The Half-Astrophysicist Blog

The Omega Sunset

I have been a little behind and negligent posting recently.  I will try to get back on a more regular schedule here.

First thing I want to share was taken in late September when I was in Florida.  I got some nice pictures of sunset.  Here is the first one.

Look closely at the horizon.  You see a little bit of orange beneath the Sun. Here is the next picture.

As you can see, that bit of orange has risen up to meet the setting Sun.  This phenomena is called an inferior mirage (those little spiky things are trees from Egmont Key.  They are also distorted by Earth’s atmosphere).  What you are seeing is a mirage of the Sun.  The warm water bends the Sunlight as it comes toward you resulting in a second inverted image of the Sun beneath the setting Sun.  As the Sun sets, the mirage moves upward and they meet.  The resulting shape looks like the Greek letter omega and this phenomena is sometimes called an omega sunset.  The physical process is the same as the one that gives the “wet road” illusion on a hot summer day.  In this case the mirage is due to the warm waters of the Gulf of Mexico.

Frequently these sunsets are accompanied by a green flash (called, not surprisingly, an inferior mirage flash).  I did not get a green flash on this trip, probably due to a somewhat hazy atmosphere scattering the green light (shorter wavelength light is scatter more than longer wavelength light).

Unfortunately, my camera died on this trip…the shutter went bad and then when I got it back the power board went (they are fixing that for free) but the upshot is, I have been without my camera for a while and I am getting antsy to get it back and start shooting again!


November 11, 2010 - Posted by | Astrophotography, Atmospheric Physics, Optics, Photography


  1. Lovely!

    Comment by livvy30 | November 11, 2010 | Reply

  2. Yes, when the air is clear enough, you get a green flash after an Omega sunset – I’ve experienced that several times, e.g. last year from Tenerife: has the whole sequence. It worked again this year in Sicily.

    Comment by skyweek | November 12, 2010 | Reply

  3. Yep, you got the green flash. If you type green flash into the search box on my blog, you will see pics of several green flashes (including sunsets with multiple green flashes, mock mirage flashes, and a rare cloudtop green flash). I like chasing green flashes. Fortunately, they occur more frequently and under a wider variety of conditions than most people think.

    Comment by halfastro | November 12, 2010 | Reply

  4. Once I originally commented I clicked the -Notify me when new feedback are added- checkbox and now every time a comment is added I get 4 emails with the identical comment. Is there any approach you may take away me from that service? Thanks!

    Comment by Blackjack | February 10, 2011 | Reply

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