A Celestron Omni 56mm Plossl in the Celestron C11 optical tube gives 50x, a 0.94 degree true field and a 5.6 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Celestron Omni 56mm Plossl in the Celestron C11 optical tube: magnification and field

What the Celestron Omni 56mm Plossl does in the Celestron C11 optical tube, worked from the published focal lengths and apparent field.

Field of view

ring = 0.94 degrees true
dot = 5.6 mm exit pupil

Computed optics

Magnification
50x2800 mm / 56 mm
True field
0.94 degrees47 deg / 50x
Exit pupil
5.6 mm280 mm / 50x
Max useful mag
660xpublished
Barrel match
2 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron C11 optical tube the Celestron Omni 56mm Plossl gives 50x with a 0.94 degree true field and a 5.6 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 2800 mm divided by 56 mm is 50x. The true field of view is the eyepiece's 47 degree apparent field divided by that magnification, 0.94 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 280 mm over 50x, which is 5.6 mm. That makes this a low-power, wide-field and deep-sky setting.

The eyepiece to buy

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Related

Celestron C11 optical tube280 mm f/10
Celestron Omni 56mm Plossl56 mm, 47 deg
Best eyepiece for the Celestron C11 optical tubeexit-pupil match

Questions and answers

Celestron Omni 56mm Plossl in the Celestron C11 optical tube: magnification and field?

Good fit. In the Celestron C11 optical tube the Celestron Omni 56mm Plossl gives 50x with a 0.94 degree true field and a 5.6 mm exit pupil, inside the telescope's useful range.