How a Telescope Works
A telescope is a device that allows us to bring distant objects closer to us so that we can study them. A good example is the many planets, galaxies, and stars in outer space. Some range from $1 at the toy store to the $1.2 billion Hubble Telescope. There are two types of telescopes. Refractors use a glass lens. Reflectors use mirrors instead of a lens.
Let's take the different pieces of a microscope and see how they work. The objective lens in a Refractor or primary mirror in Reflectors gather incoming light and brings it to a focus. The eyepiece takes that same light and magnifies it to take up a large part of the retina of the eye. Thus, it takes a small image and spreads it out to make it look bigger.
There are two general principles to any telescope. One is how well it can collect light. The other is the magnification of the image you are viewing. Collecting light is related directly to the diameter of the lens. The more light collected, the brighter the image. Magnification is the ability to take an object as a far distance and enlarge it so you can see it clearly.
Any magnification can be obtained by using different eyepieces depending on the object you are trying to view. Here is a simplified explanation. Obtain two magnifying glasses and a piece of paper. Hold one of the glasses between you and the paper. At this point, the image will be blurry and unreadable. Take the second glass and place between your eyes and the first glass. Moving the second glass up or down should bring the piece of paper into view. It will be larger and upside down though. Give it a try and see what happens.
Historical Timeline For the Telescope
It seems all the technology for telescopes started back in 2560 BC. Artisans in ancient Egypt polished rocks, glass, and semi-precious stones to make eyes for the sarcophagi. What follows is some major points in the history of how telescopes came to be today.
In 470 BC, Mozi, a Chinese philosopher, focused the sun's rays by using concave mirrors. In 4 BC, Seneca the Younger used water to magnify letters and words. In 23, Pliny the Elder discovered doctors using a crystal ball with the sun's rays beaming through it to cauterize wounds. In the ninth century, telescopes were possibly made from Visby lenses, a Middle Eastern glass. In 1520, Leonard Digges, an English mathematician, invented two telescopes – Reflecting and Refracting.
In 1608, A Dutch lensmaker, Hans Lippershey, applied for a patent on a design for a telescope. In 1609, Galileo improved on Lippershey's design and renamed it "perspicillum" - An Italian word for telescope. In 1616, Niccolo Zucchi invented a reflecting telescope. In 1663, James Gregory, a Scottish mathematician, produces a telescope with a parabolic primary mirror and an elliptical secondary mirror. In 1668, Isaac Newton designed a telescope using a parabolic primary mirror and a flat diagonal secondary mirror. In 1733, Chester Moore Hall created the achromatic lens. In 1880, Ernst Abbe invented the first orthoscopic eyepiece.
In 1910, The Ritchey-Chretien telescope that is used in many of the large astronomical telescopes is invented by George Ritchey and Henri Chretien. In 1930, The Schmidt camera is created by Bernhard Schmidt. In 1937, Grote Reber developed a telescope for wavelengths ranging from radio to Xrays. In 1944, The Maksutov telescope is designed by Dmitri Maksutov.
In 1962, The UK launched an orbiting solar telescope. In 1990, the Hubble Telescope was launched into space. In 2013, the James Webb Space Telescope will be launched and take the place of the Hubble. And this all started with the polishing of a few stones.
Finding The Telescope That Meets Your Needs
There are so many choices of telescopes out there. What do you buy and what do you really need? Here are a few things to keep in mind so you don't buy a telescope that won't meet what you need or want it to do. High power magnification is not always the primary consideration.
You should have 40-60x magnification per 1 inch of aperture. The scope's ability to enlarge an image is dependent upon the lenses used and the focal length within the telescope itself. Most objects can be seen at the lowest magnification because there is more light being focused.
The most important feature to think about when buying a telescope is aperture. Buy as much as you can afford. Remember, though, the biggest telescope is not always the best one. The aperture sizes that follow are usually sufficient: Refractors – 3 inches or 80 mm, Reflectors – 4 to 8 inches or 10 to 20mm, and Compound Telescopes – 6 to 8 inches or 16 to 20 cm.
A focuser can move the eyepiece up and down helping to adjust the focus for each observer. There are two types of focusers – Friction Focusers and Rack and Pinion Focusers. Your telescope sould never shake once while you are using these. In some telescopes, you manot get a choice. Check out the eyepieces that come with your telescope. Some don't come with any.
Make sure you have a couple so you can vary the magnification of the object you are viewing. You also need to be sure that the eyepiece will fit the eyepiece holder in your telescope as not all fit all telescopes. The type of mount you use is extremely important. Ensure it has a low center of gravity so it doesn't tip over. It should not vibrate the telescope and it should be held in place at a comfortable height for you.