Eyepiece and telescope pairing
Tele Vue 2.5mm Nagler Type 6 in the Celestron C5 optical tube: magnification and field
What the Tele Vue 2.5mm Nagler Type 6 does in the Celestron C5 optical tube, worked from the published focal lengths and apparent field.
Field of view
ring = 0.16 degrees true
dot = 0.3 mm exit pupil
- Magnification
- 500x1250 mm / 2.5 mm
- True field
- 0.16 degrees82 deg / 500x
- Exit pupil
- 0.3 mm127 mm / 500x
- Max useful mag
- 295xpublished
Computed optics
- Barrel match
- 1.25 in eyepiece in a 1.25 in focuser
Over-powered. At 500x this pair exceeds the published highest useful magnification of about 295x for the Celestron C5 optical tube, so the image dims and softens without showing more real detail. Use a longer eyepiece.
Magnification is the telescope focal length divided by the eyepiece focal length: 1250 mm divided by 2.5 mm is 500x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 0.16 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 127 mm over 500x, which is 0.3 mm. That makes this a high-power lunar, planetary and double-star setting.
The eyepiece to buy
Shop Tele Vue 2.5mm Nagler Type 6 on AmazonaffiliateFind Tele Vue 2.5mm Nagler Type 6 on eBayaffiliate