Moongazing: Beginner’s guide to exploring the Moon. Royal Greenwich Observatory

can be seen, having the appearance of a small lunar sea in its own right. Byrgius crater, a popular sight, is to the south of Grimaldi.

       North-West

       North-West

      The north-western quadrant of the Moon is home to prominent craters such as Kepler, Copernicus and Plato, as well as Aristarchus, the brightest crater on the entire surface. The bright craters and dark plains of Oceanus Procellarum and Mare Imbrium (Sea of Showers) make this one of the most striking, high-contrast regions of the Moon. Nestled in the western edge of Mare Imbrium is Sinus Iridum (Bay of Rainbows.)

History of Lunar Observation

      The Moon has lingered in our skies as long as life has existed on Earth. It predates the earliest murmurings of consciousness by billions of years. When our ancestors began to take notice of the objects in the sky, the Moon was already a familiar sight, whose regular visits were probably a source of comfort, providing a source of natural light at night. But as the earliest humans attempted to explain the world around them, events in the sky became steeped in superstition. Then unpredictable, aberrant changes in the appearance of the Moon, such as eclipses, terrified ancient people as harbingers of doom. Today we flock to see them and enjoy the spectacle.

      Eventually this perception of the Moon as a god of many moods began to fade, when as early as the fifth century BCE, astronomers in ancient Babylon learned to predict its eclipse cycle through careful record-keeping across generations. Meanwhile, in Asia, astronomers in what is now modern-day India worked out how to describe the apparent elongation between the Moon and Sun throughout the full synodic month.

       The Mesopotamian god of the Moon, Sin, depicted on a tablet at the British Museum.

      A great deal of progress was made when mathematical cosmologies – descriptions of what we now call the Solar System, but what was once considered to be the centre of the Universe – were developed in ancient Greece. Notably, Aristarchus in the second century BCE, considering the Moon as a spherical ball of earth or rock, computed its size and distance. His results weren’t precise, but they were certainly better than anything that had been achieved before. In the same century, Seleucus had correctly linked the Moon to the tides, long before Newton would describe the force responsible.

      A few hundred years later, Ptolemy significantly improved on previous calculations about the size and distance of the Moon, but with the transition to the Middle Ages, this progress of understanding slowed down.

      The next leap in lunar observation would occur with the invention of the telescope in the early seventeenth century. Skilled observers of the pre-telescopic era, such as Tycho Brahe, had attempted to discern the Moon’s surface, but even the best of their visual acuity was no match for the telescope. Many people incorrectly believe that Galileo Galilei pioneered the use of the telescope in astronomy, but he was actually beaten to it by Thomas Harriot, an English scientist then living in London. Harriot was credited with making the first sketch of the Moon with the aid of a telescope in July 1609, approximately four months before Galileo’s first use of such an instrument. Nevertheless, Galileo was the first to make a systematic study of the sky using the telescope, and in the following year published his ground-breaking Sidereus Nuncius (Starry Messenger), including sketches of the Moon, showing unprecedented detail.

      Over the next 400 years, rapid improvements in telescope technology would greatly improve our perception of the lunar surface. Generations of skilled observers discovered and catalogued features large and small, attempting to explain their origin. The Moon became the subject of the very first successful astronomical photograph, which was a daguerreotype captured by John Draper in 1840.