A Celestron Omni 12mm Plossl in the Sky-Watcher Evostar 80ED gives 50x, a 1 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

Celestron Omni 12mm Plossl in the Sky-Watcher Evostar 80ED: magnification and field

What the Celestron Omni 12mm Plossl does in the Sky-Watcher Evostar 80ED, worked from the published focal lengths and apparent field.

Field of view

ring = 1 degrees true
dot = 1.6 mm exit pupil

Computed optics

Magnification
50x600 mm / 12 mm
True field
1 degrees50 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 Celestron Omni 12mm Plossl gives 50x with a 1 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 50 degree apparent field divided by that magnification, 1 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

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Related

Sky-Watcher Evostar 80ED80 mm f/7.5
Celestron Omni 12mm Plossl12 mm, 50 deg
Best eyepiece for the Sky-Watcher Evostar 80EDexit-pupil match

Questions and answers

Celestron Omni 12mm Plossl in the Sky-Watcher Evostar 80ED: magnification and field?

Good fit. In the Sky-Watcher Evostar 80ED the Celestron Omni 12mm Plossl gives 50x with a 1 degree true field and a 1.6 mm exit pupil, inside the telescope's useful range.