Odd refraction effect: sunset before sunrise?

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owlice
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Odd refraction effect: sunset before sunrise?

Postby owlice » Sun Jan 08, 2012 4:53 pm

Sunset before Sunrise
Copyright: Sebastian Voltmer
Click to play embedded YouTube video.

From the email submitting this:
Enclosed I send you a link of a very strange refraction effect over a glacier in the french Alps (Mont-Blanc-Massive):

First I pointed the sun with my GOTO mount before the sun appeared over the summit.
I was surprised when I saw a wonderful diamond ring effect at the wrong position; 1° left from the calculated point.
But what's that! The sun was slowly going down and disapeared behind the glacier. A sunset before sunrise?!
I hope to find a correct answer for this effect.

If you have an explanation, please post it. Thank you!
A closed mouth gathers no foot.

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Chris Peterson
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Re: Odd refraction effect: sunset before sunrise?

Postby Chris Peterson » Sun Jan 08, 2012 6:45 pm

owlice wrote:Sunset before Sunrise

From the email submitting this:
Enclosed I send you a link of a very strange refraction effect over a glacier in the french Alps (Mont-Blanc-Massive):

First I pointed the sun with my GOTO mount before the sun appeared over the summit.
I was surprised when I saw a wonderful diamond ring effect at the wrong position; 1° left from the calculated point.
But what's that! The sun was slowly going down and disapeared behind the glacier. A sunset before sunrise?!
I hope to find a correct answer for this effect.

If you have an explanation, please post it. Thank you!

The combination of a glacier and low incidence angle means that reflections will tend to be highly specular. I think what we're seeing to the left of the Sun's position is just a reflection off the ice. As the Sun rises, the angle of incidence changes and the reflected beam moves away from the camera position. The reflection is so bright that the all the surrounding pixels are saturated (that is, what is actually a hair thin zone appears very bloated). As the reflection moves off, the bloat also decreases, which furthers the illusion that something is descending at that location.
Chris

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Chris L Peterson
Cloudbait Observatory
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