Measured +1 and −1 order efficiencies vs wavelength of a 2400 /mm multilayer-coated grating operating at angles of incidence of 10В°. The solid curves are the reflectances of the multilayer coating with 30 Mo/Si periods for the indicated angles of incidence, shifted to account for the different angles of deviation for the +1 and −1 orders. The reflectance values were reduced by factors of 0.32 and 0.34 which represent the groove efficiencies in +1 and −1 orders.