|
Telescope Jargon
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:
Famous Quotes and Quotations
Inspired by Maria Mitchell
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. |
|
More articles:
The Carl Sagan Portal
The Planet Saturn
Mercury (planet) - Wikipedia, the free encyclopedia
Shooting the Moon
Nicolaus Copernicus - Wikipedia, the free encyclopedia
Basic Astronomy Quiz
History of Astronomy
Astronomy is the oldest of all sciences. It has its roots back in the beginning of time. There is evidence of astronomy playing a large role in religious, mythological, and astrological practices of pre-history. Mankind has always looked to the heavens with wonder mixed with a healthy dose of curiosity.
In the earliest cultures, heavenly bodies were identified as gods or spirits, and these gods and spirits were thought to control such things as rain, drought, seasons, and the tides. The first astronomers are believed to have been priests or Magi. The earliest calendars were based upon the phases of the moon and the time between phases.
Western astronomy has its roots in ancient Mesopotamia astrology. The modern practice of dividing a circle into 360 degrees, of 60 minutes each, began in ancient Mesopotamia with the Sumerians.
The oldest astronomical writing that we have is Tablet 63 of the Enuma Anu Enlil. It is called the Venus tablet of Ammi-saduqa. The Venus tablet lists the first and last visible risings of Venus over a period of about 21 years, and it is the earliest conclusive evidence that the phenomena of a planet were recognized.
Since the beginning of time, man has looked up. The sky, particularly the night sky, has been full of mystery that humankind wanted to understand.
The old civilizations of China, India, Greece, and Rome all looked to the stars for explanations to earthly situations and problems, inspiration and guidance. They found all of those things, but they also found knowledge, and over the centuries our knowledge of astronomy has grown. But there are those who believe that we have only just begun to learn all the heavens have to teach us.
Related Topics: Telescope Jargon,
NASA, Guide to Buying a Telescope
|