The brightness function is an empirical relation that determines the distribution of stars by apparent magnitude . Gloss function {\ displaystyle A \ left (m \ right)}
determined from the ratio:
{\ displaystyle dN \ left [m, m + dm \ right] = A (m) dm} ![dN \ left [m, m + dm \ right] = A (m) dm](https://wikimedia.org/api/rest_v1/media/math/render/svg/a52f9892fa90625f2fe4a408792487d86ddeacad)
{\ displaystyle A (m) = {\ frac {dN} {dm}}} 
Where {\ displaystyle dN \ left [m, m + dm \ right]}
- the number of stars with visible magnitudes in a given range {\ displaystyle \ left [m, m + dm \ right]}
, but {\ displaystyle m}
Is the given apparent magnitude .
Integral Gloss Function - Stars {\ displaystyle N \ left (m_ {max} \ right)}
having visible magnitudes not exceeding a given:
{\ displaystyle N (m_ {max}) = \ int _ {- \ infty} ^ {m_ {max}} A (m) dm} 