A Celestron X-Cel LX 12mm in the Sky-Watcher Skymax 127 gives 128x, a 0.47 degree true field and a 1 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 12mm in the Sky-Watcher Skymax 127: magnification and field

What the Celestron X-Cel LX 12mm does in the Sky-Watcher Skymax 127, worked from the published focal lengths and apparent field.

Field of view

ring = 0.47 degrees true
dot = 1 mm exit pupil

Computed optics

Magnification
128x1540 mm / 12 mm
True field
0.47 degrees60 deg / 128x
Exit pupil
1 mm127 mm / 128x
Max useful mag
about 254x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Skymax 127 the Celestron X-Cel LX 12mm gives 128x with a 0.47 degree true field and a 1 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 1540 mm divided by 12 mm is 128x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.47 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 127 mm over 128x, which is 1 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

Shop Celestron X-Cel LX 12mm on AmazonaffiliateFind Celestron X-Cel LX 12mm on eBayaffiliate

Related

Sky-Watcher Skymax 127127 mm f/12.1
Celestron X-Cel LX 12mm12 mm, 60 deg
Best eyepiece for the Sky-Watcher Skymax 127exit-pupil match

Questions and answers

Celestron X-Cel LX 12mm in the Sky-Watcher Skymax 127: magnification and field?

Good fit. In the Sky-Watcher Skymax 127 the Celestron X-Cel LX 12mm gives 128x with a 0.47 degree true field and a 1 mm exit pupil, inside the telescope's useful range.