Mooning in my backyard

by Randy Muller

It was clear today for the first time in many weeks, so I decided to set up my scope in my backyard and spend a little bit of time observing whatever there was to see. With a nearly full moon riding high in the sky, my primary target was obvious. I knew Schröter's Valley and Aristarchus (a very bright crater) would be in a good position, and I always enjoy looking at this mysterious and interesting region.

It was relatively warm, but very dewy. My backyard was dripping and squishy wet from recent rains.

Before launching into my planned program, and destroying my semi-dark adapted vision, I took a quick look at some multiple stars, beginning with mighty Rigel. I moved on to Sigma Orionis, a star which represents to me a small dagger hanging from Orion's belt. Although there are supposedly 5 components to this multiple star, I only noted 4.

I took a look at the Trapezium, a compact cluster at the heart of in the Great Nebula in Orion (M42), a collection of 6 stars. The nebula itself was disappointing, being washed out from light from the moon and suburban light pollution.

I made half-hearted attempts to find the galaxies M109 and M51, but to no avail. In spite of these failures, I was really enjoying being outside under the stars again. It had been over a month since I was out last.

Finally, I was ready to settle down and enjoy the moon. I used my 7.5 mm plössl, giving 190x, almost exclusively.

SCHRÖTER'S VALLEY AND ARISTARCHUS IN LIVING COLOR

I began serious study in chart 18 of Antonín Rükl's "Atlas of the Moon", with Schröter's Valley and Aristarchus. It looked great, although it was well away from the terminator, so some relief was missing. The long, thick sinuous rille winding around the vicinity of the ultra-bright crater Aristarchus was lovely.

What jumped out at me when I looked, and what I would have certainly missed had the terminator been in the "right place", was the color of this whole region. It appeared to have a dirty yellowish or brownish caste, in stark contrast to the grays and whites of the rest of lit portions of the moon. The color difference was subtle, but was striking when noticed, espeically because there was no color anywhere else on the moon.

I looked in vain for another area with a similar dirty-yellow color. The only "color" differences I noticed were variations of brightness or shades of gray. While I was making this I happened to notice that the eastern (celestial) half of Mare Imbrium is a somewhat darker shade of gray than the western side, and the boundary is a meandering curve that runs north and south, somewhere in Rükl chart 11, either around 19°W or 13°W. (I'm not sure of this, since I'm writing it from memory.)

A ways to the north of Aristarchus lay what I thought was a nice looking dome, but it is identified in Rükl chart 8 as Mons Rümker, which apparently is a full-fledged mountain. It sure looks like a dome to me!

SUNRISE IN GRIMALDI AND HEVELIUS

As I scanned along the terminator on the eastern limb of the moon, I ran into an interesting area where sunrise was occurring, and the scene was changing slowly even as I watched it. (Rükl 28) The sun was rising in Grimaldi and Hevelius. Grimaldi was relatively flat, but Hevelius was pocked with craters. As the sun rose higher (and as I looked at it longer), I began to see a fine array of rimae criss-crossing the floor of Hevelius.

It was very beautiful and delicate looking.

One rille even went up and crossed the rim of the crater and continued south, outside the crater. These rimae became prominent at about 10:18pm (6:18 UT).

As I was observing this area, a flight of ducks or geese silently crossed through the field of view. They were very high, and heading north.

FILLED TO THE BRIM

Just before I quit, I scanned further south and noticed the odd crater Wargentin (Rükl 70), which is filled to the brim with mare material. It looked oddly inverted compared to the craters near it.

Using a lunar atlas to identify features at the scope is a tremendous help in getting a grasp on the flood of detail which confronts the lunar observer. At first, I was just gawking at everything, overwhelmed by the detail and brightness. Gradually, I was noticing the same things again and again, and began to log my impressions.

Packing it in for the night, I was very pleased to have this time to familiarize myself with some more very intriguing lunar features. And David North is right: This is a fabulous time of the year to look at the moon, because it is very high in the sky, well out of the atmospheric muck at lower elevations.

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