Eyepiece and telescope pairing
Celestron X-Cel LX 2.3mm in the Sky-Watcher Classic 200P (8-inch Dobsonian): magnification and field
What the Celestron X-Cel LX 2.3mm does in the Sky-Watcher Classic 200P (8-inch Dobsonian), worked from the published focal lengths and apparent field.
Field of view
ring = 0.11 degrees true
dot = 0.4 mm exit pupil
- Magnification
- 522x1200 mm / 2.3 mm
- True field
- 0.11 degrees60 deg / 522x
- Exit pupil
- 0.4 mm203 mm / 522x
- Max useful mag
- about 406x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Over-powered. At 522x this pair exceeds the highest useful magnification of about 406x for the Sky-Watcher Classic 200P (8-inch Dobsonian), 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: 1200 mm divided by 2.3 mm is 522x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.11 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 203 mm over 522x, 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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