Frontpage Alexander's portofolio

Since ten years I observe, draw and photograph the Earth’s only natural satellite, the Moon. This has resulted in many pictures and drawings. The best pictures and drawings are here collected in a book titled ‘An amateur’s Moon: portfolio of lunar drawings and pictures’. The making of this book was in a certain way a necessity to get some order in this archive of lunar material. The observations are collected in the first part of the book. There are no explanations about what is seen on the pictures or about the Moon’s geology because many other excellent books provide this. It is no more (but also no less) than an amateur’s portfolio of lunar drawings and images. All these pictures and drawings were made at the author’s backyard (Brugge, Belgium) or in the nearby Beisbroek Public Observatory.

But because the excellent equipment an amateur can afford nowadays and because of the digital revolution in imaging techniques, more can be done with the observations than simply collecting them in maps. The aim of the second part of the book is to illustrate this briefly. It can be simple but interesting projects like photographing the phases of Moon, imaging its monthly changes, calculating the height of lunar formations or studying the libration zones (Mare Orientale is given as an example). Excellent international programmes like the Bright Lunar Ray Project for the study of lunar rays (Clavius, Mädler and Copernicus are given as an example), and the Selected Area Programme, studying the view of selected lunar formations throughout the lunar day also exist. Recently the Lunar Dome Survey was brought to life again (for instance Mons Rümker). Digital imaging techniques allow even the analyses of the colour of structures bringing this in relation with its geology. These projects, among others, show that lunar science is alive as never before and that amateurs, even with modest equipment, can make valuable observations of our ever interesting celestial neighbour.

‘An amateur’s Moon: portfolio of lunar drawings and pictures’ is downloadeble as a pdf-file, or click on next page to start reading the book in html style.


Frontpage Alexander's portofolio

Introduction – Why Observe the Libration Zones?

You might think that, because the Moon always keeps the same hemisphere turned towards the Earth as a consequence of its captured rotation, we always see the same 50% of the lunar surface. Well, this is not true. Because of the complicated motion of the Moon we can see a little bit around the east and west limb and over the north and south poles. The result is that we can observe 59% of the lunar surface. This extra 9% of lunar soil is called the libration zones because the motion, a gentle wobbling of the Moon in the Earth’s sky responsible for this, is called libration.

In spite of the remainder of the lunar Earth-faced side, observing and even the basic task of identifying formations in the libration zones is not easy. The formations are foreshortened and seen highly edge-on. Obviously, you will need to know when libration favours which part of the lunar limb and how much you can look around the Moon’s limb.

Before the space age, observing the libration zones was a hot issue because it meant observing uncharted territory. Nowadays, these zones have been photographed in great detail, so why observe these difficult regions?

The answer is twofold. First of all, and a little bit of a cliché, it is still a challenge to observe and try to identify the different structures. After all, you’ll get to see a piece of lunar territory not many amateur astronomers and casual lunar observers will ever see.

Secondly, the libration zones harbour some very interesting and unique formations. Observing the lunar libration zones means observing impact basins. This is not surprising since lunar geology is all about impact basins! Some fine and intriguing examples are situated in the libration zones. Take for instance the young Orientale impact basin. If this basin was situated on the near side of the Moon, we certainly would have grasped the concept of impact basins and its meaning for understanding lunar geology much earlier. Otherwise, the Humboldtianum impact basin is intriguing since it has a polygonal shaped outer ring but normal circular inner ring. The Australe, Smythii and Marginis basins are all very old and modified basin. They show us the complex evolution these old basins made from their formation, during the great bombardment up until now. Interestingly, the Smythii basin probably contains one of the oldest and one of the youngest lava sheets observable on the Moon. There is also the impressive Leibnitz Mountains forming the outer rim of the gigantic South Pole-Aitken basin, the largest impact basin in the solar system. The least interesting limbs to observe are the north-western part and the area around the north pole since they consist mainly of craters from which few details can be seen.

This portfolio bundles images of the libration zones and intends to be a guide for observing these regions. The Moon’s limb is therefore divided in seven zones. All images are made with amateur equipment, so everybody can observe what is illustrated here. A limited description of the libration zones and their geology is also given. The equipment used and the libration circumstances for the observations are given in Appendix I. A lunar timescale, to which the age of different structures is referred to, is given in appendix II.

So, get your telescope tuned and check the ephemerides to observe the libration zones!

Why Observe the Libration Zones? is downloadeble as a pdf-file.

avdenboh@yahoo.co.uk