7,500+ items available from stock
Best price guarantee
Your partner for astronomy
Glossary > Telescopes > Optics > Max. useful magnification

Glossary | Telescopes | Optics | Max. useful magnification

The telescope’s magnification should not exceed this factor, because otherwise the image will appear weak and dark.

More magnification equals a better telescope? Beginners often think this, but it is not the determining factor, small or medium levels of magnification are usually more effective. Here you can learn how to calculate magnifications.

A telescope creates a focal point, depending on the curvature of the mirrors or lenses. With the focal length alone, a small level of magnification will be achieved. But in order to be able to look at the image, you additionally need an eyepiece. Imagine an eyepiece as a magnifying glass which enlarges the image at the focal point.

The magnification of a telescope is calculated using the following formula:

Magnification (M) = focal length of the telescope (ft) / focal length of the eyepiece (fe)