A Tele Vue 13mm Ethos in the Celestron NexStar Evolution 8 gives 156x, a 0.64 degree true field and a 1.3 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 13mm Ethos in the Celestron NexStar Evolution 8: magnification and field

What the Tele Vue 13mm Ethos does in the Celestron NexStar Evolution 8, worked from the published focal lengths and apparent field.

Field of view

ring = 0.64 degrees true
dot = 1.3 mm exit pupil

Computed optics

Magnification
156x2032 mm / 13 mm
True field
0.64 degrees100 deg / 156x
Exit pupil
1.3 mm203 mm / 156x
Max useful mag
480xpublished
Barrel match
2 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron NexStar Evolution 8 the Tele Vue 13mm Ethos gives 156x with a 0.64 degree true field and a 1.3 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 2032 mm divided by 13 mm is 156x. The true field of view is the eyepiece's 100 degree apparent field divided by that magnification, 0.64 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 203 mm over 156x, which is 1.3 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

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Related

Celestron NexStar Evolution 8203 mm f/10
Tele Vue 13mm Ethos13 mm, 100 deg
Best eyepiece for the Celestron NexStar Evolution 8exit-pupil match

Questions and answers

Tele Vue 13mm Ethos in the Celestron NexStar Evolution 8: magnification and field?

Good fit. In the Celestron NexStar Evolution 8 the Tele Vue 13mm Ethos gives 156x with a 0.64 degree true field and a 1.3 mm exit pupil, inside the telescope's useful range.