CFR > Title 33 - Navigation and Navigable Waters > CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY > SUBCHAPTER E—INLAND NAVIGATION RULES (parts 83 to 90) > PART 84—ANNEX I: POSITIONING AND TECHNICAL DETAILS OF LIGHTS AND SHAPES > 84.15—Intensity of lights.

84.15—Intensity of lights.

(a) The minimum luminous intensity of lights shall be calculated by using the formula:

Code of Federal Regulations

I=3.43×106×T×D2×K−D
where I is luminous intensity in candelas under service conditions,
T is threshold factor 2×10−7 lux,
D is range of visibility (luminous range) of the light in nautical miles,
K is atmospheric transmissivity. For prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.
(b) A selection of figures derived from the formula is given in Table 84.15(b):
Table 84.15(b)
Range of visibility (luminous range) of light in nautical miles D Minimum luminous intensity of light in candelas for K=0.8 I
1 0.9
2 4.3
3 12
4 27
5 52
6 94