Eyepiece and telescope pairing
Tele Vue 10mm Ethos in the Celestron Omni XLT 120: magnification and field
What the Tele Vue 10mm Ethos does in the Celestron Omni XLT 120, worked from the published focal lengths and apparent field.
Field of view
ring = 1 degrees true
dot = 1.2 mm exit pupil
- Magnification
- 100x1000 mm / 10 mm
- True field
- 1 degrees100 deg / 100x
- Exit pupil
- 1.2 mm120 mm / 100x
- Max useful mag
- 283xpublished
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Good fit. In the Celestron Omni XLT 120 the Tele Vue 10mm Ethos gives 100x with a 1 degree true field and a 1.2 mm exit pupil, inside the telescope's useful range.
Magnification is the telescope focal length divided by the eyepiece focal length: 1000 mm divided by 10 mm is 100x. The true field of view is the eyepiece's 100 degree apparent field divided by that magnification, 1 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 120 mm over 100x, which is 1.2 mm. That makes this a high-power lunar, planetary and double-star setting.
The eyepiece to buy
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