A Tele Vue 3.5mm Delos in the Celestron StarSense Explorer DX 102AZ gives 189x, a 0.38 degree true field and a 0.5 mm exit pupil. The worked calculation and whether it sits in the useful range.

Updated 05 September 2026.

Eyepiece and telescope pairing

Tele Vue 3.5mm Delos in the Celestron StarSense Explorer DX 102AZ: magnification and field

What the Tele Vue 3.5mm Delos does in the Celestron StarSense Explorer DX 102AZ, worked from the published focal lengths and apparent field.

Field of view

ring = 0.38 degrees true
dot = 0.5 mm exit pupil

Computed optics

Magnification
189x660 mm / 3.5 mm
True field
0.38 degrees72 deg / 189x
Exit pupil
0.5 mm102 mm / 189x
Max useful mag
241xpublished
Barrel match
1.25 in eyepiece in a 1.25 in focuser
Fits

Good fit. In the Celestron StarSense Explorer DX 102AZ the Tele Vue 3.5mm Delos gives 189x with a 0.38 degree true field and a 0.5 mm exit pupil, inside the telescope's useful range.

Magnification is the telescope focal length divided by the eyepiece focal length: 660 mm divided by 3.5 mm is 189x. The true field of view is the eyepiece's 72 degree apparent field divided by that magnification, 0.38 degrees.

The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 102 mm over 189x, which is 0.5 mm. That makes this a high-power lunar, planetary and double-star setting.

The eyepiece to buy

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Related

Celestron StarSense Explorer DX 102AZ102 mm f/6.5
Tele Vue 3.5mm Delos3.5 mm, 72 deg
Best eyepiece for the Celestron StarSense Explorer DX 102AZexit-pupil match

Questions and answers

Tele Vue 3.5mm Delos in the Celestron StarSense Explorer DX 102AZ: magnification and field?

Good fit. In the Celestron StarSense Explorer DX 102AZ the Tele Vue 3.5mm Delos gives 189x with a 0.38 degree true field and a 0.5 mm exit pupil, inside the telescope's useful range.