Clyde William Tombaugh was born on February 4, 1906. He spent most of his childhood on a farm near Streator, Illinois. In 1922, the family relocated to a farm in western Kansas. Tombaugh glimpsed his first telescopic view of the heavens through his uncle Leon's 3-in (7.6-cm) refractor, a kind of telescope that uses a lens to gather faint light from stars and planets. In 1925, inspired by an article in Popular Astronomy, Tombaugh bought materials to grind an 8-in (20.3-cm) light-collecting mirror for a reflecting telescope. He ground that first mirror by hand, using a fence post on the farm as a grinding stand.

The finished instrument, a 7-ft-long (2.1-m), rectangular wooden box, was equipped with wooden setting circles for aligning it to objects of interest in the sky. Tombaugh had not ground the mirror very accurately, and thus the telescope was unsuitable for the planetary observing he had in mind...