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eye relief for 18mm orthos?

Started by jwilson, 07/13/2010 06:11PM
Posted 07/13/2010 06:11PM Opening Post
Hi everyone... I'm looking at the 18mm orthos by University Optics (both the volcano tops and HD versions) and the Baader 18mm ortho. Does anyone know whether these eyepieces have enough "functional" eye relief that someone wearing glasses can see the entire field?

Thanks in advance,
John
Posted 07/13/2010 06:48PM | Edited 07/13/2010 06:49PM #1
Hi John,
I do not wear glasses while observing, but my experience with the UO 18mm would indicate that you would have enough eye relief, but best would be the Volcano Top version. The HD has a flat top and that would not be as good for your purpose.
I never measured it, but it was probably about 15-16mm in eye relief.

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Posted 07/13/2010 08:36PM #2
I've got the 18mm UO ortho as well as the 12.5 and the 6mm. Here are the specs from a websource:
http://www.tomhole.com/UO%20Orthos.htm
I think 12mm seems about right for the ER. It's probably doable with thin glasses but I don't wear glasses so I can't say for sure...
Posted 07/18/2010 05:15PM | Edited 07/19/2010 06:03AM #3
I've 25, 18, 12.5 & 9mm in the older volcano-top Circle-T ortho's. The eye lens is recessed down into the barrel so the 18mm just *fits* for a full FOV with my glasses hitting the metal, but it is not comfortable. And with glasses-On I cannot view the entire FOV when using the 12.5mm or 9mm. But, you do not need to wear glasses to view thru a scope (& shouldn't, in order to maximize observed detail) unless you also have Astigmatism. Or file the extraneous metal away to permit a more generous eye relief.
Posted 07/19/2010 09:26AM #4