TeleVue Radian

More Information  · Recommended Accessories  · Images of Some Features Price $237.00 $250.00 SAVE: $13.00 (5%) List Price $295.00 Field of view 60° Eye Relief 20mm Focal Length 5mm Number of optical elements 7 Barrel Size 1.25" Weight 9 oz Warranty 5 years Telescope Eyepiece Formula To calculate the magnification and approximate actual field of view of this eyepiece on your telescope, enter the focal length of your telescope below and press the "Calculate" button. mm

It will generally be useful with long focal length refractors, reflectors, or catadioptric scopes only under very good or better seeing conditions. Average seeing conditions would limit its usefulness. Using it with a 2000mm 8" f/10 Schmidt-Cassegrain, for example, will result in 400x (50x per inch of aperture) and a 0.5mm exit pupil (about 1/50th of an inch across). Both of these are right at the rule of thumb maximum values of magnification per inch of aperture and exit pupil size for usable observing under good to very good seeing conditions for a reasonably experienced observer.