Eyepiece and telescope pairing
Celestron X-Cel LX 2.3mm in the Orion SpaceProbe 130ST: magnification and field
What the Celestron X-Cel LX 2.3mm does in the Orion SpaceProbe 130ST, worked from the published focal lengths and apparent field.
Field of view
ring = 0.21 degrees true
dot = 0.5 mm exit pupil
- 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
Computed optics
- Barrel match
- 1.25 in eyepiece in a 1.25 in focuser
Over-powered. At 283x this pair exceeds the highest useful magnification of about 260x for the Orion SpaceProbe 130ST, 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.
The eyepiece to buy
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