THE RISE AND FALL OF LUNAR OBSERVING
Kevin S. Jung
Argo Navis Observatory
In the distant past, our ancestors looked up at the sky with awe and wonderment. The moon was of special interest, as it appeared to change its brightness and shape, and it also reappeared with great regularity in the sky. Since that time, man has strafed to learn more about our nearest celestial neighbor. I. Ancient History
At the beginning of recorded history, it was known that the passage of time could be decided by observing the positions and phases of the moon. The idea that the moon was not perfectly smooth can be traced as far back as approximately 450 BC, when Democritus believed that there were "lofty mountains and hollow valleys" on the moon.
Selenology, which is the astronomical study of the moon, began around the year 300 BC, when the Babylonian astronomers accumulated enough observational data about the moon that they were able to predict the time of lunar eclipses. This appears to be the first time that events could be predicted based on observations occurring over a long period of time. It took until approximately 450 BC however, before the phases of the moon and the phenomena of the lunar eclipses could be explained correctly.
At approximately the same time that the phases and eclipses were being understood, the Greek astronomer Hipparchus, using observations and mathematical formulae, measured the distances to the moon as well as the sun with surprising accuracy. Clearly, the age of scientific observation of the moon was slowly picking tip interest.
The end of the Fifteenth Century was apparently when serious study of the moon began. Around 1603, William Gilbert compiled the first lunar drawing based on naked-eye observations. Others soon followed, and when the telescope made its appearance on the scene, drawings were begun that at first were not very accurate, but soon became better as optics improved. In 1687, Isaac Newton stated that the moon's motion was due to the forces of gravity.
Other theories and discoveries were soon to come. In the early 1700's, the librations of the moon were measured, showing that more than fifty percent of the lunar surface was visible to observers. In 1750, Johann Meyer produced the first relatively reliable set of lunar coordinates. This would enable astronomers to locate certain features on the moon by their coordinates, making measurements of lunar features easier.
Selenography, the study of the physical features of the moon, officially began in 1779 when Schroter started making meticulous observations and measurements of the lunar features. Others soon joined him, and the systematic measurement of craters and other features was under way.
All of the measurements were done by direct observation, with detailed drawings supplementing the observations. Then, in March of 1840, J.W. Draper, using a five-inch reflector, produced a Daguerreotype of the moon and thus introduced photography to the astronomical world. At first, the images were of very poor quality, but like with the telescope two hundred years earlier, they very quickly became better. By 1890 lunar photography had become a recognized branch of astronomical research. Now, the astronomers could use lunar photographs to obtain precise measurements without having to stare through the telescope.
The Twentieth Century brought more advances to study of the moon. In 1946, scientists turned a radar dish to the moon and for the first time received a return signal, thus enabling astronomers to use this new technology for things other than for military means. Telescopes became bigger and better, computers were beginning to be used, and rockets and missiles were being launched to study the upper atmosphere of the earth. Then in 1957, the Soviet Union launched Sputnik into orbit, beginning the race for space. The United States soon followed suit, orbiting their own satellite, Explorer I.
Soon even bigger rockets and heavier payloads were launched, and on September 13, 1959, the Russian spacecraft Lunar 2 impacted in the Mare Imbrium area of the moon. Scarcely one month later, Russia's Luna 3 sent back the first photographs of the other side of the moon, giving the world the first glimpse of the until-then unseen side of our satellite.
Other missions followed. The United States sent Orbiters to photograph the moon, Rangers to take photographs right down to the instant they impacted on the surface, and Surveyors to take photos and soft land on the lunar surface. All of these missions sent back photographs that were of increasingly better resolution. Then on December 24, 1968 Apollo 8, with astronauts Anders, Borman, and Lovell, became the first Earthmen to orbit the Moon, giving the people back on earth their own impressions and observations of the lunar surface. They were followed by Apollo 10, which stayed in lunar orbit far longer, giving us a glimpse of things to come.
Then on July 20, 1969, the world held its collective breath until finally, in the middle of the afternoon, Neil Armstrong said, "Tranquillity Base here," signifying that man had landed upon the surface of the Moon. Then, at 10:56 PM Eastern Time, Neil Armstrong stepped onto the surface with the now familiar words, "That's one small step for a Man, One giant leap for Mankind." Soon afterwards, Edwin Aldrin joined Armstrong outside the Lunar Module to set up experiments and obtain samples.
Apollo 11, and the missions that followed, marked the peak of lunar observation and exploration. The samples that Apollo 11 returned to the earth were found to be made of mostly basaltic rock, approximately 3.7 billion years old. Based on any samples returned by the other missions, there does not seem to be much (if any) sedimentary structure in the moon.
Many other items of data were obtained over the years. The diameter of the moon is approximately 3,476 kilometers, and its orbit ranges from an apogee of 406,730 km. to 356,400 km. at perigee, with a mean distance from the earth of 384,400 kilometers.
Certain aspects of the moon continue to battle astronomers. It has been found that the full moon, instead of having twice the illumination of the first or last quarter moon, is in fact almost NINETEEN percent brighter.
Other mysteries concern lunar features that have apparently changed. One of the most famous cases concerns the lunar crater Linne in the are of Mare Serenitatis. In 1834, the German astronomer Lohrmann stated that the crater can he seen under all angles of illumination, and is the second most conspicuous crater on the moon. The astronomer Madler observed an interior shadow when the sun had attained an angle of thirty degrees, so the crater must be deep. Schmidt also showed the crater on drawings during the years 1841-1843. Then on October 16, 1866, Schmidt observed that Linne had somehow disappeared. Where once was a larger crater, there was instead a small whitish patch. It remains like this to this day.
Another subject concerns Lunar Transient Phenomena. For years, amateur astronomers have reported seeing strange colors on the moon, especially in the Alphonsus and Aristarchus regions. These types of observations gained credibility when on November 13, 1958, the Soviet astronomer Nikolai Kozyrev saw a brightening at the central peak in the crater Alphonsus. He photographed its spectrum, which showed carbon-vapor emissions. Suddenly amateurs appeared to been vindicated. These areas are still of interest today. During the Apollo 11 missions, Houston Control asked the astronauts to observe Aristarchus, as events had recently been reported by astronomers. These areas are still under observation by the lunar section of the British Astronomical Association and the Association of Lunar and Planetary Observers in the United States.
Since the lunar landings, interest in observing the moon has dropped off considerably. Although some amateurs still do lunar observing, many of them observe deep sky objects and would rather not have the moon in the sky. This is too bad. I am afraid that until the last few years, I have been guilty of this also. In the early 1970's, I could name all of the main features on the lunar surface, but today I can't. If it weren't for Gary Ross, who got me interested in doing lunar occultation work, I would still be overlooking our nearest neighbor. During the last year or two, I have been relearning the lunar features because I look at the moon every time I do occultation work.
I think that many amateurs do not look at the moon because they think it doesn't change, but that is wrong. Because the Sun angle and illumination on the moon isn't always the same, certain features may remain invisible under certain angles of illumination. Just last year, Gary Ross and I observed Rima Cauchy in Mare Tranquillitatis. The day after, because the Sun angle had changed, that feature wasn't visible. You never know what the moon will look like at certain tines. It is true that on the whole it doesn't change, but subtleties do occur and need to be observed. If you look at the whole picture, you will of course miss the details.
Hopefully we can renew interest in the moon. Maybe in the first part of the Twenty-First Century we will see colonies on the lunar surface. To overlook and abandon the moon would be one of the worst things that Mankind could do. Let's hope that it doesn't happen.