Optical reference
Orion SkyQuest XT8 Classic Dobsonian: aperture, focal length and eyepiece fit
What the Orion SkyQuest XT8 Classic Dobsonian 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 |
|---|---|---|
| Celestron Omni 4mm Plossl in the Orion SkyQuest XT8 Classic Dobsonian | 300x | 0.17 deg |
| Celestron Omni 12mm Plossl in the Orion SkyQuest XT8 Classic Dobsonian | 100x | 0.5 deg |
The XT8 was for years the default recommendation for a first serious telescope: 203 mm of aperture at 1200 mm f/5.9 on a Dobsonian base. It gathers 73% more light than a 6 in and takes 2 in eyepieces through its Crayford focuser.
Because magnification is the telescope's 1200 mm focal length divided by the eyepiece focal length, a 25 mm eyepiece gives 48x here and a 10 mm eyepiece gives 120x. The highest useful magnification is about 406x (roughly twice the aperture in millimetres), 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.