MAN ON THE MOON July 20, 1969 is a very important date in the history of mankind. It was20:56:31 at Houston, Texas when the first man, the American astronautNeil Armstrong, set his foot on the Moon, in a region of MareTranquillitatis. This historical event began eight years before, when, on May 25, 1961,the President of the United States of America, John Fitzgerald Kennedy,in a historical speech to the Congress asked for the nation's help tomake possible the most important and risky undertaking that man had yetdone. He said: "... I believe that this Nation should commit itself toachieving the goal, before this decade is out, of landing a man on theMoon and returning him safely to the Earth.". To achieve this result NASA scientists designed and built the biggestand most powerful rocket in history. It was 110 meters tall and itsweight at lift-off was 2817 metric tons. Its name: Saturn V. At the top there is a cone three meters wide and three meters tall: theApollo spacecraft. And in one of these spacecrafts, named Apollo 11, onJuly 16, 1969, at 09:32, from the launching pad 39A at Cape Canaveral,the historical flight of Neil Armstrong, Edwin Aldrin and MichaelCollins began, a flight that would be over 195 hours later in thePacific Ocean. THE INTERIOR OF THE MOON The Moon has a spheroidal shape with a diameter of nearly 3500 Km and anaverage density of 3.34. Thus the Moon is lighter than Earth bothbecause of the different size and from the point of view of the density.A cubic centimeter of lunar rock weighs 3.34 g; the same amount of rockfrom the Earth weighs 5.5 g. These are average values. The Moon is not homogeneous throughout itsvolume: the density increases going towards the center. The crust of the Moon is composed of silicates down to the depth ofabout 50 km. Under this crust we have, like in the Earth, a mantlecomposed by metamorphic rock and other elements of medium density. Downto 1000 km below the lunar surface we can find the heavy elements, likeiron and nickel, forming the lunar core. CHARACTERISTICS OF THE LUNAR SURFACE To the naked eye a superficial look at the full Moon will show a whitishdisk with greyish stains and dark spots. The shape of these patternsreminds people with a vivid imagination of a human face, the well known~man on the Moon~. Others, less numerous, compared it with a mancarrying a bundle of firewood, with a woman reading a book and with theoutline of a woman kissing someone! Other imaginary shapes are the craband the rabbit. A small telescope or a binocular show that these greyish areas arestrewed with spots, stains and bright stripes with vivaciously colouredbelts. An evident characteristic of the Moon is the set of brightstripes radiating from a single point near the southern border. A lessspectacular set of radial belts is inside a dark area near the easternborder. The general view of the full Moon through a telescope is rather uniform;it looks like a map without relief and everything is dazzling white.This happens because the Sun is shining just in front of the Moon andits light is diffused directly towards our eyes. In other phases thesunlight is oblique and enhances the visibility of the irregularfeatures of the lunar surface. Very evident shadows can be seen, inparticular near the "terminator", where the Sun is rising or setting andthe angle of illumination is very oblique. The lightest belts are themost uneven; the darkest belts are sufficiently flat. Through a smalltelescope, the main characteristic that may be seen are the innumerableformations with the shape of a ring generally called "craters", spreadover the whole lunar surface. They are very numerous in the brightregions where some of them overlap older ones, while in the dark areasthey are much more sparse. Observing the areas near the terminator, theshadows towards the interior of the craters and the lava flows neartheir raised boundaries give the impression of very deep depressions.This is an illusion caused by the very oblique illumination: cratersare, in reality, shaped like shallow bowls. There is a large variety of dimensions, starting from large "enclosures"with a diameter greater than 200 km down to holes under the resolvingpower of the largest terrestrial telescopes, as we can see in close-uppictures taken by lunar probes. APPEARANCES AND DISAPPEARANCES Cassini Although not seriously cited as an example of a "new" crater on theMoon, it is however strange that the Cassini crater had been omittedfrom older lunar maps. It appeared for the first time in the map byD.J.Cassini in 1692, and was therefore named after him. The Cassinicrater is a very evident formation during phases of grazingillumination, but it is nearly invisible during the other phases;probably because of this it was not included in the old maps. Thus it isnot a real "new" crater. New craters in Halley The darkening seems to be the cause of this strange phenomenon: theappearance of a new small crater on the floor of crater Halley, whenLewis Rutherford photographed it in 1865. Lohrmann and Madler did notshow details on the floor of Halley, but in Rutherford's photo a crateris very evident. This is not sufficient evidence for the formation of anew crater, but it is interesting that today there are two craters onthe floor of Halley. There is a second crater not showing inRutherford's photo and it can be a new one. However it is possible thatsomething was darkening it while it was photographed. DRAWING THE MOON Observing the Moon, even without strictly scientific purposes, can be aninteresting activity for the amateur astronomer with cheap instruments:1) For a detailed study of the lunar surface there is no need ofexpensive instruments with large apertures; even the classical 60 mmrefractor can be good enough, if the seeing is good. Obviously, largerapertures can produce more detailed images; with these instruments theobserver can notice finer details. Furthermore, for lunar observation refractors are better than reflectorswith the same aperture. 2) A very interesting activity is represented by the observation ofchanges in details of the lunar surface because of different lightconditions. Craters which look spectacular with grazing light becomenearly unrecognizable at local midday. A continuative study withdrawings and notes on specific lunar characteristics can be very usefulin understanding the actual vertical profile of the observed details. 3) Observing and drawing lunar characteristics is certainly useful as anexercise for the eye. The practice achieved may be useful when theobserver will devote himself to other plans like solar and planetaryobservations. 4) To obtain a photograph reproducing details visible by directobservation with a 200 mm telescope, a 300/350 mm instrument isrequired. Thus, visual observers that draw what they see at theeyepiece make the most of their telescopes. Here is some advice about lunar observation for those who wish to startthis activity: a) At first draw only the evident details, then add the smaller ones. b) Draw only small regions of the lunar surface, especially if theseeing is good and if there are a lot of significant details. c) If you have to observe a formation near the terminator at the localsunrise, details near the shadow must be drawn at the end. Instead,observing a formation near the terminator at the local sunset, detailsnear the terminator must be drawn at the beginning. d) Make a first drawing directly at the eyepiece, then complete thissketch at home immediatly after the observation, without changing anydetail already drawn. e) Add to the drawing the following information: I) name of the observed formation; II) year, month and day of the observation; III) time of the beginning and of the end of the observation in U.T.; IV) seeing (expressed with a number between 1 and 5: 1 = good, 5 = poor); V) selenographic colongitude at the time of half observation, i.e. the lunar longitude of the terminator at the time of half observation; VI) instrument and magnification used; VII) observer's name and location; VIII) any other useful note.
