TELESCOPES

Man has always followed the heavens. Ancient creational Myths and Legends always connected with Gods and Goddesses linked to celestial bodies.

It was only a matter of time before humanity could find a better way to peer into the heavens for a closer look at their Gods and Goddesses.

To truly understand what the sky and its lights are all about, human beings eventually realized they couldn't just rely on their eyes. They had to develop tools to help explore what stretched far above them. The telescope was the key invention in the progress to modern astronomy, but it took many thousands of years before anyone succeeded in inventing one. This is somewhat surprising since water's ability to change and sometimes magnify objects beneath the surface must have been noticed as early as caveman times.

Glass was discovered around 3500 BCE, and crude lenses were even found in Crete and Asia Minor, dating from 2000 BCE. A number of well-respected writers as early as classic times reported about refraction, reflection, and magnification. But for some reason no one put together all these observations and discoveries in the right way until the early 17th century. Instead, ancient peoples used many other kinds of tools and aids to help them observe and track the stars and planets.

Ancient sites like Stonehenge in Great Britain and the Egyptian pyramids are some of the earliest evidence we have that our ancestors made pretty accurate observations of the sky. We know that because these sites are aligned in special ways. At Stonehenge, for example, one can see the sun rise through one arch at the summer solstice, which is the time when the sun is at its farthest point north in the sky.

The sun rises and slips just above a distant stone called the Heel Stone. Some sort of measuring tools were likely used to arrange the site in such an exact manner, to produce this effect. We may never discover just why this early society aligned their stones this way. It could be to create a "sacred space" for religious ceremonies or magical practices. It is now believed unlikely that Stonehenge was an early observatory, but there's little doubt that the alignment was made on purpose and that the sun was meant to appear where it does at that time.

The pyramids in Egypt are also aligned in a specific way, but in their case it was to point at certain stars. Two shafts which lead down into opposite sides of the Great Pyramid at Giza open on one side to the star Thuban (at the time, the closest star to being the north star) and on the other to the stars in the constellation Orion's belt.

But since the pyramid was built to be a tomb, like Stonehenge it is not considered an observatory. The pyramid was supposedly a launching pad for the dead pharaoh's soul.

The pharaoh was expected to travel to heaven and continue his destiny there, and the shafts pointed in such a way to symbolically guide him to his new, heavenly home. Actually, even a living person standing in the crypt could not see the alignment of stars, since the shafts were blocked. But the ancient Egyptians obviously had some dependable knowledge of the stars' positions in order to arrange the shafts' alignments in the first place.

Many other ancient sites have been found, in Central and South America, the U.S., and Ireland, which suggest they were built to point at certain stars or the sun or moon. We will probably never know for sure why these structures or patterns were made, but their existence does at least prove that men and women have been interested in the sky's changes for a very long time, and that they kept close track of where heavenly objects appeared.

As time went by, people devised portable aids to star watching that have survived for us to examine. Egyptians invented the merkhet, which was used by two observers facing one another.

Each one held a merkhet, and they sat lined up so that one could see the north star just above the other's head. The second person then sat very still as the first one watched and recorded when stars passed by the top of the other's head, by his ear, shoulder, etc. In this way, astronomical positions were recorded so people could predict how the stars moved.

In Alexandria around the 2nd century, Ptolemyand his contemporaries invented more instruments for sky watching . To use a quadrant, one side was aligned with the horizon and the other pointed at the zenith, the spot in the sky directly overhead. Then a movable arm or bar was pointed at a certain star, to measure its distance above the horizon. Quadrants also could point to the sun and tell the time of day. They were used a lot even after the discovery of the telescope, since early telescopes couldn't measure exactly where a star was.

From Alexandria, the center of learning moved to the Middle East, where Arabian astronomers used many fine star-measuring instruments. The astrolabe was either invented or improved at this time; it was used like a quadrant, except one held it by a ring at its top and gravity put it into position to measure the sun or stars.

The cross-staff, just a simple cross with a movable bar, was invented by Jewish astronomer Levi ben Gerson (1288-1344). With a cross-staff, mariners could determine the angle between the moon and a star by sliding the bar so the two objects were aligned with the ends of the bar. Then the angle was read off a scale engraved in the middle.

Many instruments were constructed to be larger and larger, so that very exact measurements could be made. One quadrant built was 180 feet in size! Tycho Brahe (1546-1601), just before the age of the telescope, had huge instruments at his observatory, Uraniborg, built on an island off Denmark. There astronomers and their assistants could use quadrants and Tycho's improvement of the cross-staff, sextants.

Of these first observatories, built to house large instruments, few survive. While some were just abandoned, like Uraniborg, many in the Islamic world were destroyed when the benefactor or ruler who built it died.

Astronomy was at this time tied up with astrology, and so star and planet positions were tracked mainly to forecast the future. But such fortune telling was forbidden by Islamic law. Sky watching was actually a risky pastime in those days. One such sponsor of an observatory was executed and his building and instruments destroyed, all because he was found guilty of, among other things, "communicating with the planet Saturn."

It was this kind of superstitious belief that hampered the progress of astronomy. From the third through the 13th century, the ability of certain kinds of curved glass to magnify objects was variously reported, but such a thing seemed so amazing that it appeared to some to be "black magic." Claims made by a prospective discoverer were either disbelieved or liable to land that person in prison or to be burned at the stake. Not until the Renaissance, when the scientific age began to dawn, were people better prepared for the miracle of the telescope.

Phoenicians cooking on sand discovered glass around 3500 BCE, but it took about 5,000 years more for glass to be shaped into a lens for the first telescope. Even cavemen must have noticed how water refracts, or bends, the image of objects below the surface, but this probably seemed specific to liquid and not to sunlight's angle on the water's surface.

Crude lenses have been found in Crete and Asia Minor that date from around 2000 BCE, but these weren't clear enough to see through. Euclid wrote about reflection and refraction of light in the 3rd century BCE, and the Roman writer Seneca mentioned how Aristophanes demonstrated that a globe full of water could be used to magnify things. So some of the theory that would be the basis of telescopes was known as early as classic Greece times. With these well-known people publishing such results and theories, why did no one think of inventing a telescope?

Perhaps such an instrument was produced, but its use was so amazing that it appeared to be evil, and its maker was hounded or killed. As ridiculous as that sounds, this is what actually happened to Roger Bacon (c1220-c1292). Bacon wrote about magnification and even applied its use to observing the sky. He wrote that by using lenses, "the Sun, Moon, and Stars may be made to descend hither in appearance . . . which persons unacquainted with such things would refuse to believe." For this he was labeled a magician and imprisoned.

It wasn't until the Renaissance, when so many new and seemingly miraculous discoveries were being made, that people were ready for such a marvelous invention as the telescope. What also made it easier to accept was the general use of spectacles by that time. Spectacles or eyeglasses were only invented sometime in the 13th century. Just who invented them is not known, but a curved glass's ability to magnify its surroundings was probably discovered by mistake. Once fashioned so that both eyes could look through two lenses at once, spectacles became instantly popular, a great benefit to those with aging eyesight or those nearsighted from birth.

A spectacle maker probably assembled the first telescope. Hans Lippershey (c1570-c1619) of Holland is often credited with the invention, but he almost certainly was not the first to make one. Lippershey was, however, the first to make the new device widely known. The story usually told is that Lippershey was handling some lenses in his shop when he happened to look through two differently shaped ones at the same time. He was holding them up toward the light of the open doorway, when he was startled to see a distant church tower seem to jump to the door of his shop. He was amazed to see even the weathervane on the church spire clearly. Lippershey's first idea was to use this curious effect to attract customers. He set up a display with the two lenses, so people who came to his shop could look through them and see how the church appeared to be so close. Lippershey eventually enclosed the two lenses in a tube to make what he called a kijkglas or "look glass."

While that story may be partly or wholly fiction, Lippershey did apply for a patent for his telescope and sent one as a gift to the ruling prince of the Netherlands, Mauritz of Nassau. Lippershey was eventually denied a patent, because, he was told, "too many people have knowledge of this invention." This was indeed true, since toy telescopes were already for sale in Paris, and other spectacle makers were also claiming they invented the telescope. Perhaps Lippershey did invent the telescope independently of others - that would not be an unusual occurrence. Whatever the case, it was the news of Lippershey's invention that reached Galileo Galilei in Italy and intrigued him enough to attempt to make his own telescope.

Galileo's version of Lippershey's "far looker," as he heard it called, also wasn't invented specifically for sky watching. Galileo, like Lippershey, saw an opportunity to make money with this new invention. Both these men realized the enormous military advantage of such a tool. As Lippershey gave a telescope to his prince, Galileo fashioned his own tube and presented it to his ruler, the doge Leonardo Dona of Venice. During the early months of showing off his telescope, Galileo exclusively demonstrated how distant objects on land appeared closer.

It was inevitable, though, that one night the moon would catch his attention, and Galileo would think of pointing his telescope at its bright disk. From that moment, Galileo went on to discover new "lands" in the sky above. The craggy features of the moon surprised him, the increased number of stars he saw amazed him, but his most astounding discovery was when he realized four moons were orbiting Jupiter! Galileo published this incredible find, and the news rocked the world, because at that time people believed that everything in the sky orbited the Earth.

Galileo went on to see many more wonders with what was now called a telescope. The telescope gave such a drastically different view of the sky that some people's most cherished beliefs were threatened. Galileo's reports on things like sunspots, for example, got him into trouble with the traditionalists of his time. No one before could really see what was in the sky, not clearly, and so much of what was believed about the universe was based on philosophy and religious ideas .

Galileo started the trend to actually observe and measure objects in the sky, for he showed that the worlds above seemed to obey the same physical laws known to work on Earth. For example, he calculated the height of mountains on the moon after observing their shadows move on the lunar surface. This was a revolutionary idea, to think that an ordinary person could know something about a distant world just by writing down what is seen and then applying basic mathematics to the problem.

Those first telescopes were far from perfect. While distant objects did appear closer, they weren't very clear. It took several hundreds of years and a lot of experimentation to get really sharp images through telescopes. And people were always trying to see farther and farther into space, so the telescope was constantly being improved and sometimes even reinvented.

The kind of telescope first constructed by Lippershey and Galileo was a refracting telescope, which worked by allowing light to pass through two lenses, one convex or curving outward and the other concave or curving inward. As light from the sun, moon, or stars travels through these two lenses to the eye of the observer, it becomes refracted or bent by the lenses.

However, when light is bent through a glass in that way, the different colors that make up light bend at different angles. Just like when light passes through a prism and makes rainbow spots on the wall, or when light passes through a rain shower and makes a rainbow, light through a refracting telescope lens breaks an image into several different colored images.

All these images bunch close together, but they do not align perfectly one on top of the other to produce a unified image. When this happens, the image seems to have a fuzzy appearance. The yellow image is brightest, for example, but its blue and red counterparts are there too, except slightly to one side or the other, just like the separations of a rainbow. So the brightest image looks as if it has a colored haze around it. This "color aberration" or color problem was a real annoyance to the first telescope owners, and this problem, along with a related problem called "spherical aberration," were both due to the curve of the convex lenses and remained unsolved for many decades.

But before the color and spherical problems were even identified, other refinements in telescopes took place. Johannes Kepler (1571-1630) was the first to make significant improvements to the telescope. Instead of a concave and convex lens combination, he proposed two convex lenses, which would increase the astronomer's field of vision. Kepler got this idea by studying the structure of the human eye. With this arrangement, the resulting image in the telescope would be upside-down, but that was a small price to pay for a better view. Another lens could flip the image right-side up, but the final image would not be as bright. Modern refractors still produce an upside-down image, but astronomers who use them to take pictures just publish the photos upside down.

Kepler may not have actually made a telescope like he suggested. He was very nearsighted and probably lacked the practical skill to construct one. Instead he investigated and wrote down theories on optics, the study of light and its changes, and dioptics, the study of how different lenses worked. Kepler was the first to understand the role that light plays in vision. In Kepler's time, people believed that when you saw something, a beam of light came out of your eye and in some way touched the object seen. Kepler insisted that the reverse happens - light bounces off the object and enters the eye, producing an image inside the eye.

Kepler's work influenced many others in the new scientific age. William Gascoigne, an amateur astronomer in England, was using a Kepler-style telescope when part of a spider's web found its way inside the telescope. One small web line happened to fall right at the focus point, so both the thin line and the image Gascoigne was viewing were magnified together. Gascoigne realized that he could more accurately point the telescope using the line as a guide, and he went on to invent the telescopic sight by purposefully placing wires at the focus point. This helped astronomers make more accurate observations and measurements of objects in space, using the thin wires as a reference point.

Sir Isaac Newton (1642-1727) also studied Kepler's work and constructed a telescope along the lines he suggested. Newton also tried to solve the telescope's color problem. He was the first to realize that white light was a combination of all the colors, rather than the absence of all colors, as was generally believed. But Newton eventually decided there was no way to prevent the breaking up of the different colored images once light passed through a refracting lens. He was later proved wrong, but unfortunately Newton's conclusion discouraged others to try. It was 50 years before someone did at last find a way to remove the color blurs in refracting telescopes.

While he couldn't fix refractors, Newton did have a solution to the color problem - he created an entirely new kind of telescope. He just used a mirror instead of a curved lens for the object glass which collects the final image. A mirror wouldn't refract or bend the light, so there would be no color fringes around the image. In fact, a parabolic-shaped mirror was later found to solve the spherical problem, discovered to be a separate problem. Newton's first reflecting telescope was a great advance in clearer viewing.

But reflectors also had problems at the very beginning. Back then, people didn't know how to make mirrors that wouldn't tarnish. Newton's mirror was made of bell-metal, copper, tin, and a little arsenic for whitening. Such a combination got dull quickly and had to be resurfaced, usually a very expensive and time-consuming process. It wasn't until two centuries later that L´┐Żon Foucault (1819-1868) discovered how to layer silver on glass, a process used until layering aluminum on glass was developed.

Newton constructed his reflecting telescope with another smaller mirror facing the main mirror. The smaller mirror angled the image to the side of the telescope, where Newton put the eyepiece, the hole through which to view the image. A Frenchman named N. Cassegrain in 1672 also proposed a reflecting telescope, but instead of a small mirror angling the image to the side, Cassegrain's main mirror had a hole in the center, and the smaller mirror reflected the image back through that hole to an eyepiece behind the main mirror. Newton ridiculed this arrangement; perhaps he was defensive because some thought Cassegrain invented his reflecting telescope before Newton did. Newton was so well respected an authority at the time that Cassegrain didn't challenge this attack and perhaps even felt his idea wasn't a good one. It's interesting to note, however, that one of the greatest telescopes of our time, the Hubble Space Telescope, is designed as Cassegrain suggested.

Refracting telescopes were still used even after reflectors were invented, for a number of reasons. Many more artisans were making lenses than were making the right kind of mirrors for telescopes. Refractors were easier to get, and they revealed a larger area of the sky. People continued trying to improve refractors. In the process, they discovered that magnification increased with the length of the telescope's tube. To get a brighter image, however, the size of the lens called the object glass had to be larger in diameter.

A wider lens could also be made with less curvature, which would reduce the annoying color and spherical problems that still plagued refractors. So the ideal telescope that everyone sought after was one that had the longest possible tube and widest available object glass. The problem with getting such a telescope was that really long telescopes needed scaffolding or long masts and cranes to hold them up. Some shook when a breeze came along, and others collapsed altogether. They were hard to maneuver into position. Some astronomers eventually learned that their problems outweighed their benefits. Advances in firmly securing and maneuvering telescopes had to occur before very large telescopes would be practical.

Despite their awkwardness, longer telescopes with larger lenses helped make more and more discoveries. Saturn's ring was identified by Christiaan Huygens (1629-1695) who, with his brother Constantine, constructed telescopes that were 12, 23, and even 123 feet long. Christiaan Huygens also developed an aerial telescope, an eyepiece joined by a taut thread to the main telescope, that was itself perched on a tall pole.

Many of Saturn's moons were discovered by Jean Dominique Cassini (1625-1712), who used telescopes as long as 17, 34, 100, and 135 feet. It seemed every time Cassini made a longer telescope, he discovered another moon! Cassini also saw that Saturn really had two rings. He mounted one of his long telescopes on a water tower that he had the Paris Observatory move to the observatory grounds at great expense.

Another astronomer, Adrien Auzout, constructed telescopes that were 300 and 600 feet long. He eventually planned to build a telescope as long as 1,000 feet. He hoped it would allow him to see animals on the moon! As time passed, the reports of more moons around planets, moon shadows on Jupiter, and double stars thrilled people, who then wanted the latest improved telescope so they themselves could see such wonders. One rich man, Nicholas De Peirese, had over 40 telescopes. There seemed no end to what a bigger and wider telescope would show.

William Herschel (1738-1822), a musician, became interested in reflecting telescopes after he used one that was just two feet long. He had some refractors but liked the clearer image the reflector gave him. Herschel wanted to see how much better a five- or six-foot reflector would work, but found that no one made the larger mirrors for them. Herschel decided to try and make his own mirrors. He was able to obtain some mirror-making equipment from a man who was giving up the hobby. His first reflector was seven feet long, then he made one 10 feet long. On March 13, 1781, using just the seven-foot telescope, he discovered a new planet, later called Uranus. He thought that what he had found was just a comet, since no one had any clue that there were undiscovered planets. After that success, he built a 20-foot reflector and finally arranged the construction of an enormous 40-foot reflector.

Herschel saw farther into space than anyone had before. He found that many stars were not just simple points of light, but actually quite different from each other when viewed with a powerful telescope. Some were double stars, and others seemed cloudy, which he called "nebula." He was the first to suggest that nebulae might be other galaxies like our own Milky Way. Herschel often examined over 400 stars in a night. This was the first time that stars were examined for themselves, and not just as reference points for observing moons and planets. But his favorite object was Saturn, and he discovered several new moons orbiting the ringed planet.

Herschel continued to make the mirrors for all his telescopes and even made and sold smaller telescopes to help pay his expenses. Herschel polished his mirrors himself, sometimes for 16 hours straight. Often he refused to stop for meals, so his sister Caroline, who herself became a noted astronomer, would feed him as he worked. While his 40-foot telescope was a marvel of its age, the scaffolding he used on his larger telescopes was rickety and dangerous. On more than one occasion he narrowly escaped structures collapsing on him. In the end, Herschel decided that using the 40-foot telescope was often more trouble than it was worth. It took too long to prepare, he had to hire people to help him uncover and maneuver it, and with the limited clear evenings available for observing in England, he found he used his smaller telescopes more often.

Meanwhile, the color problems of refractors was at last solved by putting one flint glass concave lens up against a crown glass convex lens. The different types of glass broke up light at somewhat opposite angles, so all the colors blended together perfectly.

Chester Moor Hall (1703-1771) happened on this combination effect, although it wasn't until John Dollard manufactured many telescopes with this correction that the solution became widely known. Another great improvement was contributed by Pierre Louis Guinand, who developed a way of stirring the glass when it was forming, making it more defect free. This made possible the creation of larger and larger glass lenses, which up to that time always had bubbles or flaws in them when they were made with a very large diameter.

In the 19th and early 20th centuries, advances in mirror making, glass production, and lens grinding led to the construction of increasingly larger and larger telescopes, which in turn led to the building of permanent structures to hold these huge instruments. At first these observatories were built near big cities or where it was convenient for astronomers or their sponsors to visit them. But eventually people realized that where you put your telescope is almost as important as how big you can make it. Locations were chosen where the weather was best for observing, usually a place with a dry and somewhat warm climate. For the biggest observatories, mountain tops became the spot of choice, where the atmosphere was thinnest and least bothered by wind movement, making the view the clearest of all.

At the Dorpat Observatory in Estonia, the Dorpat Equatorial, a 14-foot long telescope with a 9 1/2 inch lens, was for many years the largest refracting telescope in the world. It was called an equatorial because it was mounted in such a way that a clock device could move the telescope at the same rate as the Earth turned. Its movement went opposite the direction of the Earth, so an astronomer could lock onto a star or planet and examine it continuously without having to manually readjust the telescope's position. With the Dorpat, Wilhelm von Struve (1793-1864), the observatory director, did a complete survey of the northern hemisphere. He examined 120,000 stars. Two thousand of them were double stars, of which only 700 were previously known. Struve also directed the Pulkovo Observatory near Leningrad, where a refractor with a 15-inch wide lens was eventually installed.

William Parsons (1800-1867), third Earl of Rosse, constructed at his castle in Ireland what was eventually known as the Leviathan of Parsonstown, a 72-inch mirror attached to a 56-foot tube. He then built a supporting structure around it. The problem of providing a stable foundation was solved by placing the telescope on a platform of 27 cast-iron plates on a base of tree trunks. The whole assembly then rested on a ball and socket set into solid rock. When the telescope was mounted, fortress-like walls, fashioned to match the castle, were raised to shield the telescope on two sides. Lord Rosse employed most of the people in his district to make this grand achievement possible.

In time, many other large telescopes were constructed all over the world, both reflectors and refractors, sporting wider and wider lenses, or mirrors with diameters of astounding size. Large 48-inch reflectors were mounted in Malta and Australia, for example, and in California, the Lick Observatory assembled a 36-inch refractor that helped Edward Barnard discover Amalthea, the first new moon of Jupiter found since Galileo's time. In Wisconsin, the Yerkes Observatory sponsored a 40-inch refractor, although the weather at Lake Geneva was at times so cold that they had to close the observatory dome for fear of damaging the instruments. One astronomer's nose froze to the telescope's metal side as he observed, and he tore off a chunk of skin while pulling away!

George Ellery Hale (1868-1938), who helped raise money for the Yerkes 40-inch refractor, was also responsible for even larger telescopes in California: the 60-inch and 100-inch Mt. Wilson reflectors and the 200-inch Mt. Palomar reflector, called the Hale Telescope in his honor. The 100-inch Hooker telescope at Mount Wilson was the largest in the world for 30 years. Through it, spiral cloud-like nebulae were at last identified as being "island universes" or what we now call galaxies, just like our own Milky Way galaxy.

The 200-inch Hale at Palomar, completed in 1949, then took over as the world's largest telescope. Weighing more than the Statue of Liberty, the huge instrument had the most perfect mirror ever polished. It revealed such wonders as the first quasars, star-like radio sources moving at incredible speeds at the edge of the visible universe.

Astronomer Allan Sandage , the first to spot a quasar and Palomar's most frequent and productive observer, showed the universe to be 10 times larger in size using evidence obtained with the Hale reflector.

The telescope seemed to reveal the farthest parts of the universe. Strangely enough, when it was being built, some people feared it would allow mortals a view of heaven itself! Even in modern times, the awesome power of telescopes could still frighten people as it did in the 13th century.





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