warr: numpy.ndarray
Estimated wavelength for arc
farr: numpy.ndarray
Flux at each arc position
sw_arr: numpy.ndarray
Wavelength of known lines
sf_arr: numpy.ndarray
Flux of known lines
dw: float
Value to search over. The search will be done from -dw to +dw
nw: int
Number of steps in the search
Wavelength after correcting for shift from fiducial values