Vision by the normal eye when adapted to levels of luminance below some hundredths of a candela per square metre.
Note: The rod receptors in the retina are considered to be the principal active elements under these conditions. The spectrum appears uncoloured and the maximum luminous efficiency is shifted to a shorter wavelength than in photopic vision.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM