As seen from Chart 3.1, the Messier Objects are not evenly distributed throughout the sky. A large concentration of galaxies appears in the constellation Virgo, and across the border in the small constellation Coma Berenices. Another group of Objects, consisting mostly of open and globular star clusters, resides in Sagittarius. Meanwhile, a few areas in the sky contain no Messier Objects, notably near the Great Square of Pegasus, but also between Ursa Major and Gemini.

As the sun travels through the sky each year on the ecliptic (see Chart 3.1), the adjacent portions of the sky are not easily visible from the Earth because they rise and set with the sun. For example, when the sun is ‘in’ Gemini, as it is during early July, then it is located in front of the stars that form the constellation that we call Gemini. The stars of Gemini rise at the same time as the sun does. And, as even the non-astronomer notices, the sky brightens for at least an hour before sunrise, making observation of these stars increasingly difficult as dawn advances. Therefore the stars that rise shortly before Gemini are invisible as well. At the end of the day, Gemini sets with the sun.