He specialized in making micrometric measurements of double stars. He made a special study of telescopic resolving power, and in 1867 he drew up a table showing what aperture of telescope is necessary to resolve two stars of a given separation (the Dawes limit). In 1850 he observed Saturn’s ‘crêpe ring’ (the C Ring) independently of W. C. Bond and G. P. Bond, but 10 days after they discovered it.