Telescopes

Magnification and light gathering

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Telescope magnification $M = f_o / f_e$.
• Light gathering $\propto D^2$.
• Big telescopes matter most for collecting light, not for magnification.

Steps

1. Two lenses
2. Turning a small angle into a big one
3. Swap eyepieces
4. Why mirrors?
5. Too much magnification
6. Matching your pupil
7. Light buckets