I took out the 20cm SCT for some lunar observing last evening and just thought I'd share some of my observations with you. The moon is a waxing gibbous at the moment three days short of new.
Gassendi:
This is the so called diamond ring crater, with Gassendi A forming the jewel. A is deep in shadow at the moment and the diamond is jet black. At x200 the central dome of Gassendi is split into 3 distinct parts with deep black shadows criss-crossing the domes. The shadow of the dome is projected onto the floor showing the rounded shape quite beautifully. On the western wall there is extensive terracing that is being exposed by the rising sun. The rimae, cracks running along the crater floor, are most prominent in the southern section and easy to follow.
Schiller:
In the southern highlands Schiller is a very elongated crater, it reminds me of a stretched out pear, the sunlit wall and the shadow meet at a point so that the northern half of the crater is split 50-50 black and white. The small portion of the floor that is visible showed a perfectly smooth surface.
Philolaus:
This crater lies high to the north, in the polar region, and as a result the sun does not penetrate to the floor. It is the walls of the crater that hold the interest. The western wall is brilliant white, but there is one large terrace that is a black slash against the snowy white background. Philolaus C is an older crater to the south, Philolaus overlaps it as a result of being a later impact. With the sun at a low angle the southern wall of C casts a shadow onto the outer southern wall of Philolaus, and gives a curved shape, the overall appearance looks like a weather symbol for a hurricane.
Plato:
The floor of Plato looks flat and featureless, but there are craterlets there, and they are small, around 2km in diameter meaning they are a great challenge to see. Higher magnifications of x200 and x400 did not reveal them, the scene was washed out. I stepped down to x133 and inserting a 13% neutral density filter, I was just able to pick out one in the heart of the crater. It required averted vision to become barely visible. I believe it's an achievement to see such a small feature, the lunar equivilent of a 14th or 15th magnitude galaxy.
My 32mm eyepiece give a magnification of x62.5 and the entire globe of the moon just fits into the field of view. Inserting the filter the glare is toned down and it makes it easier to pick out the crater rays. Each time I look at Copernicus I'm reminded of a child throwing a tantrum while drawing with crayons. All around the crater there is a jumbled mess of scribbles with some rays jetting off on straighter trajectories and there is no pattern to the work. Tycho's rays look more orderly and it's interesting to see them cross the moon's surface, with one ray stretching as far as the Mare Nectaris. One can only imagine the force needed to hurl material such a vast distance and what a sight it must have been to watch the impact.
If anyone is interested in serious lunar observation, then I would recommend Antonin Rukl's Atlas of the Moon. It is incredibly detailed and with it you can't get lost.
A long winded post, but I hope you understand my passion for the moon.
Paul
Programming today is a race between software engineers striving to build bigger and better programs, and the universe trying to produce bigger and better idiots. So far, the universe is winning.
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