On Sat, 20 Aug 2011 22:25:29 -0700 (PDT), Ron Cuaz
wrote:

Why did you use 60 degree per radian? is there a particular
significant like maybe some relativistic correction? Just curious why
you need to use 60 instead of 57 since typing 2 numbers in calculator
requires same effort. Thanks.

I'm not sure what you're talking about. I'm not using radians at all.
12.7 arcmin is 0.212 degrees. The formula I gave for subtended angle
is basic trig (it works for any angle, unlike what Paul provided,
which is only for small angles). You can use either radians or degrees
in the formula, as you prefer, but there's no need to do any
conversions, and I didn't.