Re: moon atlas; questions about moon

brucegooglegroups wrote:
Tonight I was viewing the moon. I had a difficult time matching my view
with moon charts in books . . . and the one from S&T.
www.lunarrepublic.com/atlas/index.shtml is a good site, though.
. . . [O]n the lower side of the moon( North in my telescope?), I
could see one large crater, and six craters near it.
The surface was flat. I also saw two craters directly right on the
edge. Was I looking at the Northern Mare Imbrium?

Your description sounds like you were looking at the crater Plato on
the north edge of Mare Imbrium. The other large prominent crater
visible at that time was Copernicus, but its floor is not a flat plain.
The six craters reference does not ring any bells.

At the time of your post, the lunar terminator was at approx. 40W with
a lunar age of 10.7 days. Henrik Bondo's original edition evening lunar
atlas at:

http://inet.uni2.dk/~d120588/henrik/ela0_sessions.html

contains photos of the Moon by lunar age. That may help you to get
oriented. Bondo's 10.9 lunar day image is at:

http://inet.uni2.dk/~d120588/henrik/ela1_387w_109d_19apr05.html

Using your own lunar hardcopy map or the "lunar republic" map, you can
match up the craters in Bondo's image with their names. The "lunar
republic" image for Plato is B-3:

http://www.lunarrepublic.com/atlas/sections/b3.shtml

Copernicus is on "lunar republic" image D-2 and D-3.

When you begin to watch the Moon, it is typical to have problems
matching the chart to the image do to changes in the apparent view of
its surface. Those changes include:

1) phase change - where the terminator is. See -
http://www.lpod.org/archive/LPOD-2005-02-21.htm

2) parallactic angle - the angle of the Moon's north-south pole and
your local meridian.

3) libration - the Moon's orbit is inclined at 6 degrees to the
ecliptic. Sometimes you are looking "down" on the Moon; at others you
look "up" from below at the Moon. Libration effects range from about 7
degrees of selenographic latitude and up to 10 degrees in selenographic
longitude.

To understand libration, it helps to have a friend stand in front of
you. Look at their face at various angles, including by stooping and
looking up from below, or standing on ladder or stair case and looking
down from above.

A good illustration of this can be found on page 10 of Chong, S.M. et
al. 2002. A Photographic Altas of the Moon. Cambridge Univ. Press. ISBN
0-521-81392-1.

Chong's book is available on Amazon.com.

http://www.amazon.ca/exec/obidos/ASIN/0521813921

Excerpts from Chong's book, including the illustration of libration on
page 10, can be seen online using Amazon's "Search this book" feature.

The process I went through when first learning the Moon was:

1) Learn the major mare phase asterisms using the Astronomical
League's Lunar Observing List:

http://www.astroleague.org/al/obsclubs/lunar/lunar3.html

2) Using a whole Moon chart, like the ARVAL Moon Map, learn the major
fiducial craters that catch the eye on any casual inspection of the
Moon.

http://www.oarval.org/MoonMapen.htm

Some of the major fiducial craters include Atlas, Hercules, Mostling A
(a small crater near selenographic 0 degs lat, 0 deg long),
Ptolemaeus-Alphonsus, Clavius, Tycho, Plato, Kepler, Eratosthenes,
Copernicus, Archimedes, Gassendi, Aristarchus, and Grimaldi.

Then learn the fiducial mountain ranges like: Montes Caucasus, Montes
Alpes, Montes Jura, Montes Apenninus and Montes Pyrenaeus.

3) Using a lunar planetarium program like the freeware Virtual Moon
Atlas,

http://www.astrosurf.com/avl/UK_index.html

follow the Moon each night for one entire lunation. Pay particular
attention to

(a) the lunar longitude of the terminator each night. The Hitchhiker's
Guide to the Moon has a convenient online calculator to tell you the
lunar longitude of the terminator for a particular night.

http://www.shallowsky.com/moon/hitchhiker.html

Virtual Moon Atlas also reports this colongitude of the terminator, and
has tools that identify the major cool things to look at along the
terminator.

(b) the eclipitic latitude of the Moon - that partially defines the
libration viewing angle,

(c) how the phase is related to the position of the Moon in its orbit
around the Earth and the rising time of the Moon - first quarter Moon
sets after sunset in the West, third quarter rises in the east in the
early morning hours.

You can even do this online using the USNO "What the Moon looks like"
today.
http://aa.usno.navy.mil/data/docs/current_moon.html

4) Read Dr. Chuck Wood's Lunar Picture of the Day (LPOD) daily and his
monthly S&T column for in depth notes on particular objects.

www.lpod.org

A couple of lunations (monthly lunar cycles) of this and you'll be an
old hand!

When first learning the feature names, it is also helpful (for learning
purposes) to adopt the mindset of 17th and 18th century astronomers how
first named the Moon's features. They viewed the Moon like the Earth -
it had highland continents (terra), oceans (oceanus), seas (mare),
lakes (lacus) and marshes (palus). Headlands (promintorium) stick out
into the "oceans" and "seas". Although we no longer use the former
names of the continents, -

http://www.lpod.org/?m=20060418

- it is helpful to understand the early astronomers' mindset when they
were naming features.

Hope this helps.

Clear skies - Canopus56

.

Relevant Pages

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