def gratingequation(sigma, order, sign, alpha, beta, gamma=0, nd=n_index):
"""Apply the grating equation to determine the wavelength
w = sigma/m cos (gamma) * n_ind *(sin alpha +- sin beta)
returns wavelength in mm
"""
angle = cosd(gamma) * nd() * (sind(alpha) + sign * sind(beta))
return sigma / order * angle
def calc_anamorph(alpha, beta):
"""Calculates the anamorphic magnification
returns the anamorpic magnification
"""
return cosd(alpha) / cosd(beta)
def calc_angdisp(sigma, order, beta, gamma=0):
"""Calculate the angular dispersion according to m/sigma/cos beta
returns angular dispersion in 1/mm
"""
return order / sigma / cosd(beta) / cosd(gamma)