SingAstro

~20mm of eye relief is generally regarded as comfortable. It really depends on what you are comfortable, and can "tahan", though. Some people may find short ef eps acceptable. Others would avoid them. I suggest you try eps in other pple scope to determine what ef you are acceptable with.

Sometimes, too much eye relief is not good because you have to position your eye awkwardly quite far away from the eye lens to see the whole FOV.

However, most people have more issue with short eye relief, its generally uncomfortable to put your eye so close to the eye lens. Also, you don't want your eyelashes to touch your lens!

For small objects, eye relief isn't so important. Even in very short focal length eyepieces with very short eye relief, small objects are often visible at quite a distance, say 20mm to 30mm, away from the eyepiece. This leads to the conclusion that when viewing small objects, FOV and eye relief for any given eyepiece become far less important.

For a guide to eye relief, got an excellent article on ef on cloudy nights. This will give you a good guide to see what specific range of eye relief you like.

http://www.cloudynights.net/howtos2/eyerelief.htm

It also depend on the magnifications. If ur scope is a rich field scope with f-ratio f5 or below, the magnification using a short focal length eps is still quite low thus E.R. may not be a issue.

hey im not the only one with astig ^_^

just a qns:

if your eyepiece has, say 30mm eye relief...
and u place you eye 20mm from the eye lens...
will u still see the entire fov or will there be vignetting?

err..binos hor, i doubt u have to worry abt eye relief that much. my 12x50 binos have a little too much eye relief, if i dun use the eyecup, the images tend to blackout alot.

another thing, using binos without ur glasses on is a major pain. firstly u won't know where u are pointing when looking thru the binos. u take off the binos and try to figure out where u are seeing with ur eyes, and u will see nothing, everything is blurred.

eyepieces for scope, the eye relief becomes an important factor, esp eyepieces 12.5mm and below. a typical eyepiece have ard 80% of the focal length as it's eye relief. so a 10mm plossl might have 8mm of eye relief >.< as such, i recommend that u spend more money and get the premium long eye relief stuff or barlow ur way through.

~MooEy~

just a qns:

if your eyepiece has, say 30mm eye relief...
and u place you eye 20mm from the eye lens...
will u still see the entire fov or will there be vignetting?

Yes, there will be blackout.(not sure if it is called vignetting in this case) You won't be able to see the entire FOV.

nope, not vignetting, just blackout.

~MooEy~