Lunar observing, 6/2
By Randy Muller

The more I observe, the more I like astronomy, and the more I like astronomy, the more I observe.

The skies were clear enough Tuesday night for me to view the 8.4 day old moon, 1 day past 1st quarter, which I have not observed before, due to weather and being relatively new to lunar observing.

I've wanted to observe the area in the Appenine Mountains ever since an observer on the Shallow Sky mailing list reported his observations of the Apollo 15 landing area on May 3.

Also, my Dad had a poster of the moon which showed the moon in two halves, first quarter and last quarter. An inset showed the mysterious Straight Wall. I've always wanted to look at this with a telescope.

I'm also learning better techniques of observing and identifying features on the moon. This night, I placed the table containing my lunar atlas and eyepieces right next to me as I was seated at the eyepiece. When I use my dob, my table stands a distance away from the scope, so that I can freely move the scope around large areas of the sky.

When observing the moon, the scope is mostly in the same position, so I can put the table close by.

What a treat! A veritable feast of changing detail awaited my eyes! The detail is overwhelming, and I find I can only focus on a limited number of things.

I found that my 7.5mm Ploessl (413x) was the most used eyepiece for the evening. I tried my 10mm with a 2x barlow (620x), but no added detail was perceived -- the blurriness just got bigger.

Alphonsus

The great trio of Ptolemaeus, Alphonsus (Rukl 44) and Arzachel (Rukl 55) stood out prominently.

The easternmost (selenographic) of Rimae Alphonsus was barely visible as a meandering white line at my limit of detection, visible about 50% of the time. Using averted vision helped a little bit, though I noticed I wasn't averting my eyes as much as I do with deep sky objects, and the improvement in visibility wasn't nearly as great.

Herschel was also very prominent and had obviously deeper walls, because it was deep in shadow, creating nice contrasty pock mark above Ptolemaeus.

Crater Muller made a nice little inverted Mickey-Mouse shape with its two small ears (A and O). This crater is halfway between Ptolemaeus and Hipparchus. Not a large or prominent crater, Muller is surrounded by giants from astronomical history.

Arzachel (Rukl 55) has great looking terraces.

The Straight Wall

I moved south and slightly west to arrive at the circular pocket of Mare Nubium (Rukl 54) which contains Rupes Recta (The Straight Wall). The Straight Wall was immediately recognizable as a relatively long, straight, thick black shadow. The shadow was not uniformly wide, being somewhat narrower at the north. The overall thickness of the shadow was probably between 10% and 15% of its length.

Rima Birt was also visible, short and infinitesimally thin compared to the Straight Wall. It was just a gently curving line of contrast.

Rima Hyginus, et al

Moving NE, I 'discovered' Rima Hyginus (Rukl 34) by accident. Rukl also has a great photo-drawing of this area on photo #23/24 on page 200. I couldn't see this much detail, of course, but I did notice that it was very prominent, and showed the connected sequence of 'holes' in the section heading NW. The E wall was black and the floor/west wall was very bright.

Rima Ariadaeus was noticeable as a wide, broken 'gully' than went over ridges, busting the illusion that this was a waterway.

The section of Rimae Triesnecker that parallels Rima Hyginus was faintly visible.

Man On The Moon

Continuing NE, I took a little detour to inspect the Apollo 17 landing site (Rukl 25), which I had looked at on May 31. The illumnation was totally different now -- all the shadows were gone, and it looked very flat and not too interesting. The valley was slightly darker than the bright mountains surrounding it, and the crater Littrow stood out in much better contrast than it did on May 31.

Heading E, I reached the Apennine Mountains, the site of the Apollo 15 landing (Rukl 22). The mountains were casting enormously long shadows on the floor of Mare Imbrium. One of the mountains, Huygens or Ampere, was casting a particularly long, double-peaked shadow. It was interesting to observe the shadow revealing details of the topography that I could not otherwise perceive.

The sun was rising over Archimedes, and the floor was deep in shadow. Apparently flowing from a large spur in the crater wall, some of Rimae Archimedes were visible as meandering rivers from the Archimedes 'delta'.

Rima Bradley was obvious, as were Rimae Fresnel to the NE. There was a lot of shadow in the part of the Putrid Marsh (I _love_ lunar nomenclature!) near Hadley Rille, but the rille was barely visible on the NE edge, near the Apollo 15 site.

I remember the TV commentators remarking 25 years ago about some of the problems posed by the Apollo 15 landing. Normally, the lunar module would fly in backwards, face down to its landing site. This time, they flew in face up, because mission controllers thought the view of the lunar mountains rushing beneath the astronauts at very close range would cause them to freak out.

The terrain in this area is extremely rugged, then plunges to the flat floor of the Putrid Marsh. This was a very interesting area, and I spent lots of time here.

The Lonely Mountain

Continuing N, I looked at Mons Piton for a while. In high school, we did an exercise where we measured the height of this mountain. In the low sunlight, it cast a very long shadow indeed. It reminded me of the Lonely Mountain, where the dragon Smaug lived in "The Hobbit", by JRR Tolkien.

A little further north lay the Vallis Alpes, which looks like a giant gash in the Montes Alpes. I don't know how it formed, but it looks like an asteroid grazed the moon there.

Changes

I headed back to Mare Nubium and the Straight Wall and was surprised to see that the shadow of the feature was much thinner, about an hour and a half after the first time I observed it.

I also checked out Mare Smythii and Mare Marginis at the eastern limb, and noticed that they were both closer to the limb than they had been on May 30. Once again, Selene transfigured herself before my eyes.

I also noticed, for the first time, Mare Australe at the limb.

Finally, with the moon setting and the seeing gradually getting worse, I wrapped up the session by looking at the Apollo 11 landing site. I don't think you could find a greater contrast between a conservative, flat, close-to-the-equator, boring site (Apollo 11) and a daring, mountainous, far-from-the-equator, facinating site (Apollo 15).

I could not see the small craters Armstrong, Aldrin and Collins.

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Date:         June 2, 1998 10pm-12am (0500-0700 June 3 UTC)
Location:     Backyard in Roseville (near Sacramento), CA 121W 16', 38N 44'
Instrument:   Intes MK-91 9" f/13.6 Maksutov-Cassegrain
Oculars:      7.5mm Sirius Ploessl
Seeing:       7/10 really wavy, but sharp
Transparency: 6/10 some low clouds