Delphinus

Delphinus lacks stars above fourth (apparent) magnitude; its brightest star is of magnitude 3.8. The main asterism in Delphinus is Job's Coffin, nearly a 45°-apex lozenge diamond of the four brightest stars: Alpha, Beta, Gamma, and Delta Delphini. Delphinus is in a rich Milky Way star field. Alpha and Beta Delphini have 19th century names Sualocin and Rotanev, read backwards: Nicolaus Venator, the Latinized name of a Palermo Observatory director, Niccolò Cacciatore (d. 1841).[1]

Alpha Delphini is a blue-white hued main sequence star of magnitude 3.8, 241 light-years from Earth.

Beta Delphini, called Rotanev. The gap between its close binary stars is visible from large amateur telescopes. To the unaided eye, it appears to be a white star of magnitude 3.6. It has a period of 27 years and is 97 light-years from Earth.

Gamma Delphini is a celebrated binary star among amateur astronomers. The primary is orange-gold of magnitude 4.3; the secondary is a light yellow star of magnitude 5.1. The pair form a true binary with an estimated orbital period of over 3,000 years. 125 light-years away, the two components are visible in a small amateur telescope.[1] The secondary, also described as green, is 10 arcseconds from the primary. Struve 2725, called the "Ghost Double", is a pair that appears similar but dimmer. Its components of magnitudes 7.6 and 8.4 are separated by 6 arcseconds and are 15 arcminutes from Gamma Delphini itself.[2]

Delta Delphini is a type A7 IIIp star of magnitude 4.43.

Epsilon Delphini, Deneb Dulfim (lit. "tail [of the] Dolphin"), or Aldulfin, is a star of stellar class B6 III and magnitude 4, at 330 ly.[3]

In Delphinus, in extremes of distance, Gliese 795 is the closest known star at 54.95 ly and rapidly moves east over a period of centuries (863±3 arcseconds per year); whereas the giant of blue colour, W Delphini is at 2203.81 ly at 9.76 magnitude.[3] Its brightness ranges from a magnitude of 12.3 to a magnitude of 9.7 over its variable period as it is a Beta Persei star-type semi-detached system. Other variable stars of large amateur telescopic visibility include R Delphini, a Mira-type variable star with a period of 285.5 days. Its magnitude ranges between a maximum 7.6 and a minimum 13.8.

Rho Aquilae at magnitude 4.94 is at about 150 light years.[4] Due to its proper motion it has been in the (round-figure parameter) bounds of the constellation since 1992.

HR Delphini was a nova that brightened to magnitude 3.5 in December 1967.[5] A nova was discovered by amateur astronomer Koichi Itagaki, Nova Delphini 2013.[6][7][8]

Giants

Giants within our galaxy in Delphinus aside from Delta, Gamma and Epsilon include:[3]

Its rich Milky Way star field means many modestly deep-sky objects. NGC 6891 is a planetary nebula of magnitude 10.5; another is NGC 6905 or the Blue Flash nebula. NGC 6934 is a globular cluster of magnitude 9.75. At a distance of about 185,000 light-years, the globular cluster NGC 7006 is at the outer reaches of the galaxy. It is also fairly dim at magnitude 11.5.