Fantastic areas on the Moon

FOREWORD. Yes, everyone knows the Moon is a desolate and rugged place, but for the artistically inclined and imaginative lunar observer, the surface of the Moon holds a certain kind of fascination. For me, this fascination stems principally from the minute and hourly changes a lunar feature undergoes due to the angle of sunlight falling upon it. Next, comes imagination!

Unfortunately, several days either side of the Full Moon phase our lunar companion does take on an appearance this is truly dull and uninteresting. And while the light of a full moon may delight those deeply in love, the light is now so uncomfortably bright that any thoughts of telescopic observation must be put aside temporarily.

Showcasing interesting areas on the Moon is not a new idea. For instance, fifty such areas are illustrated and described in, Atlas of the Moon, by Antonin Rukl. And borrowing upon that idea, I thought it would be fun to put together my own "album" of interesting lunar features.

Perhaps I am wrong, but the lunar features described herein should be easy to find by both beginner and casual observer. And possibly, in the future, another article can be devoted to examining lunar features exhibiting even finer detail.

Equipment. For all my own astronomical observations I use a 6-inch refractor working at f/10. And for lunar sketches I employ a 7.5 mm Plossl eyepiece (Celestron) coupled with a 2x "shorty" Barlow (Celestron), and star diagonal.

As far as filters are concerned, I have found neutral density filters or even a polarizing filter can come in handy, but I do not use them extensively. The filters I have are: 50% T - Density 0.3 (Dark); 25% T - Density 0.6 (Medium); and 13% T - Density 0.9 (Light). Celestron produced all three filters, as well as, the Polarizing Filter Set.

Area 1. Autumn had arrived and on this particular October evening the First Quarter Moon was nicely placed for observation. After scanning the lunar surface I soon turned my attention upon an odd looking area made up of the craters Cuvier, Licetus, Heraclitus, and a neighboring crater labeled "D".

At the time, it appeared to me that several ridges ran parallel through Heraclitus to the craters Cuvier and Licetus. And for some crazy reason, the grouping of both craters and "ridges" reminded me of the remains of an ancient trilobite. Crater "D" formed the "head" and Heraclitus comprised the "body".

NOTE: A fairly good photograph of this area can be found near the center of Plate 14a in the Hatfield Photographic Lunar Atlas, edited by Jeremy Cook (1999).

The crater Heraclitus was named after the Greek philosopher, who lived between 540 - 480 BC in the city of Ephesus, in Western Asia Minor. Heraclitus is described in Rukl's book as being a "ruined" crater having a mountain range down the center. Also, numerous minor depressions abound either side of the mountain range. Heraclitus has a diameter of 31 miles or about 50 km and is 9500 feet deep.

Cuvier is a flooded crater named after Georges Cuvier (1769 - 1832). Cuvier was a French naturalist and paleontologist. The crater has a diameter of 45 miles or 75 km and a depth of 12,000 feet.

Across the way from Cuvier is Licetus, named after Fortunio Liceti, who was an Italian physician. Liceti lived from 1577 - 1657. He was honored with a crater that has a diameter of 45 miles or 75 km and is 9800 feet deep.

Area 2. The next stop this same evening was the crater Maginus. I was very fortunate to observe this crater when only a narrow "V" shaped shaft of sunlight illuminated the central peaks in line with each. The shorter peaks were at the bottom of the "V" while the taller ones stood at the rear. The rest of the crater floor was in complete darkness! Awesome!

NOTE: As with Heraclitus, Cuvier, and Licetus, the crater Maginus can be found on Plate 14a near the center right margin of the photograph, in the Hatfield atlas.

The crater received its name from the Italian astronomer, mathematician, and astrologer, Giovanni A. Magini, who lived from 1555 - 1617. The crater, as with most large craters, is called a "walled plain". This plain is approximately 98 miles or 163 km across and has a depth of 16,400 feet.

Area 3. On the following evening, I decided to scan the areas of Mare Nubium (Sea of Clouds), Mare Cognitum (Known Sea), and Mare Insularium (Sea of Isles). Soon, I came upon another of my old lunar favorites and is located near the outer border of Mare Cognitum. (Mare Cognitum is "sandwiched" between Nubium and Insularium).

This evening, the crater complex resembled a small piece of my tatting or, better yet, a delicate piece of crochet like my mama used to make! And Mare Cognitum makes such a wonderful background!

The area consists of very old "ghost" craters. Barely visible is the large crater called Fra Mauro at one end and the crater Guericke at the other. In between one will find the craters Bonpland, Parry, and a small "u" shaped crater labled "M".

NOTE: A very good photograph of this complex can be found on the lower left side of Plate 9a in the Hatfield atlas. Please keep in mind that the photograph was taken when the Moon was 23.8 days old and that the "lighting" is going to be different.

Let's now learn more about the craters that comprise this complex.

Guericke is approximately 35 miles or 58 km in diameter and is the remains of a walled plain. The remaining part of the crater wall is 3100 feet in height. The German physicist, Otto von Guericke (1602 - 1686) has the honor of having this crater named after him. And In 1654 he demonstrated the existence of atmospheric pressure.

Bonpland is the next crater with its wall broken in a number of places. Rukl describes the floor of the crater as having clefts. Because the illumination was not sufficient, at the time, I am afraid I did not see or notice them.

Bonpland is 36 miles or 60 km in diameter. And is 3300 feet deep in the northeast section according to Ernest H. Cherrington, Jr., author of, Exploring the Moon through Binoculars and Small Telescopes (1984). This crater bears the name of the French botanist, Aime Bonpland (1773 - 1858).

Parry is a crater some 36 miles or 58 km in diameter and is 3800 feet deep in one place. This crater was named in honor of Sir William E. Parry (-1790 - 1855), who explored the Arctic regions and served, as an admiral in the English navy.

Finally, we come to the large, old ghost crater called Fra Mauro. The crater, or what is left of it, is 60 miles or 95 km in diameter. Only a few pieces remain of the eastern wall that is 2400 feet high. On the floor a few clefts can be seen.

Fra Mauro always seemed like an unusual name to me, but I never did take the time to research the name, that is, until now! Fra Mauro (d. 1459) was a Venetian geographer, who prepared a map of the world in 1457 according to Rukl.

Area 4. Two days after First Quarter I found Sinus Iridum (The Bay of Rainbows) favorable for observation! For me, this is truly the loveliest lunar spot I know! I cannot count the number of times I have imagined myself being in this heavenly, secluded spot. Even now, I can just almost hear the imaginary dark, charcoal-gray "waves" as they silently lap at the shoreline. And as I sit on that lovely "beach" I wiggle my toes deeper in the lunar soil, as the Sun makes its slow ascension above the lunar limb.

Sinus Iridum is described as a circular flooded plain about 160 miles or 257 km across and on the backside by is the Montes Jura or the Jura Mountains. The mountains extend 300 miles or 483 km in length and have a height of 12,700 miles or 20,438 km.

At each end of the Jura Mountains are peaks or promontories that jut out into the bay. The higher promontory is called Laplace Promontorium (Cape Laplace) and the lower is Heraclides Promontorium (Cape Heraclides).

Promontorium Laplace was named after Pierre Simon Laplace, the French mathematician, who devoted much of his time to celestial mechanics. He lived from (1749 - 1827). As for Promontorium Heraclides, it was named after Heraclides Ponticus (390 - 310 BC). Heraclides was a student of Plato and believed the Earth rotated on its axis.

According to an interesting note in the Hatfield atlas, one might keep on the look out for the "Moon Maiden" when Promontorium Heraclides is illuminated by the right amount of sunlight! And the reader certainly owes it to him/herself to catch Sinus Iridum at Sunrise (2 - 3 days after First Quarter) or Sunset (2 - 3 days after Last Quarter)!

NOTE: A splendid photograph of the bay appears on Plate 6e in the Hatfield atlas.

Finally, Sinus Iridum owes the origin of its name to the Italian selenographer, Father Giovanni Battista Riccioli, who lived from (1598 - 1671).

Area 5. After stopping to enjoy the beauty of Sinus Iridum I moved the telescope back to near Area 1. Not far from this area is the large crater Clavius. And for some odd reason, Clavius always brings a smile to my face. Perhaps it is that the crater reminds me of a sizeable slice of Swiss cheese! At any rate, Clavius is always easy to find like the face of an old friend in a crowd.

Scattered randomly on the crater floor are smaller craters that stand out quite well when the sunlight is just right. And if the reader has access to a copy of Atlas of the Moon, by Rukl, he/she will find a superb photograph, of Clavius, on page 194.

Clavius ranks among the largest lunar craters and according to Dr. Patrick Moore, in his book, A Survey of the Moon (1963) p. 273, Clavius could be seen with the naked eye when the crater was on the terminator. The crater also has a floor that is convex, according to Ernest H. Cherrrington, Jr., in his book, Exploring the Moon through Binoculars and Small Telescopes (1984) p. 113.

Clavius is a crater that is 135 miles or 225 km in diameter and the walls of this mighty crater rises to a height of over 12,000 miles or approximately 19,311 km above the crater floor. And upon its floor, the observer will find the smaller craters of Clavius D, C, N, J, and JA. Crater JA is the smallest of the group.

NOTE: A detailed description of these smaller craters can be found on page 113, in the book, Exploring the Moon through Binoculars and Small Telescopes, by Ernest H. Cherrington, Jr. (1984)

The craters of Rutherfurd and Porter lie across from each other at the widest end of Clavius. The crater Clavius was named in honor of the German mathematician, Christoph Klau (1537 - 1612).

More to come in Part II

Nancy L. Thomas

NLTsolar@aol.com

10/23/99

"Humble Before The Stars"