field stop

[faulksy]

hi just wondered what field stop was all about and how important it is. been looking for a 2" ep to give me the widest possible field of view in my 9.25, i have a burgess 2" fl 38mm fov 70 degrees which if i calculated right gives me tfov 1.13 degrees. looked up the specs for burgess and it says field stop 46mm, what does this mean. is this calculated or measured ?also how wide is the pliedes roughly thanks peeps:confused:

[John]

Have a look at this thread. The last two posts particularly. I think the Burgess 38mm SWA is the same eyepiece as the 38mm Adler Skarp. It certainly looks just the same :

http://stargazerslounge.com/discussions-eyepieces/177387-wider-absolute-field-11-sct.html

The position of the field stop is at the focal plane of the eyepiece but that varies with the eyepiece design. In some cases it's in the eyepiece barrel below last lens (the field lens) and in others (eg: Naglers) the field stop is in the centre of the eyepiece and not readily accessible for measuring.

[faulksy]

thanks john