How do you adjust stellar magnitudes to account for elevation?

I know the atmospheric extinction from 1 airmass of clean air is 0.33 magnitude. I already know how to convert elevation to airmasses.





How do I get the magnitude correction to add from the number of airmasses?
How do you adjust stellar magnitudes to account for elevation?
You have to remember that both extinction and magnitudes work in logarithmic scale; therefore loss of magnitudes is simply proportional with the number of air masses:


I = I_0 * 10^(-n k), wiht k the extinction due to one air mass;


delta_m = 2.5 lg(I/I_0)





For n=1, you get the magnitude loss for one air mass; you can figure the rest.
Reply:Elevation is adjusted out.