John Flamsteed was an English astronomer and the first Astronomer Royal. He catalogued over 3,000 stars.

The second system that uses the constellations in which the stars reside is the Flamsteed system.

The Bayer system was useful for naming the stars—certainly better than using common names—but it had problems. The first was that of fluctuating brightness, as in the case of Betelgeuse and Rigel. The second problem was that there are only so many letters in the Greek alphabet.

Unlike the Bayer system, the Flamsteed system can be used to name an unlimited number of stars. In this system, we still use the Latin possessive name of a star's constellation, but this time the stars are distinguished not by their brightness, but also by their proximity to the western edge of their constellations.

The star closest to the western edge is assigned the number 1; the second-closest star to the western edge is number 2, and so on.

For example, the star Sirius is called Alpha Canis Majoris in the Bayer system and 9 Canis Majoris in the Flamsteed system, meaning that it is the ninth-closest star to the western edge of the constellation Canis Major.