Observation 
Observing the MoonMoon is sometimes pleasantly introduced like the nearest celestial body to Earth. More simply, Moon is a fine object for an amateur to look at and to observe. Each month, Moon is appearing as a fine crescent on the western horizon soon after new moon. Moon increases then into a full quarter, and reaches full. At that moment, it is rising on the eastern horizon at the moment when Sun sets West. Moon eventually wanes down, through another quarter, to a mere last crescent. It then is rising few before Sun. All along its track in the sky, Moon is always providing observers with fine moments. Useful additional elements may be found at our Moon's Phases tutorial in terms of celestial mechanics
 | the Moon is an inspiring object in terms of observation. picture site 'Amateur Astronomy' |
Main observational trick about Moon is to observe lunar features when they are near what is termed the "terminator". Terminator is where the lighted parts of Moon are separated of the parts still in the dark by Sun's light. When Moon is waxing or waning Sun's light is grazing the Moon's surface along the terminator, enhancing the landscape's appearance. Some features -albeit rarer- are best seen at full moon however like the rays systems emanating from some craters. Lunar features mainly sort into maria, hills and mountains, and craters. Aristotle's views which only admitted perfect celestial bodies, lunar features were just seen like the reflection of the Earth or even clouds condensed or emanating from the Earth as such views kept until the science revolution of Modern Times. The term 'lunar maria' was invented by the Roman writer Plutarch (46-125 A.D.) who saw the Moon like a other Earth as the dark areas were seen like seas and highlands like lands. Maria are mostly basalt flows which flooded lunar surface due to meteoritic shocks, as the near side Moon crust seems to have thinner than the far side one. maria may be dated 3.8-3.1 billion years old. Hills and mountains are ancient highlands dating back to about 4 billion years (which should be of the same age too on the far side, which is mostly highlands and craters, and devoided of maria). Craters were created by various impactors all along Moon's life. Such a bombardment began 4.6 billion years ago. Latest and polemical theory about Moon's origin is that it formed from a large impactor hitting Earth, ejecting material in orbit. This material eventually accreted into Moon. A good idea as far Full Moon is concerned, in terms of observation is, when season and sky luminosity permitting, to observe it when the background sky is still for early, to twilight. That provides for a lesser brightness of the Moon and the possibility to observe varied lunar features under a Full Moon light more accurately, and withouht the hindrance of a Moon too bright! When the sky is darkening then, the observation becomes less easy as most observable regions are now those close to the limb which harbours the terminator only. On the other side, a observation is possible too at the condition to mask the larger part of Moon's disk outside the field of view however! At a low magnification, a method to dampen Moon's glare, when, for example, observing terminator regions few before, or after the Full Moon, is to decrease the telescope aperture. This is usually done through the cap of it, which may be provided with such a concept, the main cap being let in place and a smaller cap opened to let light in through a smaller hole. Of note is that the Moon is findable in the daylight sky from around the First Quarter to waxing gibbous as that is also the case from the waning gibbous Moon to around the Last Quarter. The only difference is that the Moon is seeable in the afternoon, and then by the morning, respectively
The time in days counted from the time of new moon is called the Moon's age as the concept of "percentage of Moon's surface illuminated" is the ratio of the area of Moon's near side illuminated to the total area, multiplied by 100. This value starts at 0 percent at the moment of the new moon to reach 100 percent at full moon, via the first quarter. Then the opposite, back to new moon. Technically, as far as phases are concerned, the four primary phases (new moon, first quarter, full moon, last quarter) are when the ecliptic longitude of the Moon (where it is along the ecliptic) is differing from that of Sun by 0, 90, 180, and 270° respectively. for more about Moon rotation, orbit, phases, see the tutorial "Moon's Phases"
Another remarkable Moon feature is the one due to what is termed "libration". Although Moon is always turning the same face to us, we are allowed to see about 59 percent of its surface in total. This is due to the fact that Moon' orbit is an ellipse, with a point nearest (perigee, from the Greek "peri", "near", and "geos", "Earth") and a point farthest (apogee) Earth. The Moon is speeding on its orbit at the perigee and slowing at the apogee as its rotation rate is remaining the same. Hence we see a little more than a strictly 100 percent near side, some percentage each side of it. Moon eastern and western parts but northern and southern are concerned too by a libration phenomenon, albeit less. This one is due to the Moon axis' tilt. Libration makes possible to see features usually out of reach. A well-known exemple are regions beyond Mare Crisium on the eastern limb or the famed Mare Orientale, beyond Grimaldi Crater. At last due to the perigee/apogee concept, Moon at the perigee (nearest Earth) has a larger apparent diameter, and a smaller one at the apogee (farthest Earth). This is not of great importance for observation however, albeit some are waiting for the most favorable perigees to make astrophotography at Moon. At the apogee Moon is 26,000 miles farther than at the perigee, which translates in a difference in apparent diameter of about 2.5' wide in average. Some perigees coinciding with a Full Moon however -which occurs about once or twice a year- may bring a Moon larger by a 14 percent of apparent diameter and 30 percent in brightness, sometimes dubbed like a 'supermoon' by some medias. At last, note that, as Earth itself has a nearest (perihelion; in January each year) and a farthest (aphelion; July) point from Sun, this means that, each year in winter, Moon is somehow brighter as it's nearest Sun altogether with Earth as it's dimmer during summer. The addition of perihelion/aphelion (Earth) and perigee/apogee (Moon) values makes that moonlight at full moon is varying by about 15 percent each side of an average value. Although this seems high, it mostly goes unnoticed as we have no point of reference when looking at Moon at such or such period of the year. 'Transient lunar phenomena' are short-lived phenomena occurring on the face of the Moon. They have been witnessed for at least a thousand years as they result of impacting meteoroids
Any of the about twelve moons in a year have got a surname in the U.S.A, like the first full moon of the year being the 'wolf moon', dating to the time of Native Americans when hungry wolves howled at the full moon on cold winter nights. By the turn of the 18th century A.D. English astronomers had deviced two Full Moon of note: the 'Harvest Moon,' the Full Moon nearest to the fall's equinox as then the light of the rising Moon may immediately succede to the sunset and give the feeling that daylight is keeping on (such a occurrence is now scheduled to occur by 2029 only). By that same era, astronomers also deviced the 'Hunter's Moon,' the second Full Moon after the fall's equinox, which may display the same simultaneity with sunset. The term 'Blue Moon' refers to the second Full Moon in a given month. As far as the popular theme of the so-called 'moon illusion' is concerned, the moon just tends to look bigger when seen near the horizon, as this is just an illusion. Astronomers and psychologists however don't agree on how to explain it. As a Full Moon, on another hand, has, except in the case of a Moon eclipse, never a perfect alignment with the Earth and the Sun, the Moon, during a Full Moon is actually slightly less than 100 percent illuminated. For a given month, generally, whatever the latitude or the season, one must take in account that, by 10:30 p.m. local time, about 17-18 days are hampered in terms of deep sky observation by the presence of Moon. A black moon is a additional new moon that appears in a month, or the absence of a full moon. A second new moon of the month typically occurs about once every 29 months
 | shadows casted by lunar mountain ranges and peaks allowed for the calculation of their age before the space age (region in Sinus Medii as seen by the Apollo 10 mission). picture courtesy NASA |
Moon light does not need as much cares as does Sun's but some people may find it harming, especially at a high power -or a high power and a Full Moon. No dedicated Moon filter exists at the exception of neutral grey ones and a polarizing filter (which may be double). Both types, generally, procures a more comfortable observation as neutral filter may provide some more accurate details and polarizing filter may be helpful to Moon astrophotography
Moon is fine to view in various instruments. Binoculars are already providing a general view of the Moon, helping to learn landscape main features like the main seas, main craters, and highlands. Small, beginners instruments provide fine regional views for exploration, as the high end of that range, like a 4' ½ reflector will already provide for large possibilities of observation, shortening the field of view. Largest powers with such telescope, like 120x or 150x, mostly are used to check a view only. Larger instruments still transform the Moon into a lifelong exploration field! They allow for fine detailed views and photographs. Most of lunar observation practitioners stress that drawing sketches of what one observes is training and deepening one observer's skills. Moon may be observed naked-eye too, as Moon is a fine and easy object for astrophotography
