A Tele Vue 10mm Delos in the Celestron C11 optical tube gives 280x, a 0.26 degree true field and a 1 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 10mm Delos in the Celestron C11 optical tube: magnification and field

What the Tele Vue 10mm Delos does in the Celestron C11 optical tube, worked from the published focal lengths and apparent field.

Field of view

ring = 0.26 degrees true
dot = 1 mm exit pupil

Computed optics

Magnification
280x2800 mm / 10 mm
True field
0.26 degrees72 deg / 280x
Exit pupil
1 mm280 mm / 280x
Max useful mag
660xpublished
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron C11 optical tube the Tele Vue 10mm Delos gives 280x with a 0.26 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: 2800 mm divided by 10 mm is 280x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 0.26 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 280 mm over 280x, which is 1 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

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Related

Celestron C11 optical tube280 mm f/10
Tele Vue 10mm Delos10 mm, 72 deg
Best eyepiece for the Celestron C11 optical tubeexit-pupil match

Questions and answers

Tele Vue 10mm Delos in the Celestron C11 optical tube: magnification and field?

Good fit. In the Celestron C11 optical tube the Tele Vue 10mm Delos gives 280x with a 0.26 degree true field and a 1 mm exit pupil, inside the telescope's useful range.