A Celestron X-Cel LX 18mm in the Celestron StarSense Explorer DX 102AZ gives 37x, a 1.64 degree true field and a 2.8 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 18mm in the Celestron StarSense Explorer DX 102AZ: magnification and field

What the Celestron X-Cel LX 18mm does in the Celestron StarSense Explorer DX 102AZ, worked from the published focal lengths and apparent field.

Field of view

ring = 1.64 degrees true
dot = 2.8 mm exit pupil

Computed optics

Magnification
37x660 mm / 18 mm
True field
1.64 degrees60 deg / 37x
Exit pupil
2.8 mm102 mm / 37x
Max useful mag
241xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
Fits

Good fit. In the Celestron StarSense Explorer DX 102AZ the Celestron X-Cel LX 18mm gives 37x with a 1.64 degree true field and a 2.8 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 660 mm divided by 18 mm is 37x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 1.64 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 102 mm over 37x, which is 2.8 mm. That makes this a medium-power general setting.

The eyepiece to buy

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Related

Celestron StarSense Explorer DX 102AZ102 mm f/6.5
Celestron X-Cel LX 18mm18 mm, 60 deg
Best eyepiece for the Celestron StarSense Explorer DX 102AZexit-pupil match

Questions and answers

Celestron X-Cel LX 18mm in the Celestron StarSense Explorer DX 102AZ: magnification and field?

Good fit. In the Celestron StarSense Explorer DX 102AZ the Celestron X-Cel LX 18mm gives 37x with a 1.64 degree true field and a 2.8 mm exit pupil, inside the telescope's useful range.