A Tele Vue 17mm Ethos in the Celestron NexStar 8SE gives 120x, a 0.84 degree true field and a 1.7 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 17mm Ethos in the Celestron NexStar 8SE: magnification and field

What the Tele Vue 17mm Ethos does in the Celestron NexStar 8SE, worked from the published focal lengths and apparent field.

Field of view

ring = 0.84 degrees true
dot = 1.7 mm exit pupil

Computed optics

Magnification
120x2032 mm / 17 mm
True field
0.84 degrees100 deg / 120x
Exit pupil
1.7 mm203 mm / 120x
Max useful mag
480xpublished
Barrel match
2 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron NexStar 8SE the Tele Vue 17mm Ethos gives 120x with a 0.84 degree true field and a 1.7 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 17 mm is 120x. The true field of view is the eyepiece's 100 degree apparent field divided by that magnification, 0.84 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 203 mm over 120x, which is 1.7 mm. That makes this a medium-power general setting.

The eyepiece to buy

Shop Tele Vue 17mm Ethos on AmazonaffiliateFind Tele Vue 17mm Ethos on eBayaffiliate

Related

Celestron NexStar 8SE203 mm f/10
Tele Vue 17mm Ethos17 mm, 100 deg
Best eyepiece for the Celestron NexStar 8SEexit-pupil match

Questions and answers

Tele Vue 17mm Ethos in the Celestron NexStar 8SE: magnification and field?

Good fit. In the Celestron NexStar 8SE the Tele Vue 17mm Ethos gives 120x with a 0.84 degree true field and a 1.7 mm exit pupil, inside the telescope's useful range.