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The Hubble Space Telescope
Telescope Accessories
When you purchase a telescope -- any telescope -- what you get is…well…a telescope. You don't get anything else, and there are a few "accessories" that really shouldn't be considered accessories.
For example, you really, really need a mount for your telescope. Telescopes need to remain perfectly still while you are observing the heavens. Even the slightest movement isn't satisfactory. It is impossible to hold a telescope perfectly steady, so when you buy your telescope, you also need to buy a mount.
There are basically two types of telescope mounts to choose from: altazimuth and equatorial. The mount that will best serve your needs depends upon how and who will use it. There are two things that you need to remember no matter how much information you gather.
1. Astazimuth mounts cost less that equatorial mounts and they are easier to operate.
2. Equatorial mounts are more expensive than astazimuth mounts, are more difficult to operate, and have many more controls.
Slow-motion controls are another "extra," and both astazimuth and equatorial mounts can be fitted with them.
Filters are another "essential" accessory. For the beginner, just three filters will do; a solar, a lunar, and a light-pollution filter.
A solar filter will cost between $30 and $150 depending upon the filter you choose. Basically, a solar filter allows a user to observe the sun and sunspots because it allows only a small fraction of the sunlight to pass through it. Mylar filters (less expensive) cause the sun to appear as a light-blue color, while glass filters (more expensive) leave the sun in its natural yellow-orange color.
A lunar filter is not expensive, and if you want to observe the moon in any phase other than the first quarter, you need one. A lunar filter will cost about $20.
If you live in a metropolitan area, you most definitely need a pollution filter if you intend to look at deep sky objects. Pollution filters cost between $60 and $150, or even more.
See Also:
Galaxies
Mirrors and Lenses
The Zodiac
The zodiac is a cycle that covers a year's time. There are several versions of the zodiac system. There is a Babylonian zodiac, an Indian zodiac, a Chinese zodiac, a Western zodiac, and several others. All of the various zodiacs are basically the same. They are all based upon the constellations and they all contain 12 stations, or signs.
The Western zodiac is the one that is mostly used in the United States. Modern Western astrological signs are really just simplifications of the signs used in Hellenistic times.
In the list below are the Roman names for the signs of the zodiac, their ecliptic longitudes of their first points, the symbols that represent them, and the associated dates:
Aries: 0°, the Ram, March 21 to April 20
Taurus: 30°, the Bull, April 20 to May 21
Gemini: 60°, the Twins, May 21 to June 21
Cancer: 90°, the Crab, June 22 to July 22
Leo: 120°, the Lion, July 23 to August 22
Virgo: 150°, the Virgin, August 23 to September 22
Libra: 180°, the Scales, September 23 to October 23
Scorpio: 210°, the Scorpion, October 24 to November 22
Sagittarius: 240°, the Archer, November 22 to December 21
Capricorn: 270°, the Sea-goat, December 22 to January 19
Aquarius: 300°, the Water Carrier, January 20 to February 18
Pisces: 330°, the Fish, February 19 to March 20
Sidereal zodiac astrology (used mostly by Indian astrologists) dates are different from the tropical zodiac astrology dates. However, the tropical zodiac dates are the ones that are used primarily in the West.
Astrology is not an exact science (if you think of it as a science). All of the implications of certain signs and the position of certain planets are open to interpretation. Different astrologists will give different readings based upon the same information.
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More articles:
The Carl Sagan Portal
HubbleSite -- Out of the ordinary...out of this world.
Quotes from famous scientists
Hubble Space Telescope
SOLAR ECLIPSE: Stories From the Path of Totality
Guide to Buying a Telescope
Our Solar System
Our solar system consists of our sun, eight planets, the 166 known moons that orbit these eight planets, 3 dwarf planets and the four known moons that orbit them. Our solar system also includes billions of other small bodies such as asteroids, Kuiper belt objects, comets, meteoroids, and interplanetary dust.
In short, our solar system is made up of our sun and all the celestial objects that are gravitationally bound to it.
The general outline of our solar system is (from the center outward):
1. The sun
2. Four terrestrial inner planets (Mercury, Venus, Earth, and Mars)
3. An asteroid belt (made up of rocky objects)
4. Four outer planets (Jupiter, Saturn, Neptune, and Uranus)
5. The Kuiper belt (made up of icy objects)
6. Scattered disc (poorly understood region)
7. Heliopause (where the sun's solar wind is stopped by the interstellar medium)
8. And finally, a hypothetical Oort Cloud (there is a lot of ongoing debate about the Oort Cloud).
Yes, there was another planet called Pluto, but it is no longer considered a planet. Back in August 2006, the International Astronomical Union (IAU) in Prague decided that Pluto did not meet the requirements to be designated a planet, and it is now classified as one of many dwarf planets.
In the dim and dusty past, it was believed that the Earth was the center of the universe and that everything else revolved around it, including the sun. That theory changed as knowledge was gained. The telescope was invented, and men could see farther and farther.
The formation of our solar system remains a basis of contention between some religious leaders and some scientists. There are some of each who believe that God created the universe in six days, just the way creation is described in the book of Genesis in the Bible. There are others who subscribe to the "Big Bang" theory. The debate has been raging for decades and shows no signs of abating. But however our solar system came into being, it is magnificent!
Related Topics: Our Sun's Twin,
Our Solar System, About Telescopes
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