The first set of plots below shows the Moon's brightness over about a two week interval, though on only three of those days are the viewing conditions of the Moon really "good." Also shown on each plot is the percent illumination of the Moon taken from JPL's ephemeris generator (here is the output). I would expect this curve to line up with the Moon's brightness, but it doesn't. (Any ideas?)
One can see large variations in the Moon's brightness during each observing period, even with the smoothed images. Data from the first three days (I have not included data from 10 September 2003 since the Moon wasn't entirely in the field of view) are plotted in the bottom three sets of plots. The corresponding column:row number are shown for each data point.
From looking at the individual days' data, it's pretty clear that there is an image plane effect. The Moon gets consistently brighter as it moves across the image plane from right to left. In addition to the right-left change in the Moon's brightness, the Moon also appears to become dimmer as it moves toward the bottom of the image plane. This is particularly clear on 13 September which is probably the "best" viewing day since the Moon is never near the edge of the field of view on that day. In both the LBHL and LBHS images there is an increasing trend as the Moon moves from right to left across the image plane. There is a large drop in the Moon's brightness after the platform angle changes and the Moon is located closer to the bottom of the UVI image plane. There is an upward trend as the Moon moves from right to left again, but it never reaches the brightness it had before the platform angle change. My working hypothesis is that this is due to an incomplete background subtraction and/or an incomplete flat field correction.
Of course, it would also be useful to compare these brightness variations with other solar measurements, e.g., X-ray flux, F10.7, and E10.7.
Any comments, suggestions, questions, accolades, or ridicule are welcome.
From 12 through 23 September 2003
