Answer to Question #88780 in Optics for Navdha

Question

Calculate the magnitude of the faintest object that can be detected by an optical
telescope of diameter 5.0 m.

Answer 1

For this problem we can use formula

$$m=2+5lg(D)$$

D - diameter telescope in millimeters; m - magnitude

Calculating

$$m=2+5lg(5000)=20.5$$