This part of The Cambridge Star Atlas consists of six all-sky maps to show the general distribution of different objects in the sky. Each of the six maps shows the whole sky in a so-called ‘equal-area’ projection; the Mollweide projection, named after the man who invented it.

It's obvious that you cannot show the inside of the whole celestial sphere on a simple flat map, without severe distortion. There are many different projections that can be used to create an all-sky map (or a map showing the whole surface of the Earth), and every projection has its advantages and disadvantages. Mollweide's is an ‘equal-area’ projection, meaning that in spite of the inevitable distortion the actual area covered by one square degree remains the same, no matter where on the map it is measured. So the distribution, or density of objects, is not influenced by the map's projection. Since that is the goal of these maps, the disadvantage, that the shapes of the constellations near the edges are extremely distorted, is taken for granted. If the constellation lines were not drawn, it would be hard to recognize them!

Unlike the main star charts, these maps are presented in galactic coordinates. The Galactic Equator is the central, horizontal line, marked 0°. On the main star charts it is represented as the blue dashed line, making an angle of almost 63° with the Celestial Equator.