Eyepiece and telescope pairing
Celestron Omni 40mm Plossl in the Orion SkyQuest XT6 Classic Dobsonian: magnification and field
What the Celestron Omni 40mm Plossl does in the Orion SkyQuest XT6 Classic Dobsonian, worked from the published focal lengths and apparent field.
Field of view
ring = 1.33 degrees true
dot = 5 mm exit pupil
- Magnification
- 30x1200 mm / 40 mm
- True field
- 1.33 degrees40 deg / 30x
- Exit pupil
- 5 mm150 mm / 30x
- Max useful mag
- about 300x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 1.25 in focuser
Good fit. In the Orion SkyQuest XT6 Classic Dobsonian the Celestron Omni 40mm Plossl gives 30x with a 1.33 degree true field and a 5 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 40 mm is 30x. The true field of view is the eyepiece's 40 degree apparent field divided by that magnification, 1.33 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 150 mm over 30x, which is 5 mm. That makes this a low-power, wide-field and deep-sky setting.
The eyepiece to buy
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