Optical reference
Sky-Watcher Evostar 120: aperture, focal length and eyepiece fit
What the Sky-Watcher Evostar 120 measures, the magnification and true field each eyepiece produces in it, and the barrel, mount payload and camera adapter that fit.
Published specifications
Eyepiece ladder
2 pairings| Pairing | Magnification | True field |
|---|---|---|
| Tele Vue 5mm Nagler Type 6 in the Sky-Watcher Evostar 120 | 200x | 0.41 deg |
| Tele Vue 17mm Ethos in the Sky-Watcher Evostar 120 | 59x | 1.7 deg |
The Evostar 120 is a 120 mm f/8.3 achromatic refractor with an 1000 mm focal length. The larger aperture reaches fainter detail than an 80 mm, and the slower focal ratio keeps false colour modest for an achromat.
Because magnification is the telescope's 1000 mm focal length divided by the eyepiece focal length, a 25 mm eyepiece gives 40x here and a 10 mm eyepiece gives 100x. The highest useful magnification is the published 283x, beyond which the image dims and softens without showing more detail.
The focuser takes 2 in eyepieces, so long 2 in wide-field eyepieces such as the Omni 56 mm fit as well as 1.25 in ones.