Eyepiece and telescope pairing
Tele Vue 2.5mm Nagler Type 6 in the Celestron C8 optical tube: magnification and field
What the Tele Vue 2.5mm Nagler Type 6 does in the Celestron C8 optical tube, worked from the published focal lengths and apparent field.
Field of view
ring = 0.1 degrees true
dot = 0.2 mm exit pupil
- Magnification
- 813x2032 mm / 2.5 mm
- True field
- 0.1 degrees82 deg / 813x
- Exit pupil
- 0.2 mm203 mm / 813x
- Max useful mag
- 480xpublished
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Over-powered. At 813x this pair exceeds the published highest useful magnification of about 480x for the Celestron C8 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: 2032 mm divided by 2.5 mm is 813x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 0.1 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 203 mm over 813x, which is 0.2 mm. That makes this a high-power lunar, planetary and double-star setting.
The eyepiece to buy
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