Earthshine blog

Torben took these pictures at MLO:

Click here.

I have improved the plot showing the periodic bias level for multiple areas on the CCD. I have added arbitrary offsets to separate the different datasets from each other, and I have included a small figure showing the location of the five 16×16 areas on the CCD.

Our telescope is in the Groundwinds building:

This is Ahmad and Rodrigo’s report on the spectral properties of the telescope:

I looked at a bright white LED instead of a bright green laser.

Imaged it with the Canon 35 mm camera as before.

The result is exactly the same scattered light power law around the source.

Did this to check that nothing funky is going on with using a laser as a point source!

I added a scattering plane to the setup – a translucent tupperware lid was placed directly in front of the camera lens. Imaged the LED with and without the scattering plane. The lid scattered light very nicely (left) versus naked LED (right)!

The red curve shows the scattered light profile, the black curve the naked LED. Light is scattered on all scales in this experiment. Can one have a regime where scattering in the optics is dominant and elsewhere where atmospheric scattering is dominant? Not sure at all about this — my feeling is if the atmospheric scattering has a shallower power law index than the optics scattering, then it will always win. Could scattering be scale dependent?

The power law index for the naked LED is -2.6, for the scattered version it’s -1.5. This latter value is very similar to what we get for the moon in the 35 mm camera shooting through air! The tupperware lid simulates the Earth’s atmosphere, presumably by accident.

Scattering through camera optics, air and tupperware lids all produce power law profiles. Is that not interesting? Scattered light follows a power law under a wide range of conditions!