Eyepiece and telescope pairing

Celestron Omni 12mm Plossl in the Celestron NexStar 4SE: magnification and field

What the Celestron Omni 12mm Plossl does in the Celestron NexStar 4SE, worked from the published focal lengths and apparent field.

Field of view

ring = 0.45 degrees true
dot = 0.9 mm exit pupil

Computed optics

Magnification
110x1325 mm / 12 mm
True field
0.45 degrees50 deg / 110x
Exit pupil
0.9 mm102 mm / 110x
Max useful mag
241xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
Fits

Good fit. In the Celestron NexStar 4SE the Celestron Omni 12mm Plossl gives 110x with a 0.45 degree true field and a 0.9 mm exit pupil, inside the telescope's useful range.


Magnification is the telescope focal length divided by the eyepiece focal length: 1325 mm divided by 12 mm is 110x. The true field of view is the eyepiece's 50 degree apparent field divided by that magnification, 0.45 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 102 mm over 110x, which is 0.9 mm. That makes this a high-power lunar, planetary and double-star setting.