Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in (see 88 modern constellations for a list of constellations and the genitive forms of their names). Flamsteed designations were assigned to 2554 stars.
The numbers were originally assigned in order of increasing right ascension within each constellation, but due to the effects of precession they are now slightly out of order in some places. This method of designating stars first appeared in a preliminary version of John Flamsteed's Historia Coelestis Britannica published by Edmond Halley and Isaac Newton in 1712 without Flamsteed's approval. The final version of Flamsteed's catalogue published in 1725 after his death omitted the numerical designations altogether.
Flamsteed designations gained popularity throughout the eighteenth century, and are now commonly used when no Bayer designation exists. Where a Bayer designation does exist for a star, it is usually used in preference to the Flamsteed designation. Examples of well-known stars that are usually referred to by their Flamsteed numbers include 51 Pegasi, and 61 Cygni. Flamsteed designations are often used instead of the Bayer designation if the latter contains an extra attached number; for example, "55 Cancri" is more common than "Rho-1 Cancri".
There are examples of stars, such as 10 Ursae Majoris in Lynx, bearing Flamsteed designations for constellations in which they do not lie, just as there are for Bayer designations, because of the compromises that had to be made when the modern constellation boundaries were drawn up.
Flamsteed's catalogue covered only the stars visible from Great Britain, and therefore stars of the far southern constellations have no Flamsteed numbers. Some stars, such as the nearby star 82 Eridani, were named in a major southern-hemisphere catalog called Uranometria Argentina, by Benjamin Gould; these are Gould numbers, rather than Flamsteed numbers, and should be differentiated with a G, as in 82 G. Eridani. Except for a handful of cases, Gould numbers are not in common use.
List of constellations using Flamsteed star designations
There are 52 constellations that primarily use Flamsteed designations. Stars are listed in the appropriate lists for the constellation, as follows:
- Canes Venatici
- Canis Major
- Canis Minor
- Coma Berenices
- Corona Borealis
- Leo Minor
- Piscis Austrinus
- Ursa Major
- Ursa Minor
- "Naming Astronomical Objects". International Astronomical Union (IAU). Retrieved 2009-01-30.
- "Naming Stars". Students for the Exploration and Development of Space (SEDS). Retrieved 2009-01-30.