A Tele Vue 12mm Delos in the Celestron C11 optical tube gives 233x, a 0.31 degree true field and a 1.2 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 12mm Delos in the Celestron C11 optical tube: magnification and field

What the Tele Vue 12mm Delos does in the Celestron C11 optical tube, worked from the published focal lengths and apparent field.

Field of view

ring = 0.31 degrees true
dot = 1.2 mm exit pupil

Computed optics

Magnification
233x2800 mm / 12 mm
True field
0.31 degrees72 deg / 233x
Exit pupil
1.2 mm280 mm / 233x
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 12mm Delos gives 233x with a 0.31 degree true field and a 1.2 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 12 mm is 233x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 0.31 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 280 mm over 233x, which is 1.2 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

Shop Tele Vue 12mm Delos on AmazonaffiliateFind Tele Vue 12mm Delos on eBayaffiliate

Related

Celestron C11 optical tube280 mm f/10
Tele Vue 12mm Delos12 mm, 72 deg
Best eyepiece for the Celestron C11 optical tubeexit-pupil match

Questions and answers

Tele Vue 12mm Delos in the Celestron C11 optical tube: magnification and field?

Good fit. In the Celestron C11 optical tube the Tele Vue 12mm Delos gives 233x with a 0.31 degree true field and a 1.2 mm exit pupil, inside the telescope's useful range.