Eyepiece and telescope pairing
Best eyepiece for the Celestron C5 optical tube
Which eyepiece gets the most out of the Celestron C5 optical tube, chosen by exit pupil rather than by guesswork.
- Aperture / focal length
- 127 mm / 1250 mm (f/10)
- Deep-sky pick
- Tele Vue 20mm Plossl: 62x, 2.03 mm exit pupil
- Low-power pick
- Celestron Omni 40mm Plossl: 31x, 4.06 mm exit pupil
- Focuser barrel
- 1.25 in (both eyepieces fit)
For deep-sky detail, the Tele Vue 20mm Plossl is the pick of the eyepieces here: at 62x it lands near the 2 mm exit pupil where faint-object contrast peaks in the Celestron C5 optical tube. For wide low-power sweeping, drop to the Celestron Omni 40mm Plossl at 31x.
An exit pupil near 2 mm is the classic sweet spot for teasing detail out of faint deep-sky objects, because it concentrates the light while keeping the image bright enough. In the Celestron C5 optical tube the Tele Vue 20mm Plossl lands there, at 62x with a 2.03 mm exit pupil and a 0.8 degree field.
For a low-power finder-and-framing view you want a wider exit pupil, around 5 mm. Here the Celestron Omni 40mm Plossl gives 31x, a 4.06 mm exit pupil and a 1.28 degree field, the widest true field of the eyepieces that fit this focuser.