A catalogue of the positions of 4,243 stars in the region of the north celestial pole, by S. Groombridge, published in London in 1838.

A small southern constellation, introduced probably by sixteenth-century navigators and included by Johann Bayer in his atlas Uranometria, published in 1603. It contains four stars brighter than fourth magnitude. Delta Gruis δ Gru is a double star that can be split by the unaided eye.

Abbreviation for Greenwich Sidereal Time.

The two stars β Beta and γ Gamma in the constellation Ursa Minor.

An expression used by Chinese astronomers in historical times to denote the appearance of a nova, supernova or comet.

A star on which the manual or automatic guidance system of a telescope can be locked in order to ensure that some fainter object being observed is correctly followed as the Earth rotates.

A catalogue of 18,819,291 celestial objects created as the database for operations of the Hubble Space Telescope. Including 15 million stars and over three million galaxies, this is the largest catalogue of celestial objects ever produced.

A telescope on the same mounting as one being used for photography or with instruments, provided for the purpose of guiding the telescope accurately during the course of an observation.

A large, circular emission nebula in the southern constellations Vela and Puppis, discovered by an Australian astronomer, Colin Gum. The nebula is 30° across, which is equivalent to a diameter of 800 light years at its distance of 1,300 light years. It is thought to be the result of ionization of the interstellar medium caused by a supernova that exploded perhaps a million years ago. This would mean that there is no longer a source of energy, and the nebula is now gradually fading as ionized hydrogen recombines and ceases to be luminous.

Abbreviation for Grand Unified Theory.