(a) The minimum luminous intensity of lights shall be calculated by using the formula:
I = 3.43 × 106 × T × D2 × K−D
Where:
I is luminous intensity in candelas under service conditions,
T is threshold factor 2 × 10−7lux,
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 the following table (Table 84.14(b)):
Table 84.14(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 |