Vision by the normal eye when adapted to levels of luminance of at least several candelas per square metre.
Note: The cone receptors of the retina are considered to be the principal active elements under these conditions, and the spectrum appears coloured.
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