Optical reference
Tele Vue 7mm Nagler Type 6: focal length, field and the magnification it gives
What the Tele Vue 7mm Nagler Type 6 measures and the magnification and true field it produces once you drop it into a telescope of a given focal length.
Published specifications
An eyepiece has no magnification of its own. The Tele Vue 7mm Nagler Type 6 gives 93x in a 650 mm scope, 171x in a 1200 mm scope, 290x in a 2032 mm scope, because magnification is the telescope's focal length divided by this eyepiece's 7 mm focal length.
Its 82 degree apparent field becomes the true field of view once divided by that magnification: wider in a short-focal-length scope, narrower in a long one. The exit pupil equals this 7 mm focal length divided by the telescope's focal ratio, so at f/5 the exit pupil is 1.4 mm and at f/10 it is 0.7 mm.
The 1.25 in barrel decides which focusers it fits: a 1.25 in barrel fits both dedicated 1.25 in focusers and the 1.25 in adapter of a 2 in focuser.