Frank McClean, civil engineer, astronomer and educational benefactor, was the son of the civil engineer John Robinson McClean. He studied first at Glasgow University and continued his studies at Trinity College, Cambridge, from 1855, graduating as Bachelor of Arts (BA) in 1859 and Master of Arts (MA) four years later. He became a member of the Institution of Civil Engineers (MICE) and in 1859 was employed on drainage work in the Fen districts. In 1862 he was made a partner in his father's civil engineering firm, McClean & Stileman. Eight years later he acquired a considerable amount of money and was able to withdraw from his profession. Thereafter he devoted himself to collecting books and other cultural artefacts, and scientific pursuits, mainly in astronomy.
McClean completed an astronomical observatory at his home near Tunbridge Wells in 1875 and in 1884 built a laboratory and heliostat nearby. He became a member of the Royal Astronomical Society in 1877 and served on its council from 1891 to his death. Papers and photographic atlases based on his work in astronomical spectroscopy were published in the society's Monthly Notices from 1887 onwards. These publications contained large-scale solar spectra and laboratory spectra, including those of a range of rare metals, to aid line identification. Examples of his papers are "Comparative photographic spectra of the high sun and the low sun..." (1889-1891), and "Photographs of the spectrum of Nova Persei" (1905). Shortly after H.C. Vogel, McClean identified stars with neutral Helium absorption lines and concluded that they were early in the stellar evolutionary sequence. He was furthermore the first to note the association of these stars (that is, stars of spectral type B) with regions of gaseous nebulae.
In a letter dated 10 August 1894 to Dr David Gill*, director of the Royal Observatory, Cape of Good Hope, McClean offered to finance a large telescope and spectroscope, complete with building and dome, to be erected at the Cape. The detailed design of the instrument and its building was worked out by McClean and Gill during 1895. It comprised a 600 mm photographic refractor with a twin 450 mm visual refractor, fitted with a slit spectroscope and object-glass prism, and was the first large telescope to be erected in southern Africa. The equatorial mounting and object glasses arrived in April 1898, with additional equipment following during the rest of the year. After various delays and modifications, including the return of the main object glass to the manufacturer to correct faults, the instrument was eventually completed in 1901. It was officially named the Victoria telescope, but is commonly known as "the McClean".
Meanwhile, in 1895, McClean had installed a twin 300/250 mm Grub photovisual refractor in his own observatory and became a pioneer of objective prism spectroscopy. His large prism yielded a single wide-dispersion spectrum per plate of each star brighter than magnitude 3.5 in the field of view. He used the instrument during 1895 and 1896 to conduct a systematic spectroscopic survey of the brighter stars in the northern hemisphere. The results were published as "Comparative photographic spectra of stars to the 3.5 magnitude" in the Philosophical Transactions of the Royal Society (1898, Vol. 191, pp. 127-138). In 1897 he accepted an invitation by Gill to bring his prism to the Cape observatory and extend his survey to the whole sky. His objective prism was mounted on the observatory's astro-photographic telescope and from June to September 1897 he recorded the spectra of 116 bright stars that could not be seen from Tunbridge Wells. His wife and daughter joined him at the Cape. He departed for England towards the end of October. The results of his visit, including the discovery of oxygen in the spectrum of beta Crucis, were published in Spectra of southern stars (London, 1898), as well as in the Proceedings of the Royal Society (1898, Vol. 62, pp. 417-423). The survey earned him the gold medal of the Royal Astronomical Society in 1899. Around this time his health began to fail and he was unable to return to the Cape to see the telescope he had donated.
McClean was awarded an honorary Doctor of Laws (LLD) degree by Glasgow University in 1894 and the next year was elected a Fellow of the Royal Society. He was a founding member of the British Astronomical Association and served on its council from 1900 to 1902. In 1890 he founded three Isaac Newton studentships in astronomy and physical optics at the University of Cambridge, and left large sums of money to the University of Birmingham and Newall Observatory. His collection of illuminated manuscripts, early printed books and other art treasures was bequeethed to the library of the FitzWilliam Museum at the University of Cambridge. In 1865 he married Ellen Greg, with whom he had three sons and two daughters.