A Celestron X-Cel LX 25mm in the Sky-Watcher Flextube 300P (12-inch Dobsonian) gives 60x, a 1 degree true field and a 5.1 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Celestron X-Cel LX 25mm in the Sky-Watcher Flextube 300P (12-inch Dobsonian): magnification and field

What the Celestron X-Cel LX 25mm does in the Sky-Watcher Flextube 300P (12-inch Dobsonian), worked from the published focal lengths and apparent field.

Field of view

ring = 1 degrees true
dot = 5.1 mm exit pupil

Computed optics

Magnification
60x1500 mm / 25 mm
True field
1 degrees60 deg / 60x
Exit pupil
5.1 mm305 mm / 60x
Max useful mag
about 610x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Flextube 300P (12-inch Dobsonian) the Celestron X-Cel LX 25mm gives 60x with a 1 degree true field and a 5.1 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 1500 mm divided by 25 mm is 60x. The true field of view is the eyepiece's 60 degree apparent field divided by that magnification, 1 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 305 mm over 60x, which is 5.1 mm. That makes this a low-power, wide-field and deep-sky setting.

The eyepiece to buy

Shop Celestron X-Cel LX 25mm on AmazonaffiliateFind Celestron X-Cel LX 25mm on eBayaffiliate

Related

Sky-Watcher Flextube 300P (12-inch Dobsonian)305 mm f/4.9
Celestron X-Cel LX 25mm25 mm, 60 deg
Best eyepiece for the Sky-Watcher Flextube 300P (12-inch Dobsonian)exit-pupil match

Questions and answers

Celestron X-Cel LX 25mm in the Sky-Watcher Flextube 300P (12-inch Dobsonian): magnification and field?

Good fit. In the Sky-Watcher Flextube 300P (12-inch Dobsonian) the Celestron X-Cel LX 25mm gives 60x with a 1 degree true field and a 5.1 mm exit pupil, inside the telescope's useful range.