Halos, Rainbows, and Other Phenomenon in the First Coast
Hi Nick,I have seen a couple of parhelia recently which have been quite close to the horizon. This got me to thinking whether any halo phenomena would be visible above the horizon after the sun had set. For example, if the sun was one or two degrees below the horizon would it still be possible to see a UTA or CZA? I can't recall any photographs showing such phenomena, how about you? A clear, unobstructed view of the horizon with a partial 22 degree halo, a UTA and a CZA would be quite impressive without the sun's disk in evidence.
I always wondered the same thing, because the sun might set at ground level, but it is still up at the level of cirrus clouds. There was a possible observation of a 'negative subparhelion' on Ice Crystal Halos, http://www.ursa.fi/blogit/ice_crystal_halos/index.php?title=upper_parhelia_over_the_alps&more=1&c=1&tb=1&pb=1#comments
Thanks for that, Nick. Now that you have brought it to my attention, I do actually remember reading that article, but it had completely slipped my mind. The very fact that these seasoned professional observers are discussing the nature of "marginal" phenomenon indicates that the regular, more common halo phenomena are not readily visible after the sun has set. On the contrary, if they were visible, we would be inundated with images. This raises an important question, if they aren't readily visible, why not?
This is one of my recent posts showing a very low right hand parhelion,http://theboltonhalotriangle.blogspot.com/2011/10/22nd-october-2011-right-hand-parhelion.htmlOn this particular day, the sky was very light for quite a time after sunset. I'm sure if anything had developed I would have seen it. Very mysterious.On further thought, the one phenomenon I have seen after the sun has set are upper sun pillars. I'm sure I have seen quite a few images of these after the sun has disappeared below the horizon.
You raise a good point, there are practically no pictures of halos mentioned being seen after sunset. There are not many pictures of halos from a low sun in the first place, I wonder why? I guess from most locations trees litter the horizon, making it hard to tell whent the sun has set and to see some halos.
I've e-mailed Les about this as it is so intriguing. If anyone has an answer, he will! I'll let you know what he says.