Telescope Magnification Calculator
Astronomy & SpaceCalculate your telescope magnification from its focal length and your eyepiece focal length.
Magnification
The magnification power of this telescope and eyepiece combination.
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Creators
Odeh Ahwal0people find this calculator helpful
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Saved
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Astronomy & Space calculators
Frequently Asked Questions
How do I find my telescope focal length?
Focal length is usually printed on the telescope tube or in the specifications, often expressed in millimeters — it is the distance light travels inside the telescope before reaching a focus point.
What is the maximum useful magnification for a telescope?
A common rule of thumb caps useful magnification at about 50 times the telescope aperture in inches, beyond which the image becomes dim and blurry regardless of eyepiece used.
Why does a shorter eyepiece focal length give higher magnification?
Magnification equals telescope focal length divided by eyepiece focal length, so a smaller eyepiece number produces a larger result — shorter eyepieces magnify more but also narrow the field of view.
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