Green flash

C

ChrisE

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www.simpleisgood.com
After watching the sunset for the last ten years in all the right places like the trade winds crossing, the Caribbean and all sorts of other hot places, I finally saw one in the North Sea, the last limb of the sun was distinctly green. It lasted about two seconds and was viewed about 30 miles off looking towards Cromer on a clear stillish evening.

I reckon that some smart person in a RIB could sell a trip like that every clear still evening on the East Coast. Doh, that would be about once a decade then!
 
most unusual near land ..... as you are aware it needs fairly still relativly cool clean air upsun of the observer, so presumably it is even more rare off cromer

interesting phenomina though isnt it
 
The green appearance of the last sliver of the sun itself is just an after image that you can re-create any time you like by looking at the sun for a few seconds then shutting your eyes.

Those who claim to have seen the legendary green flash say the whole scene turns green for a split second. I'll believe it when I see it though I'm not averse to watching for it - with a rum punch in hand.
 
the green flash is in fact the result of the suns visible spectrum being bent by refraction by the earths atmoshpere after it has dipped below the horizon. it is a well known phenomina, and to poor scorn on it just because you havnt seen it does you less justice to yourself than you may think

if you look at the sun for a few seconds to re-create this green flash I suggest you will not be seeing anything soon ...... it is a stupid thing to do let alone suggest it is done ......

it is a fairly common phenomna and often seen when conditions appear 'right' ....... in fact when on the bridge at sundown I normally look for it out of curiosity, sometimes its there sometimes its not.
 
I wasn'r aware of the atmospheric conditions that caused it and thanks for the info. On the same evening on western horizon we saw a rainbow effect on the clouds once the sun was below the hoizon but still high enough to illuimnate the clouds. It was all going so well until the NW6 kicked in!
 
Saw it once off Gibraltar at dawn - I had thought it was only a sunset phenomenum - and like an idiot I shouted to everyone down below to come up and see, of course it had gone by the time they arrived ...............
 
in theory - if the conditions are right, dawn and dusk, but as you must be looking in the right spot it is more commonly observed at sunset.
 
[ QUOTE ]
Those who claim to have seen the legendary green flash say the whole scene turns green for a split second. I'll believe it when I see it though I'm not averse to watching for it - with a rum punch in hand.

[/ QUOTE ]
I've seen it 3 times; once in the north sea and twice off Bombay. The first time I didn't believe what I'd just seen (or thought I'd seen) - the sun about to dip down over the horizon and then a green flash for an instant and then all back to normal.

Keep looking and one day.........
 
Hi Chris

I have seen it twice, once as an 8 year old mackerel fishing on a Newquay tripper boat where the skipper told everyone to look as it might happen, the other between Dartmouth and Ushant a couple of years back. So I count as a believer!

The other strange one, also seen in the western Channel was a nightime rainbow created from bright moonlight - a moonbow?

Robin
 
Cromer, eh?! did have a cromer crab supper one evening and never felt so ill. hallucenogenic it was and saw lots of green .... don't need a rib either ... !

how were the trolls, where'd you leave the boat?
 
And the key-hole ....

Where the suns lower limb extends down to the horizon during setting giving the apparent look of a flattened keyhole ....

Many a time on bridge looking for green flash or keyhole ....
 
Undoubtedly there is a phenomenon seen by some people. Whether it is an artefact (i.e. optical illusion) or a real physical event is, as far as I know, unproven. I have seen the green in the sun's upper limb which I was able to prove to my own satisfaction was an illusion.

I have seen no explanation credible to a physicist for it, nor have I seen it for myself and until such time I will remain open-minded but sceptical.

As to looking at the sun, we all do it every day (well, not in Britain perhaps) but I would have thought it a fair assumption that readers of this site would have the intelligence not to stare at it till they go blind. In my book that ranks alongside 'Peanuts - warning, may contain nuts' or 'do not put your dog in this microwave' so I think we can do without the aggressive rudeness, thank you.
 
no agressive rudeness intended - if is was taken as that then it was out of order I agree .... it is and was a statement that staring into the sun is stupid (aka unintelligent), even for 'a few seconds', as the damage caused is accumalative.

please rest assured I did not accuse you as being stupid - I dont even know you

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I have also seen the effect in the Grenadines.
I found this explanation which seemed reasonable :-


The green flash.

As light from the sun passes through the atmosphere, it is refracted. Since the amount of bending is slightly different for each color, separate images of the sun are formed in each color of the spectrum. The effect is similar to that of imperfect color printing in which the various colors are slightly out of register. However, the difference is so slight that the effect is not usually noticeable. At the horizon, where refraction is maximum, the greatest difference which occurs between violet at one end of the spectrum and red at the other, is about 10 seconds of arc. At latitudes of the United States, about 0.7 second of time is needed for the sun to change altitude by this amount when it is near the horizon. The red image, being bent least by refraction, is first to set and last to rise. The shorter wave blue and violet colors are scattered most by the atmosphere, giving it its characteristic blue color. Thus, as the sun sets, the green image may be the last of the colored images to drop out of sight. If the red, orange, and yellow images are below the horizon, and the blue and violet light is scattered and absorbed, the upper rim of the green image is the only part seen, and the sun appears green. This is the green flash. The shade of green varies, and occasionally the blue image is seen, either separately or following the green flash (at sunset). On rare occasions the violet image is also seen. These colors may also be seen at sunrise, but in reverse order. They are occasionally seen when the sun disappears behind a cloud or other obstruction.

"The phenomenon is not observed at each sunrise or sunset, but under suitable conditions is far more common than generally supposed. Conditions favorable to observation of the green flash are a sharp horizon, clear atmosphere, a temperature inversion, and an attentive observer. Since these conditions are more frequently met when the horizon is formed by the sea than by land, the phenomenon is more common at sea. With a sharp sea horizon and clear atmosphere, an attentive observer may see the green flash at as many as 50 percent of sunsets and sunrises, although a telescope may be needed for some of the observations.

"Duration of the green flash (including the time of blue and violet flashes) of as long as 10 seconds has been reported, but such length is rare. Usually it lasts for a period of about 1/2 second to 2 1/2 seconds with about 1 1/4 seconds being average. This variability is probably due primarily to changes in the index of refraction of the air near the horizon.

"Under favorable conditions, a momentary green flash has been observed at the setting of Venus and Jupiter. A telescope improves the chances of seeing such a flash from a planet, but is not a necessity."

Dave.
 
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