I live so I can't test before purchasing it. I wear glasses for astigmatism and also generally observe with a binoviewer. thanks in advance