Eyepiece and telescope pairing
Celestron X-Cel LX 2.3mm in the Celestron Omni XLT 120: magnification and field
What the Celestron X-Cel LX 2.3mm does in the Celestron Omni XLT 120, worked from the published focal lengths and apparent field.
Field of view
ring = 0.14 degrees true
dot = 0.3 mm exit pupil
- Magnification
- 435x1000 mm / 2.3 mm
- True field
- 0.14 degrees60 deg / 435x
- Exit pupil
- 0.3 mm120 mm / 435x
- Max useful mag
- 283xpublished
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Over-powered. At 435x this pair exceeds the published highest useful magnification of about 283x for the Celestron Omni XLT 120, 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, 120 mm over 435x, which is 0.3 mm. That makes this a high-power lunar, planetary and double-star setting.
The eyepiece to buy
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