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    Re: Nav light colors and ranges
    From: Trevor Kenchington
    Date: 2003 Oct 14, 09:31 -0300

    Paul Werner wrote:
    > I think it is like this:
    > BOAT 7-12 m, UNDER SAIL
    > (M = visibility range nautical mile
    > cd = luminous intensity candela)
    > Either (1):
    > Green sidelight 1M 0,9cd + red sidelight 1M 0,9cd + sternlight 2M 4,3cd
    > Or (2):
    > Bicolourlight green/red sidelight 1M 0,9cd + sternlight 2M 4,3cd
    > Or (3):
    > Tricolourlight green/red/white at top of mast 2M 4,3cd [snip]
    That assumes that the ColRegs standards are based on the power of the
    bulb and suppose that there is no reflector behind it. I would expect
    that the standards are actually written in terms of the light emitted,
    which has two effects. Firstly, a green sidelight with a reflector
    behind the bulb (such that the 360-degree emission of light from the
    filament leaves the light as a 112.5-degree beam) will not need as
    powerful a bulb as a bicolour or tricolour light that emits over 225 or
    360 degrees. Secondly, a standard based on emitted light means that a
    coloured light needs a more powerful bulb than a white light does, for
    the same number of candelas.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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