Tuesday, July 4, 2017

Photopolarimeter Data for July 3rd

I decided to give the photopolarimeter another test this week, now that we're experiencing summer weather. It's the same instrument I used for February 12th's blog entry http://nearsys.blogspot.com/2017/02/a-modification-to-balloonsat-recording.html?m=1, but modified to see if it could also detect polarization in blue or violet light.

To reach the shorter wavelengths, I taped a second polarizing filter to the first. I was hoping the two filters would act like a single filter with more narrowly spaced lines of polarization. It appears that this did help bring out polarization differences in the blue, but not violet to ultraviolet.

Here are the results for your pleasure. As you'll see, I need to do some more measurements to see if my results from the 3rd are typical.

Sunlight intensity peaked between 3:00 and 4:00 PM for most light wavelengths. And you notice the effects the cloud had between 4:00 and 5:00 PM. However, it appears blue and violet/ultraviolet didn't get the message. They increased in intensity all the way to between 6:30 and 8:00 PM. 
The colors of the sky were brighter in the East-West direction from 12:30 to 4:30 PM and then brighter in the North-South direction from 5:00 to 8:00 PM. But unlike blue, their total intensity's did decrease after 3:30 PM.

The violet/ultraviolet wavelengths were an anomaly. The sky continued to get brighter in this portion of the spectrum until 6:30 PM. The clouds also had a smaller effect on the sky brightness in this region. Odd.

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