A Celestron Omni 9mm Plossl in the Sky-Watcher Evostar 72ED gives 47x, a 1.07 degree true field and a 1.5 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Celestron Omni 9mm Plossl in the Sky-Watcher Evostar 72ED: magnification and field

What the Celestron Omni 9mm Plossl does in the Sky-Watcher Evostar 72ED, worked from the published focal lengths and apparent field.

Field of view

ring = 1.07 degrees true
dot = 1.5 mm exit pupil

Computed optics

Magnification
47x420 mm / 9 mm
True field
1.07 degrees50 deg / 47x
Exit pupil
1.5 mm72 mm / 47x
Max useful mag
170xpublished
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Evostar 72ED the Celestron Omni 9mm Plossl gives 47x with a 1.07 degree true field and a 1.5 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 420 mm divided by 9 mm is 47x. The true field of view is the eyepiece's 50 degree apparent field divided by that magnification, 1.07 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 72 mm over 47x, which is 1.5 mm. That makes this a medium-power general setting.

The eyepiece to buy

Shop Celestron Omni 9mm Plossl on AmazonaffiliateFind Celestron Omni 9mm Plossl on eBayaffiliate

Related

Sky-Watcher Evostar 72ED72 mm f/5.8
Celestron Omni 9mm Plossl9 mm, 50 deg
Best eyepiece for the Sky-Watcher Evostar 72EDexit-pupil match

Questions and answers

Celestron Omni 9mm Plossl in the Sky-Watcher Evostar 72ED: magnification and field?

Good fit. In the Sky-Watcher Evostar 72ED the Celestron Omni 9mm Plossl gives 47x with a 1.07 degree true field and a 1.5 mm exit pupil, inside the telescope's useful range.