Charles Piazzi Smyth (January 3, 1819 – February 21, 1900), was Astronomer Royal of Scotland from 1846 to 1888.

He was called Piazzi after his godfather, the Italian astronomer of that name, whose acquaintance his father, Admiral Smyth, had made at Palermo when on the Mediterranean station. His father subsequently settled at Bedford and equipped there anobservatory, at which Piazzi Smyth received his first lessons in astronomy, At the age of sixteen he went out as assistant to Sir Thomas Maclear at the Cape of Good Hope, where he observed Halley's comet and the great comet of 1843 , and took an active part in the verification and extension of La Caille's arc of the meridian .

In 1845 he was appointed Astronomer Royal for Scotland and professor of astronomy in the University of Edinburgh. Here he completed the reduction, and continued the series, of the observations made by his predecessor, Thomas Henderson (see Edinburgh Observations, vols. xi.-xv.). In 1856 he made experimental observations on the Peak of Teneriffe with a view to testing the astronomical advantages of a mountain station. The Admiralty made him a grant of £500 for the purpose, and a yacht--the "Titania" of 540 tons (550 t) and a fine 74 in (1.88 m) equatorial telescope were placed at his disposal by friends.

The upshot of the expedition was to verify Isaac Newton's surmise, that "a most serene and quiet air ... may perhaps be found on the tops of the highest mountains above the grosser clouds." The scientific results were detailed in a Report addressed to the lords commissioners of the admiralty, 1858, in a communication to the Royal Society (Phil. Trans. cxlviii. 465) and in the Edinburgh Observations, vol. xii. A popular account of the voyage is contained in Teneriffe, an Astronomers Experiment, 1858.

In 1871-1872 Piazzi Smyth investigated the spectra of the aurora, and zodiacal light. He recommended the use of the rain-band for weather prediction (Jour. Scottish Meteor. Society, v. 84), and discovered, in conjunction with Professor AS Herschel, the harmonic relation between the rays emitted by carbon monoxide. In 1877-1878 he constructed at Lisbon a map of the solar spectrum (Edin. Phil. Trans. xxix. 285), for which he received the Macdougall-Brisbane prize in 1880.

He researched wet collodion process photography and infrared astronomy, and was notable for advancing the theory (in his book Our Inheritance in the Great Pyramid) that the Great Pyramid of Giza was a repository of prophesies which could be revealed by detailed measurements of the structure.

Further spectroscopic researches were carried out by him at Madeira in 1880 (Madeira Spectroscopic, 1882), and at Winchester in 1884 (Edin. Phil. Trans. vol. xxxii. pt. ii.). He published besides Three Cities in Russia, (1862), Our Inheritance in the Great Pyramid (1864), Life and Work at the Great Pyramid (1867), and a volume On the Antiquity of Intellectual Man (1868). In 1888 he resigned his official position and retired to the neighborhood of Ripon, where he remained till his death.

See Month. Notices Roy. Astr. Society, lxi. 189; Observatory, xxiii. 145, 184; R Copeland in Astr. Nach. No. 3636, and Pop. Astronomy (1900), p. 384; Nature, lxii. I 61 (AS Herschel); André and Rayet, L'Astronomie pratique, ii. 12.