Sunday, October 08, 2006

20061007 - Moon persists in spite of clouds

Session name: 20061007.2155
Location: Top of the Lawn, Central Park, NYC
Moon Age/Illumination: 15.6 days/98.6%
Conditions: Clouds came and went all night long from overcast to mostly clear. Some boiling on lunar limb. When clouds cleared transparency was very good. All 7 Little Dipper stars & the usual suspects in Cassiopeia, Perseus, Hyades, and Pleiades.
NELM: 5.2
Copanions: Charlie, Kin, Hawaian George
Dog walkers: Carole, Andy, Diderot

This session we concentrated on Moon. Even though the clouds were a distraction all night we were able to get in some of the brighter deep sky objects and mostly Moon. The clouds did not hide the lunar disk rather attenuated the glare to make for some nice naked eye observations and also for some delightful study in the scope.

Naked eye we could see Mare Crisium detached from the three prominent maria on the lunar eastern hemisphere and a large white bright patch where Tycho sits prominently the southern hemisphere. Personally I couldn’t resolve Tycho to a precise spot because there was a lack of contrast to distinguish the crater from surrounding ground. However, on the western hemisphere Copernicus, Kepler, and Aristarchus were clearly seen. Charlie was able to resolve Grimaldi but I couldn’t see it. Below Oceanum Procellarum Maria Nubia and Humorum were visible but not like a detached feature as displayed by Mare Crisium.

For the first part of the observing session the Tak 22x60 binoculars were on the tripod to observe brighter DSOs descending in the west. When clouds moved in Moon was the obvious object to check out.

Spectacular! Moon looked spectacular framed in that 2.1° field of view. The disk was full bright but no glaring because of the clouds and the terminator offered beautiful relief of cratering just inside the eastern limb. I didn’t scrutinize any specific area or feature as I did with naked eye or the scope. I just sipped on the view as if my eyes were savoring a lunar bouquet. When Hawaiian George stepped up to the eyepieces, I heard him exhale and utter sounds of wonder.

With Harry 6, the reflector, two eye piece combinations were used: A 2x barlowed TV Plossl 32mm & a Nagler 7mm T6. A huge step between the two but provided two distinct views. In the north Endymion serves as a landmark that I check for libration and as home base for a meandering hike towards Mare Crisium. Craters Hahn (with a central peak) & Berossus were the first to catch my attention. Already lost in the evening terminator, crater Gauss resisted with part of its feature rising above the effects of curvature still shining in the sunlight.

Imagine. Descend the face of this feature and reach a point where it’s lights out! Without an atmosphere there is no twilight, either there’s light and warmth average (224°F/107°C) or the other extreme nighttime and coldness (-243°F/-153C°). Without going into much detail, as those places on Moon enter nighttime, they see a crescent Earth wax to Full Earth over the next 13 ~ 14 days.

While up in the north, we hiked through the dried river bed of Mare Anguis. This irregular shaped mare just north-northeast of M. Crisium looks best as nighttime unrolls on this region. On the rare occasions that I observe his feature under this kind of light, I am struck with the impression of large river bed that winds it way into a wall of darkness.

I still can’t identify a feature that Charlie, Kin and I observed in the south-southeast limb just on the horn of the terminator. I was uncertain if it was part of Mare Australe going into the terminator or if it was a feature more in the southerly direction along the limb. I searched for Clavuis to get my bearings but had a difficult time to locate it as it apparently washe out under the sunlight.

Charlie dubbed one feature, “Palisade”, after the cliffs that New Yorkers can clearly see across the Hudson River. It appeared to be the face of a high crater rim where the top was still painted in light but the face was pitch black. Strangely there were two spots on the face of this cliff that were bright. It didn’t make sense how they could catch light but Moon is a sphere and not a plane.

The southern hemisphere is riddled with craters. I like how the effect of foreshortening increases for craters near the limb. Brightr crater rims interwove with black lined crater floors as if we were getting a peek right over the wall. This really enhances the feeling that we are looking at a 3 dimensional orb in the sky.

With clear skies forecasted tonight, I’m sure that Moon will be on the top of the observing list.


Interested in the Moon for your desktop. This image form Vern's web site has been my laptop's desktop from the day I saw it. From time to time I go back to his lunar archive to peruse the images he shares with us.

If I had to recommend one lunar atlas for the beginner, without hesitation, Photographic Atlas of the Moon, Cambridge University Press, 2002. I am not fluent with Moon and often refer to this after binocular and scope observations. I admit that I complement this with other resources like the Internet or otherbooks but it is usually the first thing I grab for to identify a feature I'm not sure about.

This atlas is great for anyone learning and exploring Moon day by day. Typically four pages provided for each day:
- First verso has a description of a terminator tour, not overwhelming in detail which I like. It makes for the reading light and one can refer to another book book for a denser treatment.
- First recto is a 3/4 page photograph with markup notating the features described. The lower quarter page lists all the features notated in the photograph.
- Second verso has a collection of close-ups and photograph specifics of the features.
- Second recto has the same image as the First recto without any marks.

What I like most is the light writing and clear descriptions of the features that authors S.M. Chong, A. Lim, and P.S. Ang provide in concert with the bright and readable marked up photograph; nothing like that seen in Cherrington's Atlas. The book is appendixed with organized lists for further reading, lunar features, description of the lunar phases, and a chronology of mapping Moon.