Eyepiece and telescope pairing
Celestron X-Cel LX 18mm in the Orion SkyQuest XT10 Classic Dobsonian: magnification and field
What the Celestron X-Cel LX 18mm does in the Orion SkyQuest XT10 Classic Dobsonian, worked from the published focal lengths and apparent field.
Field of view
ring = 0.9 degrees true
dot = 3.8 mm exit pupil
- Magnification
- 67x1200 mm / 18 mm
- True field
- 0.9 degrees60 deg / 67x
- Exit pupil
- 3.8 mm254 mm / 67x
- Max useful mag
- about 508x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Good fit. In the Orion SkyQuest XT10 Classic Dobsonian the Celestron X-Cel LX 18mm gives 67x with a 0.9 degree true field and a 3.8 mm exit pupil, inside the telescope's useful range.
Magnification is the telescope focal length divided by the eyepiece focal length: 1200 mm divided by 18 mm is 67x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 0.9 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 254 mm over 67x, which is 3.8 mm. That makes this a medium-power general setting.
The eyepiece to buy
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