A Tele Vue 13mm Nagler Type 6 in the Celestron Astro Fi 130 gives 50x, a 1.64 degree true field and a 2.6 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 13mm Nagler Type 6 in the Celestron Astro Fi 130: magnification and field

What the Tele Vue 13mm Nagler Type 6 does in the Celestron Astro Fi 130, worked from the published focal lengths and apparent field.

Field of view

ring = 1.64 degrees true
dot = 2.6 mm exit pupil

Computed optics

Magnification
50x650 mm / 13 mm
True field
1.64 degrees82 deg / 50x
Exit pupil
2.6 mm130 mm / 50x
Max useful mag
307xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
Fits

Good fit. In the Celestron Astro Fi 130 the Tele Vue 13mm Nagler Type 6 gives 50x with a 1.64 degree true field and a 2.6 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 650 mm divided by 13 mm is 50x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 1.64 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 130 mm over 50x, which is 2.6 mm. That makes this a medium-power general setting.

The eyepiece to buy

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Questions and answers

Tele Vue 13mm Nagler Type 6 in the Celestron Astro Fi 130: magnification and field?

Good fit. In the Celestron Astro Fi 130 the Tele Vue 13mm Nagler Type 6 gives 50x with a 1.64 degree true field and a 2.6 mm exit pupil, inside the telescope's useful range.