In 1862 he became a partner in the firm of Messrs. McClean and Stileman, eventually retiring in 1870 to work on astronomy and live at Tunbridge Wells, at Ferncliffe with his wife, Ellen (née Greg) and children (three sons and two daughters).
[2] He did important spectrographic work in astronomy, inventing his well-known star-spectroscope in 1875 and observing solar prominences.
After two years' work he finished the northern sky (publishing the spectra of 160 stars in the journal Nature).
[3] His spectrographic survey of the stars was cited in the presentation to him of the Gold Medal of the Royal Astronomical Society in 1899.
Frank McClean died in Brussels, Belgium, and is buried in Kensal Green Cemetery, London.