  Spectrograph is an optical device that is used to disperse photons of
different energies $E$ into distinct directions and space locations, and to
take a snapshot of the whole spectrum of photon energies with a spatially
sensitive photon detector. Substantial advantage of a spectrograph over an
ordinary spectral analyzer, is its ability to deal with many photon energies
simultaneously, thus reducing exposure time per spectrum considerably. To
realize a spectrograph, dispersing elements with large angular dispersion rate
are required. Here we show, on the example of CDW x-ray optics [1-3], that
multi-crystal arrangements may feature cumulative angular dispersion rates more
than an order of magnitude larger than those attainable in single Bragg
reflections. This makes, first, hard x-ray spectrographs feasible, and,
secondly, a resolving power beyond $E/\Delta E \gtrsim 10^{8}$ achievable.
