Around 1551, he invented the theodolite as well as inventing and improving a number of other items for use by surveyors, carpenters and masons. More importantly, around the same time, he apparently invented the telescope, both refracting and reflecting. Here's what his son, the famous English astronomer, Thomas Digges, wrote in the preface of one of Leonard's books:
"He may wonderfully helpe him selfe, by Perspective glasses. In which (I trust) our posterity will prove more skillfull and expert, and to greater purposes, than in these days, can (almost) be credited to be possible."and about the reflecting telescope:
"..... my father by his continual pain-full practices [practical experiments], assisted with Demonstrations Mathematicall, was able and sundrie Times hath by proportionall Glasses duly situate in convenient angles, not onely discovered things farre off, read letters, numbered peeces of money with the very coyne and superscription thereof, cast by some of his freends of purpose uppon Downes in open fields, but also at seven miles declared what had been doon at that instant in private places....."There are stories that Digges met Giordano Bruno during his visit to England.
The first of his Leonard Digges's books, "The General Prognostication," was published in 1553. It was expanded and republished in 1555 as "A Prognostication of Right Good Effect" then revised again the following year with the title "Prognostication Everlasting." These books became best sellers and enhanced Digges's reputation partly because they were written in English when standard scientific publications were normally in Latin. The Prognostication books were actually early almanacs with data for astronomy and astrology, calendars of church events and moon motions for several years, information on timekeeping and weather phenomena and even instructions for bloodletting. It also described the universe as it was understood at the time by the Ptolemaic system (even though Copernicus's book " De revolutionibus orbium coelestium" had been published ten years before). His next book, "Tectonicon" dealt mostly with surveying and came after some troubles Digges ran into.
Perhaps one reason nothing ever came from his telescope inventions was that Leonard's career hit a brick wall when he took part in an unsuccessful rebellion in 1554 led by the Protestant Sir Thomas Wyatt against England's new Catholic Queen Mary who took over the throne in 1553 from her father Henry VIII. Originally Digges was condemned to death, but had his sentence commuted, instead forfeiting all his estates. He spent the rest of his life trying to regain his properties and reputation.
Leonard Digges died in 1559 when his son Thomas was 13 years old. Thomas later published one of his father's manuscripts, "Pantometria," posthumously. It is from the preface to this book that we quote above.
