Flamsteed number

The Flamsteed number of a celestial object is a combination of number and constellation name (for example, 61 Cygni or 36 Ophiuchi) used to identify naked-eye stars that was adopted by John Flamsteed in his stellar catalogue. The numbers were originally assigned in order of increasing right ascension (west to east) within each constellation, but due to the effects of precession they are now slightly out of order in some places. The designations gained popularity throughout the eighteenth century and are now commonly used when no Bayer designation exists. Not all naked-eye stars in the northern hemisphere have a Flamsteed number and, because Flamsteed's catalogue included only the stars visible from London, most stars in the far southern hemisphere are not covered by the system at all.