Bailly -- a Lunar Observation

Date: 02 January 2007 U.T.
Time: 4:30 - 5:00 U.T.
Telescope: 80mm f/5 refractor
Magnification: 65x
Seeing: Good
NELM: 4.5
Temperature: +15F (-9C)



The above sketch is 'mirror reversed' -- the way things look when a simple, mirror diagonal is used with an astronomical refractor. East is roughly up. North is roughly to the right. The moon was a little more than one day away from being in its full phase.

At 65x the entire moon was visible in the refractor's FOV. Yet, the sketch shows a very small fraction of the moon's visible surface. The largest feature in the sketch is the walled-plain "Bailly." Bailly is the largest walled-plain on the Earth-facing side of the Moon. Its position on the Moon is: 66.8 degrees South latitude, 69.4 West longitude. The three large craters shown above Bailly are, from left to right, Kircher, Bettinus, and Zucchius. Those craters are each roughly 70km (44 miles) in diameter.

The sketch was fairly quickly executed and is the first lunar sketch I've made in quite a long time. A quick comparison of the above sketch with the actual 'at the telescope' sketch reveals that Bailly appeared more foreshortened with a narrower floor and walls than depicted in the sketch above. Perhaps I'll use the original for a somewhat more accurate sketch at some later date . . .

As I worked on this observation I found myself wishing I had set up a larger, higher quality telescope. Nevertheless, the sketch gives some idea of what can be seen on the moon with a small, relatively inexpensive telescope.

The telescope was set up on a porch. My fully shielded porch light (which is almost always turned off) was turned on to provide brighter (than that provided by moonlight alone) illumination on my clipboard.