A Tele Vue 12mm Delos in the Sky-Watcher Evostar 80ED gives 50x, a 1.44 degree true field and a 1.6 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 12mm Delos in the Sky-Watcher Evostar 80ED: magnification and field

What the Tele Vue 12mm Delos does in the Sky-Watcher Evostar 80ED, worked from the published focal lengths and apparent field.

Field of view

ring = 1.44 degrees true
dot = 1.6 mm exit pupil

Computed optics

Magnification
50x600 mm / 12 mm
True field
1.44 degrees72 deg / 50x
Exit pupil
1.6 mm80 mm / 50x
Max useful mag
189xpublished
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Evostar 80ED the Tele Vue 12mm Delos gives 50x with a 1.44 degree true field and a 1.6 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 600 mm divided by 12 mm is 50x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 1.44 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 80 mm over 50x, which is 1.6 mm. That makes this a medium-power general setting.

The eyepiece to buy

Shop Tele Vue 12mm Delos on AmazonaffiliateFind Tele Vue 12mm Delos on eBayaffiliate

Related

Sky-Watcher Evostar 80ED80 mm f/7.5
Tele Vue 12mm Delos12 mm, 72 deg
Best eyepiece for the Sky-Watcher Evostar 80EDexit-pupil match

Questions and answers

Tele Vue 12mm Delos in the Sky-Watcher Evostar 80ED: magnification and field?

Good fit. In the Sky-Watcher Evostar 80ED the Tele Vue 12mm Delos gives 50x with a 1.44 degree true field and a 1.6 mm exit pupil, inside the telescope's useful range.