Lunar Observations
In a recent article (Sky & Telescope, April 2004), the well-respected planetary scientist Charles A. Wood introduced a lunar equivalent of the famed Messier and Caldwell lists of deep-sky denizens. Wood's Lunar 100 List is a fine blueprint for the observer who wants to be informed about the most noteworthy representatives of significant lunar features.
Be aware however that when looking at the Moon through binoculars or a telescope the angle of the Sun's rays striking the surface is most critical in creating shadows -- the presence or absence of which is vital to the proper perception and interpretation of any feature under scrutiny. Next, the shape of an object is highly important to its identification. And the third most important focus should be on the gray tones, which establish an object's texture. These points are the primary objectives of airphoto interpreters who are trained to consciously make the most effective use of shadows, shapes, and tones. Just keeping these principles in mind will help make you an artful observer capable of really enjoying the scenery.
Think about it for a moment and you will soon agree that the best shadows (that is, the longest and sharpest) occur either at sunrise or sunset when the angle of incidence is low. For that reason, savvy lunar observers are most active during these times; meaning that they follow the ebb and flow of the terminator with near-religious fervor as it traverses the Moon's face. In lunar parlance, the "terminator" is the line of demarcation between the sunlit area and the dark area of the Moon's surface. (It has nothing to do with Arnold Schwarzenegger.)
As a courtesy to you when space permits, selected features on Wood's Lunar 100 List will be included in the log only when they have come into prominence shortly after lunar sunrise or just before lunar sunset. Enjoy!
Major Reference Lists
"Pickering's Dozen" is a list from William H.Pickering (1858-1938) giving 12 naked-eye lunar objects in increasing order of difficulty (Astronomy, June 1997). They are: 1) Bright surroundings of Copernicus 2) Mare Nectaris 3) Mare Humorum 4) Bright surroundings of Kepler 5) Region of Gassendi 6) Notch in the Mare Tranquilitatis-Plinius region 7) Mare Vaporum 8) Light area around crater Lubiniezky 9) Sinus Medii 10) Shaded area near Sacrobosco 11) Dark spot at the foot of the Apennines 12) Riphaeus Mountains.
Ernest H.Cherrington (author of Exploring the Moon Through Binoculars and Small Telescopes, 1984) lists the ten most prominent lunar landmarks of major orientation importance. They are: 1) Aristarchus 2) Copernicus 3) Mare Crisium 4) Gassendi 5) Grimaldi 6) Langrenus 7) Plato 8) Posidonius 9) Theophilus 10) Tycho.
Charles A.Wood, a distinguished lunar geologist, recently introduced a list of 100 notable lunar objects arranged in increasing order of viewing difficulty. Entitled "The Lunar 100," the list is analogous to those of Messier and Caldwell. It originally appeared in Sky & Telescope, April 2004.
Lunar Geologic Time Scale
The Pre-Nectarian Period began 4.6 billion years ago when the moon was formed. The Procellarum basin was soon formed (about 4.3 billion years ago) followed by the Tranquillitatis, Fecunditatis and Nubium basins.
The Nectarian Period began 3.9 billion years ago when the Nectaris basin was formed and soon followed by the Humboldtianum, Humorum, Crisium and Serenitatis basins.
The Imbrian Period began 3.8 billion
years
ago when the Imbrium basin was formed followed by the Orientale basin,
which in turn was followed by great lava flows that filled the
Tranquillitatis,
Fecunditatis and Crisium basins 3.5 billion years ago with layer upon
layer
of "runny" basaltic lava.
A second lava flow period seems to have followed
which flooded the Procellarum and Imbrium basins. Large-scale
volcanism
and high impact frequency dwindled significantly by 3 billion years ago
and was seemingly followed by a quiescent period of 2 billion years.
The Copernican Period began with the formation of the crater Copernicus some 900 million years ago. There has been no significant volcanism nor major impacts to speak of since.
On-Line Sites
American Lunar Society
http://www.otterdad.dynip.com/als
American Assoc of Astronomers
http://www.corvus.com
American Astronomical Society
http://www.aas.org
Assoc of Lunar & Planetary Observers (ALPO)
http://www.lpl.arizona.edu/alpo
Astronomical League
http://www.astroleague.org
Astronomical Society of the Pacific
http://www.astrosociety.org
Lunar & Planetary Institute
http://www.lpi.usra.edu
Consolidated Lunar Atlas
http://www.lpi.usra.edu/research/cla
Lunar Orbiter Photographic Atlas
http://www.lpi.usra.edu/research/lunar_orbiter
Lunar Observer
http://users.adelphia.net/~dembowski
NASA Lunar Exploration
http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_25th.html
References
Norton's 2000 Star Atlas, 18th edition, John Wiley, 1989
This venerable stellar bible has large
photographs
of each of the moon's four quarters, annotated, fully
inverted
images.
Turn Left at Orion, Consolmagno & Davis, Cambridge Univ
Press,
1989
Has annotated large photographs of the moon's
stages (5) from crescent through waning gibbous, semi-inverted.
Atlas of the Moon, Antonin Rukl, Kalmbach Books, 1996
This classic atlas (out of print) features
large-scale air-brush maps of the entire surface of the moon, fully
indexed,
naked-eye orientation, descriptive text, coordinates, sizes.
Moon Observer's Guide, Peter Grego, Firefly Books, 2004
This little jewel gives a lunar-day by
lunar-day
guided tour of the moon's features, naked-eye oriented, with maps
sketches
photographs.