Eyepiece and telescope pairing

Celestron Omni 6mm Plossl in the Orion SkyQuest XT8 Classic Dobsonian: magnification and field

What the Celestron Omni 6mm Plossl does in the Orion SkyQuest XT8 Classic Dobsonian, worked from the published focal lengths and apparent field.

Field of view

ring = 0.25 degrees true
dot = 1 mm exit pupil

Computed optics

Magnification
200x1200 mm / 6 mm
True field
0.25 degrees50 deg / 200x
Exit pupil
1 mm203 mm / 200x
Max useful mag
about 406x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Orion SkyQuest XT8 Classic Dobsonian the Celestron Omni 6mm Plossl gives 200x with a 0.25 degree true field and a 1 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 6 mm is 200x. The true field of view is the eyepiece's 50 degree apparent field divided by that magnification, 0.25 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 203 mm over 200x, which is 1 mm. That makes this a high-power lunar, planetary and double-star setting.