nominal range of a light signal

[] In signal lighting: The luminous range calculated for dark conditions and with nominal values for the constants in Allard’s law:

1) The visual threshold in point vision in dark conditions is equal to 0.2 microlux or 0.686 nautical mile-candela.

2) Atmospheric transmittance corresponding to a meteorological visibility of ten nautical miles is equal to 0.85 per kilometer or 0.74 per nautical mile-candela.

Note: A nautical mile-candela is the illuminance produced at one nautical mile by a source of one candela.

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