For many years, chromatic abberation was a sufficiently serious problem for lenses that scientists tried to find ways of reducing the number of lenses in scientific instruments, or even eliminating them all together. For instance, Isaac Newton developed a type of telescope, now called the Newtonian telescope, which uses a mirror instead of a lens to collect light. However, in 1758, John Dollond, an English optician, discovered a way to eliminate chromatic abberation. He combined two lenses, one converging, the other diverging, to make an achromatic doublet. The two lenses in an achromatic doublet are made of different type of glass with indices of refraction chosen such that the combination brings any two chosen colours to the same sharp focus.
Modern scientific instruments use compound lenses (i.e., combinations of simple lenses) to simultaneously eliminate both chromatic and spherical aberration.