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