Various embodiments of the present disclosure include a C-arm registration system employing a controller (70) for registering a C-arm (60) to a X-ray ring marker (20). The X-ray ring marker (20) includes a coaxial construction of a chirp ring (40) and a centric ring (50) on an annular base (30). In operation, the controller (70) acquires a baseline X-ray image illustrative of the X-ray ring marker (20) within a baseline X-ray projection by the C-arm (60) at a baseline imaging pose, derives baseline position parameters of the X-ray ring marker (20) within the baseline X-ray projection as a function of an illustration of the centric ring (50) within the baseline X-ray image, and derives a baseline twist parameter of the X-ray ring marker (20) within the baseline X-ray projection as a function of the baseline position parameters and of an illustration of the chirp ring (40) within the baseline X-ray image.