A Tele Vue 17.3mm Delos in the Sky-Watcher Skymax 180 gives 156x, a 0.46 degree true field and a 1.2 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 17.3mm Delos in the Sky-Watcher Skymax 180: magnification and field

What the Tele Vue 17.3mm Delos does in the Sky-Watcher Skymax 180, worked from the published focal lengths and apparent field.

Field of view

ring = 0.46 degrees true
dot = 1.2 mm exit pupil

Computed optics

Magnification
156x2700 mm / 17.3 mm
True field
0.46 degrees72 deg / 156x
Exit pupil
1.2 mm180 mm / 156x
Max useful mag
about 360x2x aperture
Barrel match
1.25 in eyepiece in a 2 in focuser
Fits

Good fit. In the Sky-Watcher Skymax 180 the Tele Vue 17.3mm Delos gives 156x with a 0.46 degree true field and a 1.2 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 2700 mm divided by 17.3 mm is 156x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 0.46 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 180 mm over 156x, which is 1.2 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

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Related

Sky-Watcher Skymax 180180 mm f/15
Tele Vue 17.3mm Delos17.3 mm, 72 deg
Best eyepiece for the Sky-Watcher Skymax 180exit-pupil match

Questions and answers

Tele Vue 17.3mm Delos in the Sky-Watcher Skymax 180: magnification and field?

Good fit. In the Sky-Watcher Skymax 180 the Tele Vue 17.3mm Delos gives 156x with a 0.46 degree true field and a 1.2 mm exit pupil, inside the telescope's useful range.