Telescopes big and small
Home Telescopes
Galileo's first telescope was actually less powerful and of less quality than the "toy" telescopes or even cheap binoculars of today. And with that, he was able to discover the 4 largest moons of Jupiter. Of course, today we have the bright lights of the big cities that wash most of our sky with their glow. But most of the telescopes we can buy today will still reward you with your own discoveries.
Telescopes today range from the "toys" you can find every Christmas season in the department stores, all the way to the professional "research" grade scopes you can buy from top grade manufacturers. Of course the price range is just as vast, from less than $50.00, to well beyond $50,000.00. The scopes that most of the amatures use range from $400.00 to about $4,000.00. This is more of a reachable price for most of us.
There are 3 main categories that determine the cost of the scopes. The first is the aperture, or size of the optics. Usually measured in millimeters (mm), it can also be listed in inches as they go up in size. The larger the aperture, the more light it gathers and thus, the more you can see in the night sky. Second is the quality of the optics. This varies from manufacturer to manufacturer. This alone can make the cost vary several hundred dollars for the same size scopes. The third category is the mount type and quality. A "dobsonian" mount scope will be cheaper than an equatorial mount. And equatorial mounts can vary in quality so much that the prices of the mounts can easily exceed the cost of the scope that it holds.
The Keck Telescope in Hawaii
Moving on, we look into the telescopes in major observatories. These scopes come in all sizes and types. One of the more popular scopes are the Keck Telescopes in Hawaii. The largest optical telescope in the world, the Keck telescopes are actually two, 10 meter scopes and possibly several more smaller 2 meter scopes that, when completed, will link together through a computer to "electronically" create a telescope larger than several hundred feet! Currently, only the two main scopes are in operation, and the link in still in the testing stages. The 10-meter mirror itself is a first for large telescopes. Rather than a single mirror of 10 meters, it is actually comprised of 36 smaller "hexagonal" mirrors mounted on pistons that can "bend and flex" the mirrors slightly many times a second as needed to compensate for the distortion of the Earths atmosphere.
The Subaru Telescope
Another large telescope we have is the Subaru Telescope owned and operated by Japan. The Subaru is the largest single-mirror telescope in the world with a mirror size of 8.2 meters. The Subaru is also in Hawaii, sitting along side the Keck, and operates in both visual and infrared light.
The Hale on Mt. Palomar
Getting smaller with the big scopes, we come to the Hale telescope on Mt. Palomar California. This is a 5 meter telescope.
The Hiltner on Kitt Peak
Sitting on Kitt Peak in Arizona is another famous telescope called the Hiltner. This is a 2.4-meter telescope.
Sloan Digital Sky Survey
A telescope with an odd purpose would be the SDSS, or Sloan Digital Sky Survey, on Apache Point in New Mexico. This 2.5 meter telescope is designed specifically to take "wide-field" exposures to map the known sky. Only the SDSS is not taking pictures of stars, but rather galaxies. SDSS is slowly creating a map of galaxy clusters, and where we sit in the whole scheme of things.
The Hubble Space Telescope
The most well known telescope is the Hubble Space Telescope orbiting the earth. The reason for doing this was to get the scope beyond the distorting effects of the earth's atmosphere. Doing so allowed scientists to take photos of extremely long exposures with perfect quality. Of course, when the Hubble was first used, a major flaw was discovered that revealed distorted and out of focus images. Many people remember the news about Hubble's "poor-eyesight". The 2.4-meter mirror that was ground to exacting specifications was not compensated for one thing. Gravity! Once the telescope was in space, the telescope did not have the earth's gravity to "flex" the mirror. And, since the mirror was made without compensating for this, it was useless in space. A space shuttle mission to fix the scope was made, and Hubble's vision was restored. We were seeing much more than we ever expected. An example of this can be found in the "Hubble Deep Field North" image. This image is of an area of the sky, in the scoop of the Big Dipper, that when viewed from Earth reveals nothing, but in Hubble's image thousands of galaxies are shown.
The Chandra Observatory
Another space-bound telescope in use today is the Chandra Observatory. This telescope operates in the X-Ray bandwidth rather than optical. This telescope picks up the x-ray radiation put out by many stellar objects. We can combine these images with the optical images to give us a better "picture" of what's really out there.
COBE
This space-bound telescopt measures the diffuse infrared and microwave radiation from the early universe. Using the COBE satilite telescope, we now have pictures of what the Universe possibly looked like when it was very young, and still very hot.
SOHO
Yet another space-bound telescope is stationed between the earth and the sun, and whose sole purpose is to study the Sun. The Solar and heliospheric Observatory, or SOHO, views the Sun in several wavelengths, including optical, and can even create its own "eclipse" of the Sun so scientists can study the Sun's corona, and solar flares.
The Future
Future telescopes in space are also in the works. One plan is to put up several telescopes, all linked together to create a very large array telescope similar to the Keck, called an "Inferometer". Scientists hope to use such a telescope to finally see planets around other stars directly.