We have designed, built and installed a small robotically operated coronagraph at a site specifically charted to support robotic telescopes: the Winer Observatory in Sonoita, Arizona. With this coronagraph, we have observed the sodium exosphere out to one-half degree around the Moon every clear night for the past year. An Andover temperature-controlled narrow band filter 1.5 Å wide is centered on the sodium D2 line. A very narrow filter allows observations close to the Moon's surface. The temperature of the filter is controlled, and is adjusted to place the passband of the filter on the sodium D2 line.
This filter would yield a sodium signal at least 24% of the scattered lunar light at first quarter. A series of on- and off-band images of the lunar exosphere are collected each clear night. Exposures of 10 minutes are required to image the sodium corona at good signal to noise. Following each exposure pair, on- and off-band images of the lunar surface are collected by taking a 0.2 sec exposure with the open filter to establish the exact position of the moon's disk.
We will show a time series of the lunar corona over this year long period and determine whether there are long term trends correlated with meteor showers, passage through the Earth's magnetotail and solar storm events.