History Of The Spyglass
The spyglass was an important instrument for nautical use when the telescope was first invented. In 1608, three people are known for claiming credit to developing the first telescopes. However, it was Jacob Metius from the Netherlands who had produced a ‘spyglass’. Metius’s spyglass used an objective lens measuring 15 mm in diameter on one end and used a double concave eyepiece lens at the other. This gave his spyglass a magnification of about 3x. Thomas Harriott used one of these spyglass inventions of Metius to stare at the moon, and made remarkable drawings at the time that depicted many of the moon’s features.
Not long after Metius’s invention was used to peruse the land markings of our very own moon did Galileo begin to take interest in the telescope concept. He devised his own improved telescope that measure thirty-eight inches in length. After which he consistently improved upon the design using larger objective lenses, longer tubes, and stands to keep the telescope stable.
Johannes Kepler was the next to improve upon the spyglass originated by Metius, and improved upon by Galileo. Kepler decided it would be wise to thin out the objective lens, and make the eyepiece convex. He figured that these renovations would give the telescope a larger area of vision without suffering from the “fuzziness” that plauged Galileo’s own take on the spyglass. While Kepler himself never did get to build his design, it would be created by many others.
Even though Kepler sought to improve upon Galileo’s design, his own suffered from a crippling flaw. This was because his idea to input a thinner objective lens into his design made it so incoming light was bent less. This meant that the eyepiece would have to be further away than it was – an fl of about 100 feet to be exact. This length was very impractical and therefore they were not of much use.
While Metius’s spyglass and Galileo’s and Kepler’s contributions to its advancement were enormous leaps and bounds in technology, all of these early telescopes were pluaged with problems. The problem being a harsh “chromatic aberration”. What this meant was that white light being comprised of different colors at differing frequencies became bent by the lenses at different angles creating a “rainbow of colors around the image”. The result of which made Galileo’s telescopes’ suffer from such harsh fuzziness.
It wasn’t until the 1700s that it was discovered that different types of glass (as well as different shapes) had varying effects on bending light. Chester Hall, created a concave lens out of flint glass, and a convex lens from crown glass that when combined made no chromatic aberration. John Dollard improved even more so on this by actually cementing the lenses together, abolishing the nasty spherical aberration. However, the problem of creating a larger objective lens that did not suffer from bubbles was still at hand.
Despite the many flaws of early brass spyglasses and telescopes, they were still very essential to the way the world would shift in the 17th and 18th centuries. The improvements in technology made these devices capable of exploring more deeply into outer space as well as our own world.