Eyepiece and telescope pairing
Celestron X-Cel LX 5mm in the Sky-Watcher Skymax 127: magnification and field
What the Celestron X-Cel LX 5mm does in the Sky-Watcher Skymax 127, worked from the published focal lengths and apparent field.
Field of view
ring = 0.19 degrees true
dot = 0.4 mm exit pupil
- Magnification
- 308x1540 mm / 5 mm
- True field
- 0.19 degrees60 deg / 308x
- Exit pupil
- 0.4 mm127 mm / 308x
- Max useful mag
- about 254x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Over-powered. At 308x this pair exceeds the highest useful magnification of about 254x for the Sky-Watcher Skymax 127, 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: 1540 mm divided by 5 mm is 308x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.19 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 127 mm over 308x, which is 0.4 mm. That makes this a high-power lunar, planetary and double-star setting.
The eyepiece to buy
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