Sunday, July 1, 2012

Solar Halo

June 23, 2012.  The Wabash is calm and very low.  I looked over the side of the pedestrian bridge and saw a strange arc in the water.  Then I realized it was a reflection of the sky.  I looked up overhead and sure enough saw that the sun was surrounded by a halo.

Link to solar halo: 

Link to solar halo:

Just so happened that the edge of the halo was at zenith when I took the picture.  This is evident because you can see the reflection of the observer/photographer (me), at nadir.

Link to zenith:

Link to nadir:

The sun is never at zenith because Lafayette is north of the Tropic of Cancer.  The halo is at an angle of 22 degrees from the sun.  How many days in the year is it possible for the edge of a solar halo to be at zenith?  What months are they?

Notice not only the reflection, but the shadow of the bridge and the observer is evident.  From the information given, can you calculate the height of the bridge?  Can you estimate the time of day?


Another view of the solar halo a few minutes later, from a point in downtown Lafayette.  Inside the arc the sky is grey and outside it is blue.  Why is this?

These pictures were taken June 23, 2012.

Link to Wabash River levels:

Link to another scene from the bridge on a different day:

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