A Field Book of the Stars/Corona Borealis
CORONA BOREALIS (kō-rō'nä bō-rē-a'-lis)—THE NORTHERN CROWN.
Location.—A line drawn from Deneb, in Cygnus, to Vega, in Lyra, and projected a little over 40 degrees, terminates in the Crown, which lies between Hercules and Boötes, and just above the diamond-shaped group of stars in the head of the Serpent. The characteristic semicircle resembling a crown is easily traced out. The principal stars are of the fourth magnitude excepting Gemma, which is a second-magnitude star.
Gemma, sometimes called Alphacca, forms with the stars Seginus and Arcturus, in Boötes, an isosceles triangle, the vertex of which is at Arcturus. A line drawn from Vega in Lyra to Arcturus in Boötes passes through Corona. The star letters in Corona spell "Bagdei."
Note "τ" Coronas, a star that appeared suddenly May 12, 1866, as a second-magnitude star. It was known as the "Blaze Star" and was visible to the naked eye only eight days, fading at that time to a tenth-magnitude star, and then rising to an eighth-magnitude, where it still remains.