NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Nav light colors and ranges
From: Trevor Kenchington
Date: 2003 Oct 14, 09:31 -0300
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@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
http://home.istar.ca/~gadus
