SLTF Marine
LLC. 



Here's
the section from the USCG Navigation Rules (COLREGS), page 142
explaining how to calculate the brightness of a navigation light.
You can use this procedure to see if the LED replacement buls you
bought are bright enough for the application.
8. Intensity of lights (a) The minimum luminous intensity of lights shall be calculated by using the formula: I = 3.43 x 106 x T x D2 x KD
where:
ExampleYour boat, at 38', is less than 12m, which requires an anchor light that's visible for 2 nm. Using the above formula, the result is a light with a brightness of 1.1 candelas. To convert from candelas to lumens, use the formula: Lumens = Candela * 2 * π * (1  cos(θ/2)) (θ in radians) The anchor light is an allaround white light (360° or 2π radians) light. In this situation, the 1.1 candelas is 13.8 lumens. Compare this number to the lumens value on the LED package to see if it is bright enough for your needs. Remember, this method isn't USCG approved, so caveat emptor.


Copyright © 2010 SLTF Marine LLC.  