Optical reference
Celestron Astro Fi 102: aperture, focal length and eyepiece fit
What the Celestron Astro Fi 102 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 8mm Plossl in the Celestron Astro Fi 102 | 166x | 0.3 deg |
| Celestron X-Cel LX 25mm in the Celestron Astro Fi 102 | 53x | 1.13 deg |
The Astro Fi 102 is a 102 mm f/13 Maksutov on a phone-controlled WiFi mount. The long 1325 mm focal length in a short sealed tube gives crisp lunar and planetary detail, with deep-sky reach limited by the small aperture.
Because magnification is the telescope's 1325 mm focal length divided by the eyepiece focal length, a 25 mm eyepiece gives 53x here and a 10 mm eyepiece gives 132x. The highest useful magnification is the published 241x, 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.