All signs constructed or erected hereunder shall have a maximum luminance level of 4,000 nits during daylight hours, and, if illuminated at night, must have a maximum luminance level at 750 nits, regardless of the method of illumination, at least 1/2 hour before apparent sunset, as determined by the National Oceanic and Atmospheric Administration (NOAA) and throughout the night, if the sign is energized, until apparent sunrise, as determined by the NOAA.