Eyepiece and telescope pairing

Celestron X-Cel LX 9mm in the Celestron StarSense Explorer LT 80AZ: magnification and field

What the Celestron X-Cel LX 9mm does in the Celestron StarSense Explorer LT 80AZ, worked from the published focal lengths and apparent field.

Field of view

ring = 0.6 degrees true
dot = 0.8 mm exit pupil

Computed optics

Magnification
100x900 mm / 9 mm
True field
0.6 degrees60 deg / 100x
Exit pupil
0.8 mm80 mm / 100x
Max useful mag
189xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
Fits

Good fit. In the Celestron StarSense Explorer LT 80AZ the Celestron X-Cel LX 9mm gives 100x with a 0.6 degree true field and a 0.8 mm exit pupil, inside the telescope's useful range.


Magnification is the telescope focal length divided by the eyepiece focal length: 900 mm divided by 9 mm is 100x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.6 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 80 mm over 100x, which is 0.8 mm. That makes this a high-power lunar, planetary and double-star setting.