Astrophysics formulas

Hundreds of years ago, the brightness of a star is expressed in “magnitudes” by Astronomers

This system was invented by the Greeks, where the brightest star is the first magnitude while the star with the weakest light is the sixth magnitude

The focal ratio or f/stop is considered as the “speed” of the optics in any telescope or device which uses a lens mechanism

This measurement is computed by dividing the focal length by the lens’ aperture

You have a telescope whose lens aperture is 102 millimeters and focal length of 1000 millimeters