Celestron is the world’s leading manufacturer of telescopes for amateur astronomers. And in 2020, the company, based in Torrance, California, is celebrating its 60th anniversary as a maker of astronomical equipment.
Most readers of Astronomy who observe the sky have either owned or viewed through Celestron equipment. So, we thought it fitting to take a look at the history of this important company and perhaps glimpse what the future may hold.
The 1950s and ’60s
American electronic engineer Tom Johnson founded the parent company of Celestron, Valor Electronics, in 1955 in Gardena, California. The company produced components for both industry and the military.
A few years later, Johnson was searching for a telescope for his two young sons. When he didn’t find one that he thought was good enough, he built a 6-inch reflector. The project got him interested in constructing telescopes, so he began building larger and more complex instruments. Believing that his hobby could grow into a full-time business, he created an astro-optical division within Valor Electronics in 1960.
On July 28, 1962, Johnson brought a portable 18¾-inch Cassegrain reflector to a star party hosted by the Los Angeles Astronomical Society on the summit of Mount Pinos, in the Los Padres National Forest. He had built the scope from surplus parts in six months, and for only $1,000. Attendees loved his telescope and many asked him if he would build more.
Rather than duplicate his telescope, Johnson created a Schmidt-Cassegrain (SCT) design, which incorporates features of a refractor and a reflector. He then invented a method to produce it in quantity.
Johnson’s biggest challenge was making the glass corrector plate, the SCT’s front optic. This thin piece of glass contains a subtle curve, allowing it to “correct” the errors introduced by the spherical mirror the scope uses, and, at first, it was difficult for Johnson to create them in quantity.
Once that hurdle had been overcome, his 20-inch SCT, the Celestronic 20 (C20), was ready for sale. In May 1964, the new company he created, Celestron Pacific (a division of Valor Electronics), advertised C20s for sale.
In December of the same year, Johnson changed Valor Electronics’ name to Celestron Pacific. Later, he dropped “Pacific,” and Celestron was born. By 1969, the company was advertising a full line of SCTs: the C6, C8, C10, C12, C16, and C22.