A Tele Vue 14mm Delos in the Sky-Watcher Classic 250P (10-inch Dobsonian) gives 86x, a 0.84 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

Tele Vue 14mm Delos in the Sky-Watcher Classic 250P (10-inch Dobsonian): magnification and field

What the Tele Vue 14mm Delos does in the Sky-Watcher Classic 250P (10-inch Dobsonian), worked from the published focal lengths and apparent field.

Field of view

ring = 0.84 degrees true
dot = 3 mm exit pupil

Computed optics

Magnification
86x1200 mm / 14 mm
True field
0.84 degrees72 deg / 86x
Exit pupil
3 mm254 mm / 86x
Max useful mag
about 508x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Classic 250P (10-inch Dobsonian) the Tele Vue 14mm Delos gives 86x with a 0.84 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: 1200 mm divided by 14 mm is 86x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 0.84 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 254 mm over 86x, which is 3 mm. That makes this a medium-power general setting.

The eyepiece to buy

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Related

Sky-Watcher Classic 250P (10-inch Dobsonian)254 mm f/4.7
Tele Vue 14mm Delos14 mm, 72 deg
Best eyepiece for the Sky-Watcher Classic 250P (10-inch Dobsonian)exit-pupil match

Questions and answers

Tele Vue 14mm Delos in the Sky-Watcher Classic 250P (10-inch Dobsonian): magnification and field?

Good fit. In the Sky-Watcher Classic 250P (10-inch Dobsonian) the Tele Vue 14mm Delos gives 86x with a 0.84 degree true field and a 3 mm exit pupil, inside the telescope's useful range.