Eyepiece and telescope pairing

Celestron X-Cel LX 2.3mm in the Celestron StarSense Explorer LT 80AZ: magnification and field

What the Celestron X-Cel LX 2.3mm does in the Celestron StarSense Explorer LT 80AZ, worked from the published focal lengths and apparent field.

Field of view

ring = 0.15 degrees true
dot = 0.2 mm exit pupil

Computed optics

Magnification
391x900 mm / 2.3 mm
True field
0.15 degrees60 deg / 391x
Exit pupil
0.2 mm80 mm / 391x
Max useful mag
189xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
No fit

Over-powered. At 391x this pair exceeds the published highest useful magnification of about 189x for the Celestron StarSense Explorer LT 80AZ, so the image dims and softens without showing more real detail. Use a longer eyepiece.


Magnification is the telescope focal length divided by the eyepiece focal length: 900 mm divided by 2.3 mm is 391x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.15 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 80 mm over 391x, which is 0.2 mm. That makes this a high-power lunar, planetary and double-star setting.