|
Carl Sagan
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:
New Astronomy Video
Planting by the Moon
The Stars
Our sun is a star. It is one of the billions of stars in the Milky Way Galaxy. On a clear night, when you look up at the sky, you can see thousands of stars with your naked eye. If you have a pair of binoculars or a telescope, you can see more stars than you could ever hope to count.
Each star is unique, but they all share things in common as well. Stars are born from interstellar gas clouds, nuclear fusion causes them to shine and stars die. Sometimes the death of a star is a very dramatic event.
Cold interstellar clouds or nebula, like the Orion Nebula and the Eagle Nebula, are the incubators and nurseries from which stars are born. An extremely simplified description is that gravitational collapse happens and forms a rotating gas globule. The resulting globule spins faster and faster. The central core becomes a star while the other material becomes planets or asteroids.
The life of a star begins and ends with a battle between two forces: gravity and pressure. It takes energy for a star to live, and this energy comes almost entirely from nuclear fusion of lighter elements into heavier elements. This is the energy through which a star can shine for millions or billions of years.
Stars fuse hydrogen to helium for most of their lifetime. This is referred to as the "main sequence" of a star's life. Our sun, Vega, Sirius, and Spica are all stars that are in their main sequence. Once the hydrogen in the core of a star has been used up, the star becomes a red giant like Betelguese, Arcturus, Aldebaran and Antares.
A star's life is limited because the hydrogen at the core is not self-replenishing and will eventually be used up. A star cannot depend upon thermal energy to resist the pull of gravity forever, and a star's final fate depends on whether something other than thermal pressure manages to halt the relentless crush of gravity. |
|
More articles:
Neptune - Wikipedia, the free encyclopedia
Astronomy Clubs world wide
Ham the Chimp - Wikipedia, the free encyclopedia
Petition to put Carl Sagan on a stamp
Ham the Chimp Takes A Ride Into Outer Space - 1961
Nicolaus Copernicus
Planting by the Moon
Ah, the moon! The moon has been studied by astronomers (both professional and amateur) for centuries. We even reached out and touched it when Neil Armstrong stepped onto the moon 1969. The moon has been the subject of songs, movies, and poetry, and probably always will be. Astronomers have always been utterly fascinated by the moon, and mankind has been fascinated by how it affects the earth and earthlings since time began.
We do know without a doubt that the moon regulates the ocean tides. It is also a certainty that sleeping with moonlight on your head will not turn you into a werewolf or drive you insane. Some beliefs about the moon have been proven true while others have been proven not true.
Farmers have planted according to the moon for centuries, and more and more farmers are returning to those moon-planting axioms every year. Why? Because they work. Planting root vegetables when the moon is "waning" will produce more root vegetables like potatoes, carrots, turnips, beets, etc. Planting vegetables when the moon is increasing will produce more vegetables that produce above ground (beans, peas, lettuce, tomatoes, etc.).
Planting and gardening by the moon gets even more specific. For example, it is better to turn soil when the moon is in the last quarter. The moon tells farmers and gardeners when it is to their advantage to plant, as well as when it is to their advantage to pull weeds or turn soil.
There are many who doubt the validity of planting by the moon, but consider that the moon does have an effect on humans (you can get a lot of debate about that statement). We don't fully understand everything we know about those effects yet. You can ask any policeman, clergyman, doctor, or nurse and they will tell you that during a full moon, there are more crimes committed, more suicides, and more babies born.
Related Topics: Solar Eclipses,
NASA, Astrology Beliefs
|