Read pertinent information from the image headers,
         especially location and radius of the Sun to calculate the default thematic map
        :return: setes self.date, self.cy, self.cx, and self.sun_radius_pixel

def interpret_header(self):
        """
        Read pertinent information from the image headers,
         especially location and radius of the Sun to calculate the default thematic map
        :return: setes self.date, self.cy, self.cx, and self.sun_radius_pixel
        """
        # handle special cases since date-obs field changed names
        if 'DATE_OBS' in self.header:
            self.date = self.header['DATE_OBS']
        elif 'DATE-OBS' in self.header:
            self.date = self.header['DATE-OBS']
        else:
            raise Exception("Image does not have a DATE_OBS or DATE-OBS field")

        self.cy, self.cx = self.header['CRPIX1'], self.header['CRPIX2']
        sun_radius_angular = sun.solar_semidiameter_angular_size(t=time.parse_time(self.date)).arcsec
        arcsec_per_pixel = self.header['CDELT1']
        self.sun_radius_pixel = (sun_radius_angular / arcsec_per_pixel)