A Celestron Omni 56mm Plossl in the Celestron Omni XLT 120 gives 18x, a 2.63 degree true field and a 6.7 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 Omni XLT 120: magnification and field

What the Celestron Omni 56mm Plossl does in the Celestron Omni XLT 120, worked from the published focal lengths and apparent field.

Field of view

ring = 2.63 degrees true
dot = 6.7 mm exit pupil

Computed optics

Magnification
18x1000 mm / 56 mm
True field
2.63 degrees47 deg / 18x
Exit pupil
6.7 mm120 mm / 18x
Max useful mag
283xpublished
Barrel match
2 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron Omni XLT 120 the Celestron Omni 56mm Plossl gives 18x with a 2.63 degree true field and a 6.7 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 1000 mm divided by 56 mm is 18x. The true field of view is the eyepiece's 47 degree apparent field divided by that magnification, 2.63 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 120 mm over 18x, which is 6.7 mm. That makes this a low-power, wide-field and deep-sky setting.

The eyepiece to buy

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Related

Celestron Omni XLT 120120 mm f/8.3
Celestron Omni 56mm Plossl56 mm, 47 deg
Best eyepiece for the Celestron Omni XLT 120exit-pupil match

Questions and answers

Celestron Omni 56mm Plossl in the Celestron Omni XLT 120: magnification and field?

Good fit. In the Celestron Omni XLT 120 the Celestron Omni 56mm Plossl gives 18x with a 2.63 degree true field and a 6.7 mm exit pupil, inside the telescope's useful range.