A Explore Scientific 30mm 82 Degree in the Celestron C11 optical tube gives 93x, a 0.88 degree true field and a 3 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Explore Scientific 30mm 82 Degree in the Celestron C11 optical tube: magnification and field

What the Explore Scientific 30mm 82 Degree does in the Celestron C11 optical tube, worked from the published focal lengths and apparent field.

Field of view

ring = 0.88 degrees true
dot = 3 mm exit pupil

Computed optics

Magnification
93x2800 mm / 30 mm
True field
0.88 degrees82 deg / 93x
Exit pupil
3 mm280 mm / 93x
Max useful mag
660xpublished
Barrel match
2 in eyepiece in a 2 in focuser
Fits

Good fit. In the Celestron C11 optical tube the Explore Scientific 30mm 82 Degree gives 93x with a 0.88 degree true field and a 3 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 2800 mm divided by 30 mm is 93x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 0.88 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 280 mm over 93x, which is 3 mm. That makes this a medium-power general setting.

The eyepiece to buy

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Related

Celestron C11 optical tube280 mm f/10
Explore Scientific 30mm 82 Degree30 mm, 82 deg
Best eyepiece for the Celestron C11 optical tubeexit-pupil match

Questions and answers

Explore Scientific 30mm 82 Degree in the Celestron C11 optical tube: magnification and field?

Good fit. In the Celestron C11 optical tube the Explore Scientific 30mm 82 Degree gives 93x with a 0.88 degree true field and a 3 mm exit pupil, inside the telescope's useful range.