A Celestron X-Cel LX 9mm in the Sky-Watcher Skymax 180 gives 300x, a 0.2 degree true field and a 0.6 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 9mm in the Sky-Watcher Skymax 180: magnification and field

What the Celestron X-Cel LX 9mm does in the Sky-Watcher Skymax 180, worked from the published focal lengths and apparent field.

Field of view

ring = 0.2 degrees true
dot = 0.6 mm exit pupil

Computed optics

Magnification
300x2700 mm / 9 mm
True field
0.2 degrees60 deg / 300x
Exit pupil
0.6 mm180 mm / 300x
Max useful mag
about 360x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Skymax 180 the Celestron X-Cel LX 9mm gives 300x with a 0.2 degree true field and a 0.6 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 2700 mm divided by 9 mm is 300x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.2 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 180 mm over 300x, which is 0.6 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

Shop Celestron X-Cel LX 9mm on AmazonaffiliateFind Celestron X-Cel LX 9mm on eBayaffiliate

Related

Sky-Watcher Skymax 180180 mm f/15
Celestron X-Cel LX 9mm9 mm, 60 deg
Best eyepiece for the Sky-Watcher Skymax 180exit-pupil match

Questions and answers

Celestron X-Cel LX 9mm in the Sky-Watcher Skymax 180: magnification and field?

Good fit. In the Sky-Watcher Skymax 180 the Celestron X-Cel LX 9mm gives 300x with a 0.2 degree true field and a 0.6 mm exit pupil, inside the telescope's useful range.