Given an unrefracted `alt` determine where it will appear in the sky.

def refract(alt_degrees, temperature_C, pressure_mbar):
    """Given an unrefracted `alt` determine where it will appear in the sky."""
    alt = alt_degrees
    while True:
        alt1 = alt
        alt = alt_degrees + refraction(alt, temperature_C, pressure_mbar)
        converged = abs(alt - alt1) <= 3.0e-5
        if converged.all():
            break
    return alt