% Cross-dispersion definitions:
lam_mid    525[nm]                      Middle wavelength
T_xdp      500[1/mm]                    Cross-dispersion line density
sigma_xdp  1/T_xdp                      Cross-dispersion line spacing
theta_xdp  asin(0.5*lam_mid/sigma_xdp)  Cross-dispersion angle of incidence

% Echelle-dispersion definitions:
theta_B    63.43[deg]                   Echelle blaze angle
dtheta      1.5[deg]                    Echelle in-plane angle
gamma      10.0[deg]                    Echelle out-of-plane angle

% Collimating lens definitions:
R1_doub    183.6850[mm]                 Radius of curvature, surface 1
R2_doub     43.2490[mm]                 Radius of curvature, surface 2
R3_doub    -64.1000[mm]                 Radius of curvature, surface 3
Tc1_doub     1.5[mm]                    Center thickness, element 1
Tc2_doub     3.5[mm]                    Center thickness, element 2
d0_doub     22.5[mm]                    Lens diameter
BFL_doub    97.4495[mm]                 Back focal length