[Public-List] USCG Alert re sailboat nav lights' vertical angle

[mahseer at kos.net]

The incandescent filament is a point source of light that emits in all directions and the half sphere focus,s the light rays back to the filament thus increasing the light level that is emitted out. There may also be horizontal rings above and below the centre dome lens these also focus the light back to the centre filament. Good assembly’s will also have at the back of the housing a metal reflector behind the bulb to again helping light output. 
John Boor

Sent from my iPad

> On Apr 7, 2019, at 10:27 AM, Michael Connolly via Public-List <public-list at lists.alberg30.org> wrote:
> 
> George and John,
> I don't know the beam angle of the LED. There is only one LED flat square pad on this replacement lamp. I assume that the light just comes straight off the LED pad. The glass lenses I have are dome shaped and are about 1-1/4" half sphere. The bronze housing covers most of the lens except at the leading edge. I assumed that the light emitted from the source, either LED or incandescent illuminates the entire inside of the half sphere lens and then exits only where permitted by the opening in the bronze housing. In my understanding the entire glass globe glows with light. There is no attempt of the glass to focus the emitted illumination. Whatever escapes through the bronze housing is available to be broadcast. I assume the distance that it can be seen is based on the candle power of the illumination source.