This is a double constellation composed of Aquila and Antinoüs. Altair is in the neck of the Eagle, Alschain in the head of Antinoüs.
When the moon is absent, a rude arrowhead can be traced out, embracing almost all the stars in Aquila.
η is an interesting variable star, changing from magnitude 3.5 to 4.7 and back again within a period of 7 days 4 hours 12 minutes.
Altair rises about 8° north of the exact eastern point on the horizon.
In A.D. 389 a wonderful temporary star flashed out near Altair that equalled Venus in brightness and vanished within three weeks' time.
DELPHINUS (del-fi´-nus)--THE DOLPHIN, OR JOB'S COFFIN. (Face Southeast.)
LOCATION.--The little cluster of five stars forming Delphinus is to be seen about 10° northeast of Altair, and, though there are no bright stars in the group, it can hardly escape notice. A line drawn from Vega to Albireo, and prolonged about 20°, strikes the star ε in the tail of the Dolphin. The four other stars of prominence in the constellation are a little above ε, and form a diamond-shaped figure.
The little asterisms Sagitta, the Arrow, and Vulpecula and Anser, the Fox and Goose, are shown just above Delphinus.
Delphinus is also called Job's Coffin. The origin of this appellation is unknown.
In Greece, Delphinus was the Sacred Fish, the sky emblem of philanthropy. The Arabs called it the "Riding Camel."
The star γ Delphini is a fine double for a small telescope with a marked and beautiful contrast of colors.
The names for α and β reversed spell "Nicolaus Venator," the Latinized name of the assistant to the astronomer Piazzi.
SAGITTARIUS (saj-i-tā-ri-us)--THE ARCHER. (Face South.)
LOCATION.--A line drawn from Deneb, in Cygnus, to Altair, in Aquila, and prolonged an equal distance, terminates in Sagittarius about 10° east of its distinguishing characteristic, the Milk Dipper. Sagittarius is one of the signs of the zodiac, and lies between Capricornus, on the east, and Scorpius, on the west.
The bow is easily traced out. γ marks the arrow's tip.
Note the star μ, which serves to point out the Winter Solstice, where the solstitial colure intersects the ecliptic.
On a clear night, the pretty cluster known as Corona Australis, the Southern Crown, can be seen about 10° below the bowl of the Milk Dipper. Its lucida, the fourth-magnitude star Alfecca Meridiana culminates at 9 P.M., August 13th.