XD20170319 click observed using the long blue camera and the 111 l/mm grating. All throughput measurements are based on observations of spectrophotometric standards, collected under photometric conditions. Throughputs are defined as follows:

where: N_d(λ) is the number of photons detected with wavelength λ and N_t(λ) is the number of photons of the same wavelength hitting the telescope's primary mirror. The latter is given by:

where N_*(λ) is the star's photon flux at wavelength λ above Earth's atmosphere, in number of photons/cm²/s, μ is the airmass, and A_λ is a mean monochromatic extinction coefficient.

The numbers available below are average values, that do not account for throughput variations as a function of grating angle.