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The Stars
Telescope Jargon
There is a language of astronomy. You need to know what the terms mean before you buy a telescope to ensure that you buy the telescope that is best suited for your needs. Some of the terms you will hear are:
1. Magnification and aperture: On the box that a telescope comes in, these two terms are represented by numbers like 6 x 30 or 8 x
50.
a. The first number represents the magnification. The number 6 means that distant objects appear to be 6 times their size when viewed through the telescope. Magnification is not as important, however, as aperture.
b. Aperture is represented by the second number and tells you the surface area of the lens or mirror of the telescope. The primary function of a telescope is to gather light. Aperture is more important than magnification in viewing celestial objects.
2. Focal length: Focal length is the distance that light travels from the telescope's lens or mirror to the focal point inside the telescope. The size of the image at the focal point will be larger the longer the focal point is.
3. Focal ratio: The term "focal ratio" is the ratio between the aperture and the focal length.
4. Refractor telescope: The refractor telescope gathers light through the use of a lens. Refraction is one of three ways in which telescopes gather light.
5. Reflector telescope: A reflector telescope gathers light through the use of a mirror.
6. Catadioptic telescope: A catadioptic telescope gathers light through the use of both lenses and mirrors.
7. Equatorial mount: An equatorial mount is a telescope mount with one axis that is parallel to the earth's axis, and points to the celestial North Pole.
8. Altazimuth Mount: An altazimuth mount is a telescope mount with two axes. It allows for movement in two directions, horizontally and vertically.
See Also:
Star, Stars, Constellations at SPACE.com
Deep Sky Objects
The Planet Venus
Back in 1686, a French scholar by the name of Bernard de Fontenelle, wrote, "I can tell from here...what the inhabitants of Venus are like; they resemble the Moors of Granada; a small black people, burned by the sun, full of wit and fire, always in love, writing verse, fond of music, arranging festivals, dances, and tournaments every day."
Nice try, Bernard, but you had it all wrong. Back in those days, it was generally accepted that Venus was much like Earth. Venus is about the size of Earth, but that's pretty much where all resemblance ends.
Almost all of the planets in our solar system travel around the sun in a counterclockwise direction…all of them except Venus and Uranus, that is. Venus (as well as Uranus) travels clockwise. All of the planets except Venus and Uranus rotate on their axis in a counterclockwise direction. Venus and Uranus rotate clockwise.
Venus also rotates really slowly, too. A "day" on Venus would equal about 243 Earth days. Venus is covered by a thick layer of clouds that make studying the surface very difficult. In the last 30 years, however, astronomers have learned how to "see" through the thick cloud cover.
In 1962, Mariner 2 was the first spacecraft to go by Venus. Since then, there have been 20 more missions. The first hard landing on Venus was done by Venera 4 in 1967. The first soft landing was done by Venera 7 in 1970.
In 1989, the Magellan spacecraft probe was launched. Magellan rotated around Venus from 1990 to 1995. It then burned up in the atmosphere of Venus. Magellan bounced radar signals off the surface of Venus and transmitted the data back to Earth. |
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More articles:
History of astronomy - Wikipedia, the free encyclopedia
Buying a Telescope. Advice and guide for Buying Telescopes
Planting by the Moon Phases - by E. A. Crawford
Buying a Telescope
The Sun
The Planet Mars
Nicolaus Copernicus
Nicolaus Copernicus first became fascinated with astronomy in 1492 when he enrolled in Kraków Academy (now Jagiellonian University). His professor, Albert Brudzewski, is credited with introducing young Nicolaus to astronomy.
After four years at Kraków Academy, Nicolaus Copernicus's uncle (who paid for his education in hopes that Nicolaus would become a bishop) sent him to Bologna to study civil law. It was there that Nicolaus met Domenico Maria Novara da Ferrara, who was a famous astronomer of the time.
Copernicus gave some friends his Commentariolus (Little Commentary) in 1514. Commentariolus was a short handwritten work that described
his ideas about the heliocentric (sun-centered universe) hypothesis. It was the basis for his later work.
Copernicus feared ridicule from other scientists. He wasn't afraid of what the Church would think of his theories. This fear of ridicule caused him to delay publication of his findings for several years. As a matter of fact, his book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) wasn't published until the year of his death in 1543.
It is said that Copernicus was in a coma that had been caused by a stroke when a friend put a copy of his book into his hands. Copernicus awakened from his coma and died peacefully shortly there after.
There are six major parts to the Copernican theory:
1. Motions of the planets are uniform.
2. The sun is the center of the universe.
3. The order of planets around the sun is Mercury, Venus, Earth and Moon, Mars, Jupiter, Saturn, and the fixed stars.
4. Retrograde motion of the planets can be explained by the Earth's motion.
5. Daily rotation, annual revolution, and annual tilting of its axis are the three motions of the earth.
6. Comparatively speaking, the distance between the earth and the sun is small to that of the earth to the stars.
Related Topics: Carl Sagan,
Astronomy Clubs, The Stars
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