A Short History of Lunar Cartography by Leslie Bochenski
What's Up in the Night Sky
Well everybody, it looks like the semester is ending with a bang. A lot of us had the chance to observe the beautiful comet Hayukatake. I know that it was a sight that I will never forget. And thanks to the hard work of a few of our members, some of you were able to view the comet from various sites away from the city lights. I know that many cool pictures were taken as well and hopefully we will be able to get some of these up on our web page.
I hope some of you were also able to see this past week's total lunar eclipse. It was weird seeing the appearance of the moon change so drastically in the scope after a mere half hour.
As this semester winds down, I am looking forward to the end of my sojourn at the U of I, but at the same time, I will miss things like my involvement in the astronomy club. I know however that I am leaving the club in very capable hands. It always has been and always will be the members who make our club what it is. If not for your enthusiasm and dedication in coming to meetings and open houses in all sorts of weather, we wouldn't have a club. I know that whoever among you ends up running the club will do a great job.
Finally, I have not forgotten about our upcoming centennial. I am trying to get things together for that as fast as I can, and if I stay here for the summer, I can work on it then. I should have more time towards the end of the semester.
I'll talk to you all later. Have a great rest of the semester.
Our World Wide Web site is still going strong (http://www.astro.uiuc.edu). Set up and run by Web Chair, Dave Nash, it's a cool place to keep up with club activities and a place to see the Electronic Sidereal Messenger. Check it out and let us know what you think!
Finally, I'll end with my never-ceasing battle cry. Send me your articles. If you have something that you think might be of interest to the rest of the club, then send it on in. The best way to send me articles is to e-mail them to me at email@example.com. If that is inconvenient you can also send a paper copy to UIAS c/o the Astronomy Department at the address on the back of this newsletter.
Since ancient times, people have watched the phases of the moon and tried to make sense of its motions. Scientists and philosophers speculated on the nature of its mottled markings. Today, we can look at a calendar to find the phase of the moon; and the Space Age has brought pieces of the moon to Earth so we need not wonder about its composition.
The first attempt to map the surface markings on the moon was made by William Gilbert in the 1590's. His chart, made without the use of a telescope, showed outlines of dark and light patches on the moon's face. Contrary to most of his contemporaries, Gilbert believed that the light spots on the moon were water, and the dark spots land.
Galileo was the first to record telescopic views of the moon. In 1610, he published 5 drawings of the moon, speculating that the light areas were land, and the dark spots water. He also attempted to estimate the height of lunar mountains by observing the lengths of their shadows. His estimates were about 2 times too large. Galileo did not produce a map of the moon, but drew individual features.
Thomas Harriot pointed a telescope at the moon about the same time as Galileo. From 1610 until 1621, Harriot produced a number of lunar maps, but they were not published until the 20th century. Langrenus (Michel van Langren) published a lunar map one-third meter in diameter called Selenographia in 1645. He was the first to assign names to maria and craters, 270 in all.
Each lunar cartographer, or selenographer, devised his own system of naming lunar features, so different maps would often show different names for the same feature. Popular choices included names of scientists, royalty, terrestrial features and cities. Maria, the dark areas generally believed to be seas or oceans, were named for moods. When Hevelius (Johannes Hewelcke) published Selenographia in 1647, he used the names of terrestrial mountain ranges to designate lunar hills. Some of these, such as the lunar Alps, Apennines, and Pyranees, are still used today. Hevelius was also the first to recognize the bright rays, formed by ejecta from the impacts that created some large craters. He also recognized that the moon rocks slightly back and forth, allowing us to see first one edge, and then the other. This gravitational effect is called liberation, and allows Earth-bound observers to see about 57% of the moonıs surface.
Italian Francesco Grimaldiıs lunar map was published in 1651 by Giovanni Riccioli in the Almagestum Novum. Craters were assigned names of famous scientists, mostly astronomers, and philosophers in some way associated with the moon. These names were grouped by age, nationality, and specialty, and many of the names are still in use. By the end of the 17th century, moon maps had become popular items. Some were very detailed, others lacked accuracy, but showed an artistic flair.
During the 1750's, Tobias Mayer, a German astronomer, was the first to construct a moon map using orthographic projection. He also used a glass micrometer to produce charts in sections, and achieved unprecedented accuracy. Trying to determine the moonıs equator, Mayer carefully observed the position of lunar features, and quantified Heveliusıs measurements of lunar liberation.
Johann Schroterıs 10 year study of the moon culminated in the publication of Seleno-Topographische Fragmente in 1802. He was the first to describe rilles, long cliff-like features on the lunar surface. Selected regions of the moon were drawn in unprecedented detail, with the hopes that future observers could use the charts to detect any changes that might occur.
The most accurate and detailed pre-photographic moon map was constructed by J. Heinrich von Madler and Wilhelm Beer in Berlin, who published Mappa Selenographia in 1836. They began by laying out a grid of reference points, and measuring them with a micrometer. Accurate positional measurements were then supplemented with 1095 altitude measurements of lunar mountains. This 1 meter diameter chart, the product of 7 years work, served as the standard reference until the middle of the 19th century, when photography was born.
The first atlases to include photographs did not include photos of the moon itself. The Englishmen James Nasmyth and James Carpenter constructed plaster models of the moon based on telescopic drawings. Photos of the models were published as The Moon, Considered as a Planet, a World, and a Satellite, in 1874. Nasmyth and Carpenter provided not only physical descriptions of lunar features, but tried to describe the origins of the features as well.
In 1839, Louis Daguerre, inventor of the pre-photographic process known as Daguerreotype, produced an image of the moon on a silvered plate. Due to the long exposure time, the image was little more than a blob. The first successful photos of the moon were taken by John William Draper in New York in 1840. He presented his efforts, obtained with a 5-inch telescope on silver plates, to the Lyceum of Natural History of New York (now the New York Academy of Sciences).
Harvard Observatory photographed the moon from 1849 to 1851. Using the 15-inch refractor, the image at prime focus was 2 inches across. In the years that followed, De la Rue, Grubb, Rutherford, Secchi, Gould, and Henry Draper continued to improve astronomical photographic techniques. But the art of photography was still in its infancy, and there were problems to overcome. The emulsions available were not very sensitive to light, so exposures of up to a minute were needed to record the moonıs image. During exposure, the moon would move in the field of view, and blur the image. With the aid of a tracking telescope, this motion could be overcome, but vibrations in the telescope drive, stray light, and turbulence in the earthıs atmosphere would still degrade the image. In 1871 the invention of the dry bromide photographic plate, which was much more light sensitive than the silver plates, reduced exposure times to less than one second.
With this development, astronomical photography was soon being practiced at observatories the world over. In 1896, the Lick Observatory Atlas of the Moon was published, using photographs taken by Edward Holden with Lick's new 36-inch refracting telescope.1 From 1896 to 1909, the Paris Observatory published the Atlas Photographique de la Lune, containing 80 plates taken with a 34-inch refracting telescope. The original and subsequent editions of this atlas dominated the early 20th century. William Pickering of the Harvard Observatory published a Photographic Atlas of the Moon in 1903. This contained images of the moon at different phases, allowing study of features at different angles of illumination.
By 1921, lunar nomenclature had become a frustrating problem. A single feature could have up to three names, depending on which the atlas was consulted. The International Astronomical Union (IAU) formed a committee to investigate the problem. Their work culminated in Named Lunar Features, published in 1935, also known as the IAU Map. The Map followed the guidelines set down by Von Madler nearly a century before. These included naming craters after scientists, mostly astronomers and physicists; naming mountain ranges after earthly counterparts; and using the Latin versions of moods and feelings for the maria. Smaller craters were designated by the name of a nearby large crater followed by a Roman letter, and individual peaks were assigned Greek letters. The system was extended and improved under the direction of Gerrard Kuiper at the University of Arizonaıs Lunar and Planetary Laboratory, and officially adopted by the IAU in 1967.
In 1964, photos from Lick, Mount Wilson, Pic du Midi, and Yerkes Observatories were used to produce the Rectified Lunar Atlas. For it, the original photographic plates were projected onto a sphere and re-photographed from above to produce images free from the distortion caused by the spherical surface of the Moon. The Rectified Lunar Atlas and subsequent Consolidated Lunar Atlas were the last major moon maps produced using all Earth-bound telescopes.
With the dawn of the Space Age, cameras were sent to the moon. In 1964 and 1965 NASA launched a series of Ranger probes, which relayed hundreds of photos to Earth before crash landing on the moon. 1966 through 1967 saw the success of Surveyor probes which were designed to soft land on the moon, to prove that a manned spacecraft could do the same. Seven Surveyors landed, sampled the lunar soils, measured radiation, and photographed the moons surface.
The lunar orbiters also gave us a look at the previously unseen far side of the moon. This was first photographed by the Soviet spacecraft Luna 3 on October 7, 1959. It revealed a curious lack of dark maria on the moon's far side. Later orbiters made possible the production of the Soviet Atlas of the Far Side of the Moon in 1960; and NASA's Lunar Far Side Charts in 1967.
The 6 Apollo missions transported a total of 12 American men to the surface of the Moon, from 1969 to 1972. The astronauts performed experiments in seismic activity, radiation levels, and geologic structure. Hundreds of pounds of lunar soil and rock was returned to Earth, where they are still studied in NASA laboratories. These samples have revealed that the moon contains many minerals similar to Earth, and some that are quite different. We now know that the dark lunar maria are covered with volcanic basalt, and that the light regions are older, heavily cratered highlands. The oldest sample is over 4 billion years old. Study of lunar material gives us clues to the origin of the moon, Earth, and solar system.
The high resolution images gathered by spacecraft have also revealed more lunar features in need of names. Astronauts who visited the moon were quick to name features after their wives and NASA co-workers, but these names were unofficial until recognized by the IAU.
Today, lunar maps are still popular items. Scores of maps and globes, in varying degrees of accuracy, are available for a few dollars. Although our nearest celestial neighbor has revealed some of its secrets to modern scientists, the moon still is an object of fascination and mystery to most of us.