Starship Asterisk*

What a visual sight! Short lived for a second or two, transitioning from the beautiful red sunset to the emerald green sliver at the horizon defined by the Pacific Ocean!

I have visited the ocean several days per year for the last 25 years - hoping to see a green flash everytime. Of those days, I have seen only a handful of sunsets reach the horizon without clouds or haze. Finally, of those, I have seen one where the sun "flares up" seemingly getting brighter as the green, and more eye-sensitive color, evolves. By eye, it seems like the sun is responding to death-throes in the final moments before its imminent disappearance.

Contrary to my initial belief, a constant index of refraction difference between red and green (in constant-temperature air) does not explain the source of the green flash (consistent with the fact they are not seen regularly) . I estimate that the refractive index differential is too low by at least 100x. Instead, an inferior mirage is needed to enhance / amplify this index differential. <<First indications of something unusual are when a sliver of a 'second sun' rises from the horizon as the 'real sun' descends. The lower sun is an inferior mirage (inferior because the image is below the real sun). As the sunset proceeds the lower sun eventually links with the upper sun to form an Etruscan vase or omega shape. The two suns overlap more and more. At the moment when the suns are almost gone the vertical magnification between the different paths of green and red rays is strongest. The green flash then shines forth.>>

I believe the required differential is large enough to restrict the green flash subtended angles to be small, i.e. atmospheric temperature gradients suitable for the green flash are constrained to near the earth's surface, thus naturally limiting the visible green regions to be small slivers.
Clearly, if anyone lives on the ocean, or routinely photographs sunsets, they will likely see several in the course of 25 years, but I'm happy, and feel lucky, to have witnessed one

Thanks for sharing!

I can't be blind as a bat because i can see all of the pictures of the sun, but i can't see any green any where and I'm not color-blind either.

beyond wrote:I can't be blind as a bat because i can see all of the pictures of the sun, but i can't see any green any where and I'm not color-blind either.

Left mouse tap on the image and closely examine
the top of the sun in the picture on the lower left.

neufer wrote:

beyond wrote:I can't be blind as a bat because i can see all of the pictures of the sun, but i can't see any green any where and I'm not color-blind either.

Left mouse tap on the image and closely examine
the top of the sun in the picture on the lower left.

Hey, that sure is a cute little green spot. No wonder i missed it, it's so small. Thanks, your Most Magnificent Quotidian Quotationist

Very Beautiful alter-ego.

is any filter necessary when observing and shooting Green Flash? is it still harmful to look at the sun at such low altitude through a telescope and without filter?

Beautiful, alter-ego. Congrats on bagging your first green flash!

Ann

Amir wrote:Very Beautiful alter-ego.

is any filter necessary when observing and shooting Green Flash? is it still harmful to look at the sun at such low altitude through a telescope and without filter?

Thanks to you, Amir, and others. I'm hoping that the nice comments are based on my comments, and not the pictures. Just in case there's any misunderstanding, the picture seqence I posted is not my own -- I wanted to post the Atmospheric Optics sequence to relay to you how it all "went down". Lacking the psycological factor of the color transition and apparent relative brightness changes, the picture sequence really is an excellent representation of what I saw

Now to your questions.
No, a filter is not necessary. As I've only witnessed one (visual) I'm not an expert in capturing that event, but it is my opinion that a filter is detrimental to the experience. Seeing all the colors, and the transition from red to green is what I really liked. Maybe there is a broadband filter that might help in certain circumstances for technical reasons, e.g color contrast improvement in a photo, but I don't see any advantage to using filters for visual observations. I haven't researched technical details for the existing pictures I've seen so far, so I don't know if there's a secret sauce, if you will.

Second, purely on principle and personal liability reasons, I don't recommend looking at the sun through any optical instrument without a filter. Just before the flash it may be possible to use optical aid up to some aperture limit without a filter for a limited time. I wouldn't be surprised if there is a grey area here, but I'm not going to try to calculate or justify such a range and appropriate conditions. Having worked with lasers and permissable exposure limits for many years, I might try to figure that out for myself, but for you and others my only advice is DON'T FOOL AROUND looking at the sun with optical aid unless you have the appropriate filter
At this moment, I don't know the best filter to use with a telescope, but I'd guess a broadband neutral density filter with as flat as possible transmission over the widest wavelength range would be ideal for best color preservation.

I saw my 1st green flash (I think) back in June of this year. I was shooting the sunset with a Canon 600mm f4 prime lens and got this image.



regards
Kev Lewis
http://www.photosbykev.com

Very nice, Kev! Thanks for sharing your picture. It sure looks like it qualifies as a green flash to me.