It is necessary, in the first place, to have some way of designating the stars in each constellation. Many of the brighter stars have proper names as Sirius, Arcturus, and Vega; but the great majority of them are marked by the letters of the Greek alphabet. The brightest star in each constellation is called α (alpha); the next brightest, β (beta); the next, γ (gamma); and so on. The characters and names of the Greek alphabet are as follows:

α,Alpha.
β,Beta.
γ,Gamma.
δ,Delta.
ε,Epsilon.
ζ,Zeta.
η,Eta.
θ,Theta.
ι,Iota.
κ,Kappa.
λ,Lambda.
μ,Mu.
ν,Nu.
ξ,Xi.
ο,Omicron.
π,Pi.
ρ,Rho.
σ,Sigma.
τ,Tau.
υ,Upsilon.
φ,Phi.
χ,Chi.
ψ,Psi.
ω,Omega.

These letters are followed by the Latin name of the constellation. Thus Aldebaran is called α Tauri; Rigel, β Orionis; Sirius, α Canis Majoris.

If there are more stars in a constellation than can be named from the Greek alphabet, the Roman alphabet is used in the same way; and when both alphabets are exhausted, numbers are used.

Circumpolar Constellations. One of the most important constellations, and one easily recognized, is the Great Bear, or Ursa Major. It is represented in [Plate 1] on the Star Chart. It may be known by the seven stars forming “the Dipper.” The Bear’s feet are marked by three pairs of stars. These and the star in the nose can be readily found by means of the lines drawn on the chart. It may be remarked here, that in all cases the stars thus connected by lines are the leading stars of the constellation. The stars α and β are called the Pointers. If a line be drawn from β to α, and prolonged about five times the distance between them, it will pass near an isolated star of the second magnitude known as the Pole Star, or Polaris. This is the brightest star in the Little Bear, or Ursa Minor ([Plate 2]). It is in the end of the handle of a second “dipper,” smaller than the one in the Great Bear.

On the opposite side of the Pole Star from the Great Bear, and at about the same distance, is another conspicuous constellation, called Cassiopeia. Its five brightest stars form an irregular W, opening towards the Pole Star ([Plate 2]).

About half-way between the two Dippers three stars of the third magnitude will be seen, the only stars at all prominent in that neighborhood. These belong to Draco, or the Dragon. The chart will show that the other stars in the body of the monster form an irregular curve around the Little Bear, while the head is marked by four stars arranged in a trapezium. Two of these stars, β and γ, are quite bright. A little less than half-way from Cassiopeia to the head of the Dragon is a constellation known as Cepheus, five stars of which form an irregular K.

These five constellations never set in our latitude, and are called circumpolar constellations.

Constellations Visible in September. At this time the Great Bear will be low down in the northwest, and the Dragon’s head nearly in the zenith. If we draw a line from ζ to η of the Great Bear and prolong it, we shall find that it will pass near a reddish star of the first magnitude. This star is called Arcturus, or α Boötis, since it is the brightest star in the constellation Boötes. Of its other conspicuous stars, four form a cross. These and the remaining stars of the constellation can be readily traced with the aid of [Plate 3].

Near the Dragon’s head ([Plate 4]) may be seen a very bright star of the first magnitude, shining with a pure white light. This star is Vega, or α Lyræ.