  We present the analysis of four hours of spectroscopic observations of NGC
6946 with the SITELLE Imaging Fourier Transform Spectrometer on the
Canada-France-Hawaii Telescope, acquired to search for supernova light echoes
from its ten modern supernovae. We develop a novel spectroscopic search method:
identifying negatively sloped continua in the narrow-band SN3 filter as
candidate highly-broadened P-Cygni profiles in the H$\alpha$ line, which would
be characteristic of the spectra of supernovae ejecta. We test our methodology
by looking for light echoes from any of the ten supernovae observed in NGC 6946
in the past 100 years. We find no evidence of light echoes above the survey
surface brightness limit of 1$\times$10$^{-15}$erg/s/cm$^2$/arcsec$^2$.
