Eyepiece and telescope pairing
Celestron Omni 15mm Plossl in the Orion SkyQuest XT12 Classic Dobsonian: magnification and field
What the Celestron Omni 15mm Plossl does in the Orion SkyQuest XT12 Classic Dobsonian, worked from the published focal lengths and apparent field.
Field of view
ring = 0.5 degrees true
dot = 3 mm exit pupil
- Magnification
- 100x1500 mm / 15 mm
- True field
- 0.5 degrees50 deg / 100x
- Exit pupil
- 3 mm305 mm / 100x
- Max useful mag
- about 610x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Good fit. In the Orion SkyQuest XT12 Classic Dobsonian the Celestron Omni 15mm Plossl gives 100x with a 0.5 degree true field and a 3 mm exit pupil, inside the telescope's useful range.
Magnification is the telescope focal length divided by the eyepiece focal length: 1500 mm divided by 15 mm is 100x. The true field of view is the eyepiece's 50 degree apparent field divided by that magnification, 0.5 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 305 mm over 100x, which is 3 mm. That makes this a medium-power general setting.
The eyepiece to buy
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