20051017 – Young Decrescent

Session Name: 20051017.2045

Location: 59th & 6th, Entrance to Central Park, NYC
Site Classification: Urban
Date/time: 17 Oct. 2005, 8:45pm ~ 11:00pm
Eqpt. The Travel Pack
- Handheld Binos – Fujinon 7x50
- Tripod mounted Binos: Takahashi 22x60
- Tripod mounted Tele Vue Ranger (TVR), F/6.8 480mm refractor
- EPs: Plossl 20mm [24x, 2.1◦] & Nagler 9mm [53x, 1.5◦]

NELM – no attempt

Weather conditions were similar to yesterday, as judged by those annoying high cirrus clouds that caused a bright sky glow around Moon. The halo was nuisance when moving Moon out of the fov, so I simply avoided any observing nearby.

I brought my travel pack and setup again on the NW corner (reported incorrectly yesterday as the NE corner). The travel pack is my Kelty backpack that comfortably fits both bins and the TVR, along with accessories. I can either carry the tripod in a free hand or securely strap it along the side of the pack. It is light, convenient to travel, set up and breakdown. Much different than bringing the larger scopes – Tak FS102 or TP10. Coming to this location is great for this pack since it is a 5 minute walk from my home.

This corner is on the beaten path and my presence attracts attention and encourages curiosity. I can feel it from the pedestrians walking by, but not as many as I expect stop. I am not the inviting kind, as I am concentrating on observing and recording notes. If one happens by and asks what’s up, I pause, chat and share the view with them. This evening about 18 persons had a look at the Moon and some saw Mars. One gentleman was a “sticker”, he stayed for more than a half an hour up until I packed it in. The most remarkable was the cab driver who pulled up and asked if he could look at Moon, he had never looked through a telescope. He asked much. Nothing. He took a quick look, I sort of wished he looked longer. He offered me some money which I refused and replied that it was my pleasure.

Responding to another man’s question, I told him we were looking at Moon. He said that’s all, just the Moon. He was invited to look through the telescope and I heard him speaking to himself words of amazement. I said pretty impressive, our celestial brethren, beautiful sight, we even sent men there. He finished the thought with, “And we brought them back!” He continued speaking by saying when he’s faced with challenges at work he reminds people that we sent men to the Moon and brought them back, now what problems can’t we solve here? As he left with his family, he smiled and I sensed that this experience substantiated his belief in some way.

My goal tonight was to continue to observe Moon along the eastern limb, being that libration is favorable. Prior to going out, I read about the 15 day Moon in The Photographic Atlas of the Moon by Chong, Lim, Ang. There described was a passage about the instantaneous Full Moon and how one may detect the Terminator after Full Moon. This stuck with me. During my observations I would detect this, considering it a crescent terminator, and not much farther flung as the Decrescent Moon.

“Young Decrescent Moon” can’t be a new moniker. I am sure someone has expressed this before, describing a growing terminator, opposite to sunlit crescents, young or old. This was a young decrescent since it is waxing to new Moon; or in more proper terms, relative to the sunlit portion, Moon is waning. My observations were done with both the Tak bins and the TVR. The details described below were evident in the bins but the TVR really brought out details under magnification for better study. The following details are based on the TVR views. I estimate the decrescent subtended 90◦ ~ 100◦. The horns from just west of Mare Humboldtianum down to about 4:15 where a lip was observed, just below crater Lyot in Mare Australe.

Without going into much detail, 3 features – craters Hayn and Endymion, and Mare Humboldtianum - constituted an anchoring triangle that I could regain my bearings and work from. In my fov, Moon’s appearance and orientation in the refractor was that Hayn was on my 12:00 to 6:00 mental reference line, Tycho on the south end. Relative to this reference line, Endymion was the most central to this, Hayn ever so slightly towards 1:00, that is 12:05, and M. Humboldtianum was cheating to the east.

Crater Hayn was where I suspected the decrescent’s horn to begin. It was right on the terminator and the crater is so foreshortened on a favorable librating limb, that it was capable of expressing relief that one generally associates with the terminator.

Mare Humboldtainum’s upper, eastern wall was on the terminator, its rim brightly lit up.

In my notebook I drew a line, as opposed to a circle which would represent a crater, in the area where Mare Marginis may have been but no other notes remark on it. Mare Smythii was spectacular in the terminator. I noted that its length was almost as large as Mare Crisium’s length. Just like mountain peaks observed along the terminator, a part of M. Smythii’s southern rim peaked above the terminator looking like an orphaned jewel beyond the terminator. This was noticed in the Tak bins. The huge smooth floor crater contrasted nicely with long rim extending along the limb. In the TVR, I could see a crater embedded in the wall of the northern rim.

I think it is crater Neper that neighbors M.Smythii to the north. In the Tak bins, a central peak was easily observed. In the TVR, I could see a second mountain peak further north in the partially shadowed floor crater.

There was a lot to see as I tried to sketch Moon again. Not good. My scale is way off, even when I place objects relative to one another. Seems that the errors accumulate rather quickly in the 2½” template I use. This needs to be bigger.

I suspected that the opposing horn of the decrescent terminated near Mare Australe. There was chunk taken out of the limb, more like a step. This was located around 4:15 in my fov, below M. Australe. Also, my sketch shows that Australe is well within the limb, so I sense that libration is rotating down along this area. In contrast M. Humboldtianum was high up on the limb, and Hayn looks like it will roll over to other side real soon.

I observed Mars for a fair bit, though I wish I had a larger scope and higher magnification. I observed Mars with only the TVR, and like Moon, exclusively with the Nagler 9mm. I could see a large dark patch across the middle and lower half of the disk. At times, it looked as if there were two dark specks, nipples standing out above the rest of the blotchy area of Mars. . To the north, I was certain that I saw darkening. Occasionally, I thought I did, but it was not consistent and lasting, so I only mention the experience. This was the first time I was satisfied with what I saw of Mars. Prior, I have seen Mars a handful of times with the Tak refractor or TP10, but what I remember of the seeing was not impressive. The dark feature was apparent in those scopes but now that Mars angular diameter is increased, I wonder if more is available from them. If I make my way out again tonight, I’ll probably bring the Tak for Mars viewing.

One other object I’ll note is Mesarthim. Since I was in the neighborhood of Moon, I first thought of returning to zeta Psc, and seeing how far Moon traveled. It fit within one Tak bin fov (2.1◦) away. More than 12◦ it moved past, so I change tack and went to gamma Ari. In the bins, it was a pretty composition of this equally bright white double with a fainter reddish star ESE of it, maybe ¼◦ away.

peter