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Message: <blockquote data-quote="elkcub" data-source="post: 3485405" data-attributes="member: 14473">HR/5 Audubons are marked 430' or 8.21 deg., giving an apparent field of 69.75 deg.  If they were 8.26 deg. the apparent field would be 70.21 deg. (i.e., 0.46 deg larger).HR/5 Audubon-Kestrels 10x50 are marked 367' or 7.0 deg., giving an apparent field of 70.00 deg.These calculations assume that the advertized magnifications are accurate and don't take distortion into account.  So, in practical terms the two instruments have the same apparent fields.Martin, — to be more specific about the Model 825 Newport we would need to know the first two digits of the s/n (which is the date of manufacture).  There were at least two Newport models made, the first by Kutuba/Katsuma and the second by Hiyoshi Kogaku.  The first had a FOV of 367' and the second a FOV of 420 deg., which are quite different.  The latter would have a whopping apparent field of 80.01.  David, — out of curiosity, what is the s/n on your Newport?  Ed</blockquote>