The telescope is a painstakingly crafted and finely ground porthole to the universe. Though the scope is a remarkable feat of workmanship, its own reflections, scratches, and smudges rarely attract an observer's eyes. Beyond the glass is the real attraction, a planet, moon, star cluster, or distant galaxy. Yet naked, nature's attractiveness is overlaid by chaos. The principles of science, coupled with telescopes, penetrate the chaos of nature; from this new vantage point, beauty is unveiled.

Astronomical observatories have revealed bright roses in the ubiquity of space. To a naked eye, the night sky is simply a revolving pattern of bright specks, but a few mirrors and lenses can probe far deeper than these points of light. In fact, some objects are so far that light, travelling 300,000 kilometers per second, still takes billions of years to reach the earth. When the light was sent by these distant stars, galaxies and quasars, the universe was still in its childhood.. Therefore, nature itself is an enormous time machine laying out a timeline for telescopes to scan from beginning to end.

These instruments only came into use a few centuries ago when Galileo discovered their value. Though the Dutch had developed several telescopes, Galileo was the first to use one on the heavens. He quickly increased his original 4 X magnification to 30X and proceeded to bring the study of astronomy to a whole new level (Giancoli, 719).

Today, there are three basic types of telescopes, all with the same purpose: to gather light from the universe and to magnify it. Light from the moon or farther is essentially parallel (Kuhn, 491). This is because the angle between the two ends of any telescope is immeasurable. The sine of an angle is proportional to the opposite side, half of a ~ 1 meter telescope, divided by the adjacent side, distance to the moon = 384,000,000 meters (Giancoli, i). This ratio equals ~ 1.3 x 10-9, which taking the arcsine, is 7.5 x 10-8 degrees. Rays with an angle this small are essentially parallel and no telescope could have the precision optics to correct for the 7.5 x 10-8 degree difference from parallel lines.

Most stellar objects are far too faint to be seen with the naked eye. This is because light decreases with the square of the distance. Stars brighter than the sun become nearly imperceptible faint points of light when they are many light years away. One way to collect the light is a parabolic mirror. For an informal proof of why a parabolic curve reflects parallel light to a point, see the attached sheets. The other option is a large lens in a telescope known as a refractor.

Refractors, sometimes called Keplerians, take advantage of Snells law, which basically states that light will bend in different mediums (Giancoli, 719). If a glass lens (a different medium than air) is shaped right, parallel light will bend all to one point, just like a reflecting parabola. While these two light gathering techniques may both work, the refractor has several drawbacks that a reflector does not.

One such obstacle is due to the wave nature of light. Visible light may vary in wavelength from 400 nanometers (violet) to 700 nanometers (red). When visible light travels from one medium to another, the amount of bending is related to the wavelength. Therefore, the focal length of red light is different from the focal point of violet light. This effect is called chromatic aberration and causes stellar objects to be out of focus. One solution is a diverging lens, called an achromat, which helps bring the difference in focal points down. To further curb the effect of chromatic aberration, an apochromatic refractor may have up to three or four lenses. Unfortunately, these additional correcting lenses can come at a serious price. A typical 100 mm apochromatic refractor costs $3,000-4,000 (Dickinson, 68).

Reflectors, on the other hand, do not have the problem of chromatic aberration because a mirror will reflect light the same, regardless of wavelength. The simplest of these is the Newtonian reflector. This is the cheapest and easiest telescope to make because it only involves shaping one surface, the objective mirror. This can be ground between two circular glass blanks and due to the law of averages, one will be convex and the other concave. The concave blank can be coated with a mere 100 nanometers of aluminum to make it a reflective spherical mirror. For small telescopes less than eight inches in diameter, no correction must be made to change them from spherical to parabolic because they are so closely the same shape (Texereau, 17).

The rest of the Newtonian is easy to construct. All that is required is a tube with a flat mirror that will bounce the focused light into a hole for an eyepiece. This second mirror must be place directly in the center of the tube, blocking some light that strikes the objective. However this light blockage is not a very large percentage of the total mirror. For a secondary mirror of one inch in radius, the area is equal to (radius)2 = . For an objective mirror of three inches in radius, the area is 9. Therefore, only 1/9 or 11% of the light is obstructed.

Of all the possible mounts, the Dobsonian is the easiest to construct. While store-bought mounts have hard-to-make metal controls, knobs, and slow-motion controls, a Dobsonian can be made of wood and a little Teflon. The mount rotates in two directions and relies on friction to hold it in place. The only problem is that it is not equatorial-aligned (aligned with the axis of the earth), so an observer must constantly adjust the view to keep an object in place. Despite this fact, the Dobsonian is far easier to set up; it can simply be placed on the ground and the Newtonian is ready to go (Dickenson, 68).

The two drawbacks to a Newtonian are that they have a slow cool-down time and that they must be collimated. The cool-down time can be alleviated by letting the mirror be relatively open to the air, so it may reach air temperature quickly. Otherwise, there are air currents inside the tube that cause distortions to the image. The latter problem with Newtonians occurs because the mirror falls out of alignment. Every time it is used it must be collimated (or realigned) to be straight. Fortunately, by shining a laser through the eyepiece, this realignment can be accomplished easily and quickly (Roth, Jan. 22).

The final telescope type is the compound telescope called a catadioptric. These combine a lens and mirror to form a powerful, yet manageable instrument. The most typical example of these is the Schmidt Cassegrain. This uses a weak lens and two mirrors. The light enters through the lens, bounces of the objective mirror, and finally off the secondary mirror for a total of three tube-length-traverses. This enables it do pack a long focal length into a small and transportable space. Focal length plays a large role in magnification because the formula is magnification = (telescope focal length / eyepiece length). An increase in focal length with the same eyepiece, therefore, will increase magnification. Additionally, the front lens protects the inside of the tube from collecting dust (Roth, Jan. 22).

The professional telescopes in the world work on the same principles as the aforementioned ones. The majority of them are larger for two reasons. The first is that an increased diameter will collect more light because it reflects or refracts more photons than a smaller diameter. The second is that, due to the wave nature of light and interference, there is a theoretical limit to the magnification of a telescope, but a larger diameter mirror will have a higher theoretical limit.

As the telescope size grows, weight becomes a problem. The glass in a huge refractor is so heavy, it flexes under its own weight and no longer refracts light properly. To support a 50 inch lens, reinforcements would be needed on the glass, however, reinforcements would block light, so an enormous refractor is not feasible. The largest refractor in the world, created by George Ellery Hale in 1897, has a 40 inch diameter. It pushed the design-limit of a refractor and no larger one has been built since. Reflectors, however, may be supported from underneath, so their weight is a manageable problem.

Hale raised funds for the building of three more telescopes, each a reflector. The final one, named the Hale telescope, was completed in 1938, after his death. This 200 inch reflector still functions well for research on top of Palomar Mountain, California (Fraknoi, 115). See the cover page for a picture.

Since these times, professional observatories have expanded in every dimension. The obvious dimension is in size. While they continue to increase in diameter, a newer trend is to combine the light of several smaller mirrors. For example, the Very Large Telescope, VLA, in Chile is the largest observatory in the world, but it does not have the largest mirror. It has four eight meter smaller mirrors that combine to form, effectively a 16 meter mirror. The largest single telescopes are the Keck I and Keck II in Hawaii, both ten meters in diameter (Kuhn, 489). These monstrous telescopes have reached the limit of what is possible in the atmosphere. Due to air currents in the atmosphere, there is a limit to the amount of detail one can see. Yet, there are ways of alleviating the atmosphere's effects. Locating an observatory on top of a mountain in dry air drastically improves the seeing. Also being developed is adaptive optics, in which the mirror flexes slightly to accommodate for imperfections in the atmosphere.

Another expansion of modern telescopes is in location, the best being space. The world famous Hubble Space Telescope is well above the thick and unstable atmosphere surrounding earth. This allows it to have far greater resolution (definition) than instruments many times its 2.4 meter mirror. Though it was launched in 1990, it unfortunately had a flaw in the mirror shape that took three years to fix. From then on, the Hubble has taken thousands of breathtaking and groundbreaking images of the universe. (Fraknoi, 124). Only recently has it started to break down. It remains to be seen whether or not NASA will repair the Hubble.

A final dimension of expansion occurred in the reception of light. Though humans only see in the range 400 nanometers to 700 nanometers, light's wavelength can be longer then a kilometer and shorter than a picometer (10-12 meters). The longest of these wavelengths in the radio wave. This source of radiation can conduct current in a wire known as an antenna. This electric current may be amplified and then recorded as a signal. Finally, the data stored can be represented by visible colors in a chart to give a visual image of the radio "picture" (Fraknoi, 119).

This information provides astrophysicists with valuable information about the universe's history. Light from farther away, and therefore farther back in time, tends stretch out because velocity increases with distance in the universe. This phenomena is called "redshifting." Only telescopes that capture radio waves and microwaves, which are slightly shorter in wavelength than radio, may receive this ancient, stretched-out, light.

Radio waves are much harder to focus than shorter wavelengths because of the wave nature of light. Longer wavelengths interfere and cancel each other out to a greater degree than visible light, so even larger "mirrors" are required. Fortunately, making large radio telescopes is far easier because a simple wire mesh will reflect the radiation. For example, the Arecibo observatory in Puerto Rico has a 305 meter diameter reflecting surface, a size not nearly achievable for a visible light mirror with today's technology (Fraknoi, 122). Another technology, called interferometry, also can increases the resolution of a radio telescope. This involves the accurate timing of the antenna signals. The difference in time of reception can provide a greater approximation of location and therefore, provide greater resolution. The best of these, the Very Large Array in New Mexico, can achieve a resolution of .0001 arcseconds, while the Hubble only achieves .1 arcseconds (Fraknoi, 121).

Other wavelengths include infrared, ultraviolet, x-ray, and gamma rays. Combining all these together provides a useful map of the universe and its history. The most difficult of these forms of radiation to measure is infrared. This is because everything is constantly leaking infrared radiation: the earth, the air, and the telescope itself. For this reason this is the least explored wavelength of all (Fraknoi, 113).

A future observatory may fill this gap in scientists' knowledge. Formerly called the Next Generation Telescope, the James Webb Telescope (JWT) will ride along earth in space to explore infrared light. Unlike the Hubble, it will not be fixable or serviceable, but will cost only one third the price. This will enable it to see galaxies and stars anywhere from several million to a few billion years old. In order to avoid the infrared radiation from earth, it will travel and the second Lagrange Point. This is an orbit around the sun that trails the earth. From this location, the JWT will help reveal how dark matter, galaxy evolution, and planetary formation all work (James Webb, 22 January).

Another future generation of scientific instruments are liquid mirror telescopes (LMTs). Rather than having a solid reflecting mirror, these have a spinning liquid mercury mirror. This modification can significantly reduce the building costs, but does have limitations. The mirror must always face straight up, meaning that only a small portion of the sky is observable.

The Large Zenith Telescope is the most operational of all LMTs, though it is still being developed ten years after its creation. Its six meter diameter liquid mirror is spun around so that centrifugal force will push it into a parabolic shape. This is an engineering difficulty because the mirror itself ways three tons. The solution is an air pressure bearing that can both support the enormous weight and spin freely (The Large Zenith, 22, Jan).

Future plans are being made for a much larger observatory. The Large-Aperature Mirror Array (LAMA) will consists of eighteen separate ten meter diameter LMTs. Combined together, they will produce the equivalent of a 42 meter diameter reflector, making it the largest visible light scope in the world. It is still in its design phase and has no definite location yet (Large-Aperature, 22, January).

The fundamental goal of a telescope is to search for beauty. Whether it be a small amateur "sightseeing" refractor, or a multi-million-dollar enterprise, the goal is the same. While aesthetic beauty is observed with the former, the latter brings out scientific beauty, revealing through numbers and equations the universe's inner workings. Be it a picturesque view of the Andromeda Galaxy or the confirmation of the Moser Twist Theorem, the universe's magnificence is realized with the simple bouncing and bending of light.

Dickenson, Terence. Night Watch. Buffalo: Firefly Books, 1998.

Giancoli, Douglas C. Physics: Fourth Edition. Englewood Cliffs: Prentice Hall, 1995.

"James Webb Telescope Home Page." 22 January, 2005. <http://www.jwst.nasa.gov/home/>

Kuhn, Karl F. Astronomy. A Journey Into Science. St. Paul: West Publishing Company, 1989.

"Large-Aperture Mirror Array." 2001. 22, Jan. 2005. <http://www.astro.ubc.ca/LMT/lama/index.html>

Roth, Joshua. "Choosing Your First Telescope." 22 January, 2005. <http://skyandtelescope.com/howto/scopes/article_241_1.asp>

Texereau, Jean. How To Make a Telescope. New York: Interscience Publishers, Inc., 1951