Delphinus one of the smallest constellations, located east of Aquila and west of Aquarius. It is . It appears as a slightly flattened diamond or kite, with a few fainter stars as a tail. Delphinus is best seen July through November.
History and MythologyDelphinus was recorded by Ptolemy in the 2nd century AD. The dolphin was placed in the sky by Poseidon, god of the sea, in gratitude for helping him woo and win the mermaid Amphitrite. Other legends tell us that Delphinus was the son of the sea god Triton, who saved the life of the poet and harpist Arion.
Notable Objects
Alpha and Beta Delphini have the unusual names Sualocin and Rotanev. These originate from the Palermo star catalogue of 1814, and are the reversed Latinized name of the astronomer Nicolaus Venator who inserted them into the catalog as a practical joke. While nearby in the sky and tied by name, Sualocin is 2.5 times farther away than Rotanev, which lies at a distance of 97 light years.
Gamma Delphini is an interesting double star, consisting of a magnitude 4.5 and 5.5 components separated by 10 arcseconds. The fainter star appears somewhat greenish.
There are two globular clusters in Delphinus. NGC 6934 is a 9th magnitude globular cluster at a distance of 51,000 light-years. NGC 7006 is one of most remote clusters at a distance of 135,000 light-years, which puts it far from the plane of the Milky Way. For a good view, both clusters require an 8 inch or larger telescope.
NGC 6891 is a 10th magnitude planetary nebula which appears somewhat bluish in color. NGC 6905 is a large but faint planetary on the northwest corner of Delphinus. Both nebulae require a 12 inch or larger telescope.