Optical reference
Celestron Omni XLT 120: aperture, focal length and eyepiece fit
What the Celestron Omni XLT 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 Celestron Omni XLT 120 | 200x | 0.41 deg |
| Tele Vue 17mm Ethos in the Celestron Omni XLT 120 | 59x | 1.7 deg |
The Omni XLT 120 is a 120 mm f/8.3 achromatic refractor on an equatorial mount. Its 1000 mm focal length keeps false colour modest for the class and its 2 in focuser takes long low-power eyepieces.
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.