Much of his work was expanded on, annotated, and published by his son, Thomas Digges. His son followed in his footsteps and was a pivotal player in the popularisation of Copernicus's book "De revolutionibus orbium coelestium". Notes written by Thomas Digges in the publication of the book "Pantometria" in 1570 contain descriptions of how Leonard Digges made use of a ""proportional Glass"" to view distant objects and people. Some, such as astronomer and historian Colin Ronan, claim this describes a reflecting or refracting telescope built between 1540 and 1559, but its vague description and claimed performance makes it dubious.