Eyepiece and telescope pairing

Celestron X-Cel LX 2.3mm in the Celestron PowerSeeker 127EQ: magnification and field

What the Celestron X-Cel LX 2.3mm does in the Celestron PowerSeeker 127EQ, worked from the published focal lengths and apparent field.

Field of view

ring = 0.14 degrees true
dot = 0.3 mm exit pupil

Computed optics

Magnification
435x1000 mm / 2.3 mm
True field
0.14 degrees60 deg / 435x
Exit pupil
0.3 mm127 mm / 435x
Max useful mag
300xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
No fit

Over-powered. At 435x this pair exceeds the published highest useful magnification of about 300x for the Celestron PowerSeeker 127EQ, 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: 1000 mm divided by 2.3 mm is 435x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.14 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 127 mm over 435x, which is 0.3 mm. That makes this a high-power lunar, planetary and double-star setting.