How far away are ships at night ?

[alec]

In daylight and good vis we can make a fair judgment on how far away a ship might be.

I am not a particularly experienced night sailor but I have always found it difficult to judge the distance of ship's lights at night. Apart from horizon rules etc I would be interested to know of any rules of thumb or methods others use.

Regards,


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[peterb]

We've often tried estimating the distance of a ship, then checking by radar. It's surprising how different they can be. The estimate is usually a lot less than the real distance.

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[johnsomerhausen]

It´s highly dependent on the height of the lights above the water: a supertanker fully loaded will sem farther than when empty
john

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[rickwat]

I admit I'm hopeless. This is my main use for radar but range is only 1 factor I still use a series of compass bearings to determine risk of collision which encompasses(appropriatelly)speed and course in a straightforward way.

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[Johnboy2004]

hi can anyone give me any info on c.a.r.d radar detectors?
where in the uk can i get one , theres very little on the netabout them

cheers

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[Benbow]

<A target="_blank" HREF=http://www.cruisinghome.com/>Cruising home </A> sell the CARD radar detector

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[jimi]

At night I find it virtually impossible in open waters to judge the size of a ship and its distance off from its lights. Like another respondant, I always use radar at night when I need to know the distance.

<hr width=100% size=1>I Have The Body Of A God... Buddha

 

[davehu]

A good question that I would like an answer too as well. All the replies so far are from users of Radar which does not answer the question. Does anyone still sail without radar who can give the answers?? All these recent threads about radar are due I am sure to the recent articles in the PBO etc about fog. IMHO buying radar and thinking you are safe is foolish, to be safe with Radar you must know how to use it, its limitations and how to plot quickly a relative track of another vessel. On small yachts, North up display and electronic compasses and not realistic in terms of cost and power consumption.

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[jimi]

Think the answer is that you can't! Even in known waters with known buoys is difficult sometimes to tell if they are 20 yards or 500yds away. Its sometimes difficult to tell if a ship is a liner 5 miles away or a fishing boat 1 mile away. IMHO the only way you'll get a quick accurate answer to the distance off is using radar.

<hr width=100% size=1>I Have The Body Of A God... Buddha

 

[Mirelle]

non-Radar using answer

The visible range of a ship's white masthead lights is five miles. The visible range of the red and green sidelights is two miles.

So, if you see the white lights but not the sidelights, she is between two and five miles away. If you see the sidelights as well, she is less than two miles away.

Some types of ship will have a blaze of other deck lighting but you should always be able to pick out the masthead lights and the sidelights. The sidelights may not always be where you expect to see them, on the bridge wings. Some containerships, for instance, carry them on the forward breakwater so they are under the forward masthead light.

The one to watch out for with great care is a tug and tow.

<hr width=100% size=1>Que scais-je?

 

[MainlySteam]

Re: non-Radar using answer

<<<The one to watch out for with great care is a tug and tow.>>

To help the point, a while back a yacht sailed between a tug and the coastal barge it was towing off Auckland at dawn - the tug and tow were correctly lit and the yacht was run down by the tow. The yacht's skipper, who was lost, was asleep in his bunk and the crew member who was on watch was not wearing her spectacles even though she apparantly had poor eyesight.

John

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[Evadne]

Re: non-Radar using answer

"Some types of ship will have a blaze of other deck lighting but you should always be able to pick out the masthead lights and the sidelights."

I presume you aren't including fishing boats and X-channel ferries! Especially the sidelights. I agree it is impossible to tell how far off they are purely from the lights, it's often difficult enough in daylight. Sitting in our cockpit the horizon is about 2 miles away, and I reckon that at 2 miles features like windows and people start to become discernable, so if the side windows on a ferry or the deck lights on a fishing boat are visible as tiny but individual dots, I put the range at a couple of miles, or thereabouts. If they are squares or I can make out items on deck it's less than a mile and if I can see faces at the windows, I start to worry. I guess it depends on your eyesight/glasses prescription as well. It's a bit subjective and, has been pointed out, the important thing is the other vessel's course so at night, compass bearings are the most important measurement.


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[jimi]

Re: non-Radar using answer

Re the visible range .. I had thought that the ranges specified were minimum ranges in normal visibility so whilst the sidelights s/b visible at two miles they can is fact be further away or in certain visibility conditions (or obscured by deck light glare) they can be a lot closer when they are perceptable .. ferries are a bugger for that.

<hr width=100% size=1>I Have The Body Of A God... Buddha

 

[ChrisE]

Thanks for the posting

Very interesting.

On a related theme, if like me you are short sighted then you'll find difficulties determining reds and greens in the dark, I beleive that it is something to do with the functions of rods and cones in the eye.

My other half who is long sighted can differentiate the colours alot further off than me.

BTW, like most of the others I rely upon radar when it really matters.

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[MainlySteam]

If you have to look up at their lights then they are very close.

I do not say that in jest having had, despite a very good watch by three crew, an around 250 foot coastal ship materialise off our port bow on a very dark night while passing a port city with car and house lights on high hills behind him but blackness down low.

He had obviously seen us (well /forums/images/icons/crazy.gif) against the blackness to seawards of us and we immediately knew there was no danger (as he was almost beside us going by) - the surprise was that he had got so close unseen, even though he just had his nav lights showing, despite a very diligent watch by us as we had realised the potential for such an encounter.

{Edit: Mirelle's encounter has prompted me that I should have clarified there was no wind, so we were motoring and could not hear others}

John

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by MainlySteam on 23/03/2004 11:20 (server time).</FONT></P>

 

[Mirelle]

Similar story

Running down towards Land's End one fine summer night I head a whispering sound astern and to port of me as I was at the helm and found myself looking UP at the starboard light of a large steam tanker, which was overtaking us to port, having presumably sailed from Milford Haven. Steamers are much quieter at sea than motorships - they are fast becoming rare, of course.

<hr width=100% size=1>Que scais-je?

 

[petery]

Crossing from Littlehampton to Fecamp last autumn at night, the (eperienced ex-naval) helmsman suddenly cried out 's**t theres a huge yacht with a 200' high mast only half a mile away'.

It was Mars (at it's brightest for centuries) hovering above a group of distant fishing boats - but it looked like the port tricolour light over a stern light - so several million miles looked like 1/2 mile!!

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[anchorhandler]

Hmmm bit worrying really....
Does anyone remember the U.S. aircraft carrier (believe in was the Nimitz) calling up the lighthouse keeper and asking what his intentions were?....
Even the most profesional sailors have difficuly judging distances/other vessels/lighthouses?? at nightime.
Simon



<hr width=100% size=1>I'v got 2 ears.2 eyes and 1 mouth....if only i could use them in that proportion!

 

[Peppermint]

Re: To tricky

no reference points just lights. You don't know how high the light is or how bright it is, no horizon or any other clues to judge range, so your guessing.

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