Telescope Magnification Calculator

Telescope / Eyepiece Focal Length

mm
mm

Determine Required Eyepiece Focal Length

mm
mm
mm

Maximum Magnification

mm
mm

How to Determine Magnification

To determine the magnification of a telescope, divide the telescope focal length by the eyepiece focal length. It is the formula:

Magnification = Telescope FL / Eyepiece FL

If you already know the magnification capabilities of your telescope, the ability to know what magnification you'll be working with using a given eyepiece is useful information.

Maximum Magnification

The maximum magnification is the highest effective magnification a telescope can provide before it no longer provides any further detail. To calculate this, multiply the telescope aperture by 2.

Max Magnification = Telescope Aperture * 2

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