The GREEN FLASH . . .

[Guest]

supposedly seen the moment the sun dips below the horizon. I have never seen it.

Has anyone seen it? Is is more often seen from a boat at sea?

A friend swears he has but he confessed he was looking throught the bottoms of two empty Hieneken bottles.

Cheers

 

[Guest]

..Doug, we gave up looking for it, in the end. I think it's a shaggy dog story, a fig in the imagination (a green fig, naturally) of a handful of beer-crazed yachties. I sat on Shirley Heights, burning my eyeballs out, trying to catch a glimpse. I never blinked or took my eyes off the sun or the horizon and someone, only four feet away shouted "There! Did you see it?!" No, I hadn't seen it, I was sober and I don't believe he had seen anything either, at least not outside his eyeballs! It's a self-perpetuating myth, I think. People don't like to say they haven't seen it, so they lie! Or maybe I've just got useless eyeballs and there's always a green flash but I can't see it. I hadn't thought of that...;-))

 

[Guest]

If you look at the sun constantly long enough (apart from permanently damaging your eyes) and look away you will see a green "blob" apparently its called persistance ov vision. I was hoping that the green flash is not that but some refraction(?) or something ike the last rays going through the water on the horizon and that somebody had seen it. Maybe the mith should be perpetuated.

 

[Guest]

You have missed something. I have seen it twice although six or seven years ago. Once from Daihaie (spelling?) on Guadeloupe and, again from Guadeloupe, at Port St Louis. Never saw it the next time I was in the Caribbean. Too much pollution?

NickB

 

[Guest]

I saw it once, about 30 years ago, in S Devon. It was a distinct flash in the sky just above where the sun had set and a few seconds - might have been 5 or 10, after the sun had set. Incidentally from the position I was, the sun would have set over Rame Head, about 20 miles away, rather than over the sea.

Never seen it since, but often look when I remember. Must have been quite unique met conditions to see it when I did.

I gathered from my Mum it was quite the thing to look out for on Trooper ships in the days when there was an Empire.

 

[Guest]

It\'s Real, Alright

I have seen it in the Indian Ocean and the Red Sea, but if you want a full description there is a page and a half devoted to it in The Marine Observer's Handbook (Met. O. 887). It has also been reported with the Moon and has been frequently seen with the bright planets Jupiter and Venus. A sea horizon is not essential and it has been often seen when the sun sets behind a distant land surface. The green flash is produced by the last rays of sunlight coming from the upper limb at sunset being refracted before reaching the observer's eye.

 

[Guest]

I seem to remember that Eric Hiscock reported seeing it -- but only once. *

.

 

[Guest]

Re: I seem to remember that Eric Hiscock reported seeing it -- but only once. *

It has been reported that Mike sees it after leaving the pub most nights.!!!!! Three of us made a point of looking at the setting sun twice in Bass Strait this week, we didn't see anything. Brian

 

[Guest]

Eric was a teetotaller, I understand.... *

Cheeky b****r, Brian.

 

[Guest]

For you unbelievers, some photographs ...

http://antwrp.gsfc.nasa.gov/apod/ap970909.html

http://mintaka.sdsu.edu/GF/pictures/AAS/greenflash2.jpg

There are various theories for the phenomenon. The most usual is that it is a form of `inferior' mirage -- where the inverted image lies below the erect one. In this mirage, the surface of the Earth, heated by the Sun, produces a layer of hot air of much lower density just at the surface. Grazing light rays bend back up into the denser air above. This phenomenon is the cause of the 'hot-road' mirage, seen above tarmac on a sunny day.

At the transition between the erect and inverted images of the inferior mirage, there is a zone of sky, parallel to the horizon, in which strong vertical stretching occurs. This broadens the Sun's upper green rim, which is normally too narrow to be seen, into a feature wide enough to see easily. It is observable only as the sun is setting at a great distance at a angle below the eye of the observer, so it helps to be on a high vantage point. It needs hot conditions, so is usually seen in the tropics though it is not unknown elsewhere.

I've been looking for years, but never seen it!

 

[Guest]

A most excellent voyage....

A full month on Macquarie Harbour... a bit rushed at the end from Hobart via Babel and Deal to Wport. I shall email both yourself and Brian after I have had a bit of a kip. ( arrived back last Satdee, have since been to Geelong to slip her, arrived back in Hastings 1800 today)

 

[Guest]

Have seen it many times during my days in the Merchant Navy. You need exactly the right conditions. Completely clear sky, very hot and no wind (completely flat and well defined horison), and you need to be a good distance above sea level.

I have only seen it at sea from the highest part of the ship and only in the right conditions.

You will most likely be too low in a yacht, so the likely vantage point will be from the top of a hill looking out to sea, you could try climbing the mast. I guess light pollution and and atmospheric pollution could also be a problem.

 

[Guest]

Hot atmosphere?

The only time I've seen it was just north of Skagen, Denmark. Interestingly, it was the reddest sky I've ever seen, too; the photograph I took just after sunset has an almost totally red sky, with just one tiny patch of blue showing.

 

[Guest]

The latest scientific thinking, alas

holds that what we perceive as the green flash is in fact an optical illusion which is taking place in our own retina; the flash is in fact white, not green, but we see it as green because our eyes have been staring at the sun as it moves ever further into the red spectrum, and are therefore deceieved into thinking that the white refracted image of the sun is in fact green....

 

[Guest]

Re: The latest scientific thinking, alas

I can follow the logic of presistance of vision etc BUT how come there is a flash any way in the first place?

 

[Guest]

It has to do with refraction

You remmeber that you are not meant to wave your sextant at bodies which are close to the horizon, because of odd refraction effects which are greater than the corrections can correct for?

Well, I am not very good at this stuff, and I hope a professional can correct me, but when the sun does go down it has in fact already gone, so to speak. The image you see is a refracted image and it goes red because red light bends the furthest under refraction (remember Newton's prism in your physics lessons).

Now for the bit I cannot remember right. For some reason, in certain climatic conditions, described elsewhere in this thread, a second refracted image, consisting of white light may appear momentarily; this is something like a mirage, and usually hidden by the main image of the sun, but at the instant when the sun sets it is seen alone - as a green image of the sun.

Hope someone can improve on this lame explanation....

 

[Guest]

\'Flash\' is probably misleading..

its just that the very smallest last little teeny-tiny bit of the sun turns green just below it disappears ( its already gone from white to yellow to red). Needs a horizon clear of all cloud, a flat sea ( ie no swell obscuring the true horizon) and best seen through binos ( you only need to look at the very last moment so no danger of frying the retina)

Saw my last one in Bass Strait 7 days ago (Friday evening, Garden Cove to Western Port, flat calm, big high (1024)). Saw my first ( and only) morning one off Tasmania last year, similar conditions, just happened to be looking at a ship to the east thru my binos when the sun rose just astern of her.

 

[Guest]

Hey, welcome back, Frank. How was the cruise? *

?

 

[Guest]

Hey, hang on, Andrew.....

That can't be the whole story, surely, or those photos wouldn't show the green light.

While I suppose one could say cameras have retinas, they've only got recording mechanisms for what they've seen, not interpretive ones.

Maybe it's just that those scientists have photographic vision...?

 

[Guest]

Um, then how come...

you also get a green flash when it is rising?