Shop Magazine
%SALE%
EN / $
✓ Europe's largest sport optics specialist
✓ 7,500+ items available from stock
✓ Personal advice & service
🎄 Right of return up to 31.01.2025
Get closer
Binoculars Spotting scopes Digiscoping Night vision Rangefinders Riflescopes Tripods Outdoor Microscopes % SALE %
Glossary > Telescopes > Optics > Aperture ratio

Glossary | Telescopes | Optics | Aperture ratio

Is the ratio of the aperture to the focal length of a telescope.

The focal ratio

The focal ratio of a telescope is the relationship between the telescope aperture and the focal length. A telescope with a 100 mm aperture and a focal length of 1000 mm has a focal ratio of f/10. The focal length is 10 times greater than the aperture.