Re: ATM Televue eyepiece data

[Bratislav Curcic <epabcc@epa.ericsson.se>]

michael pankratz wrote 

> the 16 nagler, sad to say, worked out to only ( ! ) 73 degrees.

There is, unfortunately, NO 'standard' in how to define eyepiece's
apparent field of view. One way (the most direct one!) is as Michael
did, by measuring the angle that field stop subtends to. But there's
more to the story. All eyepieces (Naglers included) will suffer from
distortion (i.e. square objects don't look square anymore when looked 
thru an eyepiece). This has to be taken into account SOMEHOW when
field of view is specified (as eyepiece may 'squeeze' more image
close to the field stop, effectively behaving as AFOV was larger).
This is where I believe Al Nagler 'adjusted' AFOV's of Naglers. In any
case, when these eyepieces appeared, he didn't have competition to cheat
on by specifying 2 degrees more; the closest wide angles were way narrower
and MUCH worse.
But as already said, who cares. 73, 81, 83 ... big deal. They are the
WIDEST and BEST corrected eyepieces one can buy today. If I could just
convince my wife to buy me a set for a birthday ...

Bratislav