A Celestron X-Cel LX 7mm in the Sky-Watcher Evostar 72ED gives 60x, a 1 degree true field and a 1.2 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Celestron X-Cel LX 7mm in the Sky-Watcher Evostar 72ED: magnification and field

What the Celestron X-Cel LX 7mm does in the Sky-Watcher Evostar 72ED, worked from the published focal lengths and apparent field.

Field of view

ring = 1 degrees true
dot = 1.2 mm exit pupil

Computed optics

Magnification
60x420 mm / 7 mm
True field
1 degrees60 deg / 60x
Exit pupil
1.2 mm72 mm / 60x
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 X-Cel LX 7mm gives 60x with a 1 degree true field and a 1.2 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 7 mm is 60x. The true field of view is the eyepiece's 60 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, 72 mm over 60x, which is 1.2 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

Shop Celestron X-Cel LX 7mm on AmazonaffiliateFind Celestron X-Cel LX 7mm on eBayaffiliate

Related

Sky-Watcher Evostar 72ED72 mm f/5.8
Celestron X-Cel LX 7mm7 mm, 60 deg
Best eyepiece for the Sky-Watcher Evostar 72EDexit-pupil match

Questions and answers

Celestron X-Cel LX 7mm in the Sky-Watcher Evostar 72ED: magnification and field?

Good fit. In the Sky-Watcher Evostar 72ED the Celestron X-Cel LX 7mm gives 60x with a 1 degree true field and a 1.2 mm exit pupil, inside the telescope's useful range.