F) from the change in sky brightness (M, in mag/arcsec2). We measured the original flux to be
298.6 counts at M=20.7 mag/arcsec2, so we used the equationLight Pollution
The original picture was altered using a program called IRAF (Image Reduction and Analysis Facility). In order to change the
picture to show the different sky brightness, I had
to find the change in the flux (F) from the change in sky brightness (M, in mag/arcsec2). We measured the original flux to be
298.6 counts at M=20.7 mag/arcsec2, so we used the equation
FB = FA * 10( M / 2.5)
Where FB equals the new flux, FA equals the original flux of 298.6 counts,
and M equals the change mag/arcsec2. As an example, here is
how you would find out FB for the first site, Mt. Wilson:
M = 20.7 - 19.8 = 0.9 mag/arcsec2
FB = 298.6 * 10(0.9 / 2.5) = 684.1 counts.
Then you would subtract 298.6 from 684.1 to find F, which would
be 385.5 counts. What happens to this number?
I added this number to the original flux to create the image of what it would look like from Mt. Wilson. This new flux is the amount of noise that hinders our ability to see the night sky. So, if there are more counts, it is harder to see the night sky.
I also used that program to alter the pictures a little to make the transitions between sites a little easier to see, so I made the background sky darker. In the "real" pictures, the background almost fades into white. While this does change how we see the picture, if I were to take data from the "real" pictures and the altered pictures I would get the same result.