Question

Compute the magnitude of the faintest object observed with a 1 m optical telescope.

Answer 1

Solution. More light enters the telescope, the fainter objects can be viewed. Limiting magnitude of a telescope can be found according the following formula: 

$$M_L=2.5^m+5\times lg D$$

where D is diameter of the main lens or mirror of the telescope in millimeters. Therefore

$$M_L=2.5^m+5\times lg 1000=17.5^m$$

Answer.

$$17.5^m$$