Optical reference
Celestron C5 optical tube: aperture, focal length and eyepiece fit
What the Celestron C5 optical tube 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 6mm Plossl in the Celestron C5 optical tube | 208x | 0.24 deg |
| Tele Vue 20mm Plossl in the Celestron C5 optical tube | 62x | 0.8 deg |
The C5 is a compact 127 mm f/10 Schmidt-Cassegrain tube, the same optics found in the 5SE, sold bare as a spotting and grab-and-go astronomy tube. Its 1250 mm focal length gives contrasty lunar and planetary views in a very short, light package.
Because magnification is the telescope's 1250 mm focal length divided by the eyepiece focal length, a 25 mm eyepiece gives 50x here and a 10 mm eyepiece gives 125x. The highest useful magnification is the published 295x, beyond which the image dims and softens without showing more detail.
The focuser takes 1.25 in eyepieces, so use 1.25 in eyepieces; a long low-power 2 in eyepiece will not fit this focuser.