I think there might be a mistake in the AM formula for the shadow stick.
sqrt(1+(h/s)^2) is what I derived
Estimo que tu error esta en haber considerado el angulo de altitud solar no el de cenit. La expresion utilizada en el texto esta correcta.
Our team is going to publish a Chapter in book namely, "Borate Phosphors Processing to Application" in CRC Press, Taylor & Francis Group, LLC.
In this book of chapter 8, I am going to use a Air mass ratio above figure from this site"
So please kindly convey your permission or NOC for the same.
I stumbled upon this page when trying to figure out sunset on planets other than Earth. Unfortunately, your formula is assuming no curvature of the planet. Put in an angle of 90 and nothing comes through--but that's not what we see when we watch a sunset.
Nice to mention: I believe that the first equation, which is only valid for small angles, is usually referred to as the "plane parallel approximation".
Pedantically speaking this is not correct: "the air mass is not quite equal to the atmospheric path length when the sun is close to the horizon." I believe that airmass always = the atmospheric path. But, the plane parallel approximation for airmass deviates from the exact solution significantly at angles close to 90 (more than 3% error for theta > 80).