Eyepiece and telescope pairing

Celestron X-Cel LX 2.3mm in the Sky-Watcher Heritage 130P: magnification and field

What the Celestron X-Cel LX 2.3mm does in the Sky-Watcher Heritage 130P, worked from the published focal lengths and apparent field.

Field of view

ring = 0.21 degrees true
dot = 0.5 mm exit pupil

Computed optics

Magnification
283x650 mm / 2.3 mm
True field
0.21 degrees60 deg / 283x
Exit pupil
0.5 mm130 mm / 283x
Max useful mag
about 260x2x aperture
Barrel match
1.25 in eyepiece in a 1.25 in focuser
No fit

Over-powered. At 283x this pair exceeds the highest useful magnification of about 260x for the Sky-Watcher Heritage 130P, 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: 650 mm divided by 2.3 mm is 283x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.21 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 130 mm over 283x, which is 0.5 mm. That makes this a high-power lunar, planetary and double-star setting.