The best time to observe the moon is between the time when it's new and first quarter. Tonight it's only a couple of days from full but the evening was so nice I decided to spend some time gazing at it.
When you observe Luna through a big telescope the first thing you notice is that, after a couple of minutes looking at it, you go blind in your observing eye. It's so bright that your pupil stops down and, if you glance away from the eyepiece, you see nothing out of that eye for quite some time. In fact, it takes several minutes for my eyes to recover and to regain a modicum of night vision.
If the moon is not full, there are features illuminated at an angle which provides a sort of modeling to certain parts of the surface. Mountains and crater rims cast shadows and these shadows provide dimension to what you are observing.
I didn't have any grand plans for tonight, just wanted to scan around the orb at high power for a while. As I moved my scope around the terminator, I ran across a very interesting complex of craters, rilles, and mountain chains. The image contained in this post was lifted from a program called Virtual Moon Atlas and, even though it is quite accurate, portrayal of some surface features is a little off.
I've marked the three prominent features in this complex (click on the image to make it bigger). The crater Aristarchus, about 24 miles in diameter, is considered to be the brightest feature on the face of the Moon. It is sometimes visible in the earthshine of a young moon and easily seen with the slightest magnification.
Vallis Schroter is a 97 mile long rille that is unusual because of the circular path it takes on the surface. It's beginning is marked by a crater with an unusual name: Head of Cobra. This moniker apparently refers to the snake-like appearance of the rille.
Montes Agricola is a mountain chain about the same length as Schroter, 97 miles. What's unusual about it is that during certain times a shadow is cast across the mountain by Dorsum Niggli, a "wrinkle ridge' just north of Agricola. If you watch this shadow long enough, it moves (quite slowly but it moves nevertheless), showing the change in phase of the moon right before your very eyes.
Tonight and possibly tomorrow afford the last days of good viewing for this Moon cycle until it gets past full phase and starts to wane. But observing then becomes a late night or early morning practice. For now I think I'll stick with the waxing moon.
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