Right Lee thanks. Just in case it mattered, I have got used initially to checking this both ways, and apart from the odd Bushnell
, for me, with updated glasses they have seemed to be ok at zero.
I have reckoned that my glasses (meaning 'spectacles') have put me to zero and that has solved the problem. The glasses have themselves been a nuisance, simply because "eye relief" is often quoted so imprecisely. Anyway crude testing has indicated that using my glasses has helped a lot, presumably because of astigmatism so that, at least for me, this is the way to go.
Unfortunately, although my lovely recently acquired vintage 8x30 WA Avocets have roll-down eye cups it is not nearly enough. They are already plenty sharp without it so it would be nice to see what they would be be like with correction for that particular type of refractive error. To me it has been interesting both to see how much the Avocets need good light to perform, and that otherwise their (early?) coatings seem to be able to handle things very well. Perhaps they were especially good even then, or perhaps sharpness and CA were not so much of a problem before the 'roof prism' takeover.
From various comments it has seemed to me that, since then, it has been light transmission as well as control of CA (apparently not so critical with porros) which may have become more important, even than sharpness.
Clearly porros can still rule, SE 8x32, and i.m.o. even still be good at very reasonable cost with Celestron 7x35, but I just don't like the idea of the eyepieces wobbling around on a stalk, or the stiff focus action which seems to be required to waterproof the latter.
With porros I have often tried moving them individually by hand and found that it made no difference, while images of broken bridges have certainly made an impression. May I ask what else might Not be Happening (to change focus) when each eyepiece is moved individually by hand? Is it just that the eyes accomodate to match the altered binocular relationship?
I guess that 'waterproof' is largely a marketting/subjective thing: how often do I go out at all? (rhetorical)....let alone how often do many others wander about in the rain? Anyway the focussing action of waterproof porros seems (in my limited experience) to introduce unacceptable friction and stiffness.
If the eyepieces were to be outside the volume which has been 'nitrogen purged' (roofs?) while something (?) else is moved, this would not be a problem. However I have somewhere seen reference to pumping action when porro eyepieces are moved, so how is this accommodated please? Is it just a question of greased O rings on the eyepiece tubes? ...surely not, or maybe that's why porros are not the thing i.e. because they can't really be made waterproof?
