The Half-Astrophysicist Blog

The Green Flash Podcast

Welcome, 365 Days of Astronomy listeners.  As promised, I am posting some of my pics of green flashes and green flash related materials.

First, I talked about how the Earth’s atmosphere acts like a prism as sunlight passes through it.  The effect gets more pronounced near sunset and you can see (with magnification) a bit of blue and green on the upper rim (right in this image) of the Sun and reds and oranges on the lower rim (left in this image) of the Sun.  I have been fortunate enough to watch sunset with the McMath-Pierce Solar Telescope on Kitt Peak several times.  It projects a large image (about 80cm in diameter) on a table.  Here is what the effect looks like (click to embiggen).

Now here is what I was mentioning when you see a bit of the Sun that looks like it is about to get pinched off.  When you see this, you can almost be assured a mock mirage flash is coming.I have several green flash pictures.  The best of the bunch are from a cruise in December of 2009.  Here are a couple of mock mirage flashes.  Note there are two in progress in the last of the series of images.  You can get several mock mirage flashes in one sunset.

Green flashes can occur well before sunset.  The brightest one I ever saw was at Kitt Peak when I took my father to the Nightly Observing Program.  Part of the program is watching sunset.  They get you over there a few minutes beforehand of course so you don’t miss it.  The guide was talking about sunset when all of a sudden there was an amazing green flash.  You may have seen a person use a green laser pointer.  Well, that’s about what it looked like.  A green laser pointer dot on the limb of the Sun.  Since this was several minutes before sunset, most people were listening instead of watching.  I almost didn’t believe what I saw except that there were about half a dozen others that were ooohing, aaahing, and wondering what the heck that was.

Here is an image of an early green flash…taken from the cruise.  Note the piece breaking off at the top of the Sun.  I wasn’t trying to capture a green flash here…I was just taking test shots, checking exposure times and zoom settings and got lucky. Some people have suggested giving this a name such as a green segment, although I believe this is a mock mirage flash.

Just to show you that you can see a green flash away from the ocean, here is one I took from Windy Point on the Catalina Highway near Tucson in February of 2010.  Look closely and you can see the flash is cut into two pieces by the mountain peak.

Andrew Young at San Diego State has a great green flash page where you can find much more in depth explanations.

I hope you have enjoyed this little tour of green flashes.  There are lots of images out there of them.  Go out and try and see them yourself.  Post any observations or pics.  I would love to hear about them!

April 27, 2010 - Posted by | Astronomy, Astrophotography, Observing, Uncategorized

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