old appellation of d Ophiuchi, and Sigma Telescopii was placed in Corona Australis. Initially uncatalogued, the latter is now known as HR 6875. The original object Lacaille had named Eta Telescopii—the open cluster Messier 7—was in what is now Scorpius, and Gould used the Bayer designation for a magnitude 5 star, which he felt warranted a letter. Characteristics A small constellation, Telescopium is bordered by Sagittarius and Corona Australis to the north, Ara to the west, Pavo to the south, and Indus to the east, cornering on Microscopium to the northeast. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Tel". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a quadrilateral. In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −45.09° and −56.98°. The whole constellation is visible to observers south of latitude 33°N. Features Stars Within the constellation's borders, there are 57 stars brighter than or equal to apparent magnitude 6.5. With a magnitude of 3.5, Alpha Telescopii is the brightest star in the constellation. It is a blue-white subgiant of spectral type B3IV which lies around 250 light-years away. It is radiating nearly 800 times the Sun's luminosity, and is estimated to be 5.2±0.4 times as massive and have 3.3±0.5 times the Sun's radius. Close by Alpha Telescopii are the two blue-white stars sharing the designation of Delta Telescopii. Delta¹ Telescopii is of spectral type B6IV and apparent magnitude 4.9, while Delta² Telescopii is of spectral type B3III and magnitude 5.1. They form an optical double, as the stars are estimated to be around 710 and 1190 light-years away respectively. The faint (magnitude 12.23) Gliese 754, a red dwarf of spectral type M4.5V, is one of the nearest 100 stars to Earth at 19.3 light-years distant. Its eccentric orbit around the Galaxy indicates that it may have originated in the Milky Way's thick disk. At least four of the fifteen stars visible to the unaided eye are orange giants of spectral class K. The second brightest star in the constellation—at apparent magnitude 4.1—is Zeta Telescopii, an orange subgiant of spectral type K1III-IV. Around 1.53 times as massive as the Sun, it shines with 512 times its luminosity. Located 127 light years away from Earth, it has been described as yellow