Nitpicker wrote:<animated gif>
Animated gif of the sunset on Jan 5 from my backyard in Brisbane, seen through smoky bushfire haze.
Great work. I'd love to do something like that. Is the reddened tree shadow the most distant of three trees between the camera and the sun? The red effect is unexpected.
Thanks Mike. The gum tree in the foreground is less than 100m from the camera. The gum trees on the ridgeline behind which the Sun sets, are about 1km away. The reddening of the tips of these more distant trees, is merely the effect of some of the sunlight passing through the thinner parts of the foliage.
The shots were taken with no filters whatsoever (apart from the smoke, but even that may not have been necessary, it just made it easier for the exposures to capture both the sunspots and the trees) with the sun about 6° above horizontal.
Chris Peterson wrote:I'm not sure it could be called a flash. Any image of the Sun near the horizon (or stars, for that matter) will show the effects of dispersion, with a red fringe at the bottom and a blue fringe at the top. That effect is stable, lasting for many minutes.
I'd say I've never noticed a green flash since I've lived most of my life on the east coast of a continent, or nowhere near the ocean. Green flashes seem most common over the ocean. I've only ever actively observed a handful of sunsets over the ocean in other parts of the world, and (prone to a nice sleep in) only a handful of sunrises anywhere.
Prismatic dispersion of light does make more sense in this APOD (thanks Chris). I've never noticed it in any of my sunset or sunrise shots, but that's not that many. However, every single crepuscular colour shot of Mercury and Venus I've ever taken, shows it to some extent. And I can often see it if I bother to observe stars low on the horizon, too. Initially I thought this was an aberration in my optics, but it is really an aberration of the sky (which some people seem to like). Anyway, it just made me revisit the theory on this topic, which immediately confused me, as my initial reckoning put red on the top and blue on the bottom. It was not until I read the last section -- "A Seeming Discrepancy Explained" -- in the following link, that it suddenly made sense:
http://www.astropix.com/HTML/L_STORY/At ... ersion.HTM