Optics & gearDefinedTerm
Aperture
The clear diameter of a telescope's main optical element.
The single most important spec — it sets light-gathering and resolution.
Used in these guides
- Refractor vs. Reflector vs. Catadioptric: Optics, Honestly ComparedOptics & gear
- Your First Telescope: Why Aperture Beats MagnificationOptics & gear
- Eyepieces and Focal Ratio: The Math That Sets Your ViewOptics & gear
- Astrophotography with What You Have: Phone and TripodImaging the sky
- Tracking the Sky: Why Equatorial Mounts ExistImaging the sky
- Stacking: How Amateurs Beat Light Pollution with MathImaging the sky
- Galileo's Telescope: Four Moons That Changed EverythingHow we learned where we are