Turning on navigational lights...

[Brian D]

While searching for a replacement steaming light for my boat, I thought I came across a site regarding when to turn on navigational lights. It discussed the three twilights and when navigational lights are turned on. Well, I can't seem to find that site anymore and I've done a search on the subject but came up empty handed. Do we turn on our navigational lights at Civil, Nautical, or Astronomical Twilight? I think it is Nautical, but can't confirm.Thanks.

 

[Bob V]

Civil twilight lights go on

Nautical twilight it is dark enough to take star sightings. In other words lights go on at the earliest twilight when there is still enough light for normal outdoor activities without artificial lights.

 

[Ernie]

and don't forget

In the FOG TOO!!!Another way to think about it is to compare it cars. One hour before sunset until one hour after sunrise.

 

[Anchor Down]

Um…

Definitions for all three terms would actually make this thread understandable. Or do you expect me to bugger off and do my homework, then come back and comment intelligently?

 

[Brian D]

Sorry...

I assumed that the three twilights were understood. My bad.---------- Civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities. Complete darkness, however, ends sometime prior to the beginning of morning civil twilight and begins sometime after the end of evening civil twilight. Nautical twilight is defined to begin in the morning, and to end in the evening, when the center of the sun is geometrically 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct. Astronomical twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the Sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.

 

[Bill Roosa]

I think we are spliting hairs here

In perfect conditions:BMAT to BMCT is 18-6=12 degrees the sun has to move through or 48 minutes of time. In ~20 years of walking around outside in "less than perfect" conditions for the US Army, I have come to the conclusion that I turn my lights on based more on the weather than the position of the sun.It is ~4 amps turn them on early! It's cheap insurance. OBTW don't forget to note it in your ships log. If there is some issue later on the logbook will be the teller of the tale.

 

[abe]

I turn them on when it starts getting dark...

...simple answere from a simple mind.*zzzabe

 

[sailortonyb Allied Mis]

Abe makes sense...

The technical BS here is mind boggling. Turn them on before it gets dark and in inclement weather. It doesnt take a rocket scientist to figure out if you can be seen or not. If you get in a crash, does it really matter what twilight it was....maybe to a lawyer, but you are still just as dead.Sheesh !!!! Tony B

 

[David10790]

Nav rules say

sunset to sunrise and in times of restricted visibility. Nothing to do with twilight that I could find. Any newspaper or almanac will tell you when sunset is at your location. Why get fancy and make life difficult?

 

[Ross]

If you want to know when sunset is stand

outside and look towards the western sky. If you can't find the sun anywhere it has probably set. If it is dark then you should have turned the lights on sooner. I don't need a flash light to read the paper to tell me that the sun is setting.

 

[jleblanc31]

why not all the time

you don't have to worry if it is sunset or sunrise and if a lawyer has to be called in then you are set. some one also mentioned about cars and when he turns the lights on , well most of the newer cars the lites are on all the time. So in conclusion I think I'll just leave them on.

 

[Anchor Down]

Thanks, Brian

That was very informative, but I run things by the seat of my pants, too. Under normal conditions, after sunset, objects begin to lose their sharpness, and when I can begin to see stars, I flip the switch. Of course, under overcast skies, that happens a bit earlier.

 

[Joe]

This is

One for the record books. No offense but this borders on lunacy.Turn the lights on when visibility is reduced either by the setting sun or weather conditions and you should be fine.