A Tele Vue 10mm Ethos in the Sky-Watcher Skymax 102 gives 130x, a 0.77 degree true field and a 0.8 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 Ethos in the Sky-Watcher Skymax 102: magnification and field

What the Tele Vue 10mm Ethos does in the Sky-Watcher Skymax 102, worked from the published focal lengths and apparent field.

Field of view

ring = 0.77 degrees true
dot = 0.8 mm exit pupil

Computed optics

Magnification
130x1300 mm / 10 mm
True field
0.77 degrees100 deg / 130x
Exit pupil
0.8 mm102 mm / 130x
Max useful mag
about 204x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Skymax 102 the Tele Vue 10mm Ethos gives 130x with a 0.77 degree true field and a 0.8 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 1300 mm divided by 10 mm is 130x. The true field of view is the eyepiece's 100 degree apparent field divided by that magnification, 0.77 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 102 mm over 130x, which is 0.8 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

Shop Tele Vue 10mm Ethos on AmazonaffiliateFind Tele Vue 10mm Ethos on eBayaffiliate

Related

Sky-Watcher Skymax 102102 mm f/12.7
Tele Vue 10mm Ethos10 mm, 100 deg
Best eyepiece for the Sky-Watcher Skymax 102exit-pupil match

Questions and answers

Tele Vue 10mm Ethos in the Sky-Watcher Skymax 102: magnification and field?

Good fit. In the Sky-Watcher Skymax 102 the Tele Vue 10mm Ethos gives 130x with a 0.77 degree true field and a 0.8 mm exit pupil, inside the telescope's useful range.