distinguishing nav lights from shore lights

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sarabande
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distinguishing nav lights from shore lights

Postby sarabande » Fri Jul 01, 2011 8:55 pm

It seems that nav lights are DC, while other lights ashore are AC.


If, when looking through your binoculars, you make the objective lens describe a small circle, shore lights appear as a series of little dots, and proper nav lights as a continuous line.

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Mark
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Re: distinguishing nav lights from shore lights

Postby Mark » Fri Jul 01, 2011 9:06 pm

sarabande wrote:It seems that nav lights are DC, while other lights ashore are AC.


If, when looking through your binoculars, you make the objective lens describe a small circle, shore lights appear as a series of little dots, and proper nav lights as a continuous line.


Or simply blink exactly 50 times a second and all the shore lights will disappear.

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sarabande
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Re: distinguishing nav lights from shore lights

Postby sarabande » Fri Jul 01, 2011 10:37 pm

or if you are anti-phase they could stay on all the time, and be indistinguishable from DC lights.

But no, if you blink very quickly at 50 Hz, DC lights will go on and off, so a light that is either on or off is a shore light, and a light that is on and off is a nav light.


















I'll stick to Colregs :D

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Arghiro
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Re: distinguishing nav lights from shore lights

Postby Arghiro » Sat Jul 02, 2011 2:39 pm

But lights are either filaments which glow all the time (cos they take longer than 0.02s to cool down) or flourescents which rely on the luminescence of the gas etc in the tube - which will also have better than 0.02s remanence).

I don't believe the OP, where did the idea come from, & have you tested it yourself?

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sarabande
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Re: distinguishing nav lights from shore lights

Postby sarabande » Sat Jul 02, 2011 2:58 pm

yes. I am an empiricist in the tradition of Locke, Berkeley and Hume.

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Telo
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Re: distinguishing nav lights from shore lights

Postby Telo » Sat Jul 02, 2011 9:21 pm

sarabande wrote:yes. I am an empiricist in the tradition of Locke, Berkeley and Hume.


:) :) :)

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DaveS
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Re: distinguishing nav lights from shore lights

Postby DaveS » Sun Jul 03, 2011 4:58 pm

Arghiro wrote:But lights are either filaments which glow all the time (cos they take longer than 0.02s to cool down) or flourescents which rely on the luminescence of the gas etc in the tube - which will also have better than 0.02s remanence).


Fluorescent lights do, in fact, flash (at 100Hz not 50Hz; they conduct on both half cycles). This is why it is potentially quite dangerous to illuminate a rotating machine using a single fluorescent fitting: it acts as a stroboscope. Special twin fittings are available with lag and lead phase shifting circuits to avoid this. If a 3 phase supply is available then supplying 2 standard fluorescents from different phases also works.
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Re: distinguishing nav lights from shore lights

Postby Telo » Sun Jul 03, 2011 9:25 pm

DaveS wrote:
Arghiro wrote:Fluorescent lights do, in fact, flash (at 100Hz not 50Hz; they conduct on both half cycles). This is why it is potentially quite dangerous to illuminate a rotating machine using a single fluorescent fitting: it acts as a stroboscope. Special twin fittings are available with lag and lead phase shifting circuits to avoid this. If a 3 phase supply is available then supplying 2 standard fluorescents from different phases also works.


If you don't have a phase shifter to hand, I'm told that hitting it with a hammer iusually works. Is that right?

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DaveS
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Re: distinguishing nav lights from shore lights

Postby DaveS » Mon Jul 04, 2011 3:59 pm

Shard wrote:
DaveS wrote:
Arghiro wrote:Fluorescent lights do, in fact, flash (at 100Hz not 50Hz; they conduct on both half cycles). This is why it is potentially quite dangerous to illuminate a rotating machine using a single fluorescent fitting: it acts as a stroboscope. Special twin fittings are available with lag and lead phase shifting circuits to avoid this. If a 3 phase supply is available then supplying 2 standard fluorescents from different phases also works.


If you don't have a phase shifter to hand, I'm told that hitting it with a hammer iusually works. Is that right?


It would certainly stop it flashing...
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