How Do Telescopes Work - Telescope Lenses

by John B. Mayall

Lenses and mirrors are the elements used to collect and view focused light in telescopes. Mirrors are the medium for focusing in reflector telescopes, while lenses are the medium in refractors. Each type has its own distinct advantages and disadvantages. Refractor type telescopes use lenses. These lenses bend the light when it enters the telescope from the distant object being viewed through it. Because of this refraction it is possible to closely view a distant object. The telescope has two lenses, with one slightly larger.

The eyepiece in the telescope is generally a small lens. Some telescope however, may not use lenses for the eyepiece at all. The eyepiece, in any case, is the most important element of a telescope. It is the element which lets you see correctly whatever it is that you want to focus on. These eyepieces are adjustable and are of a low power. Adjusting the eyepiece allows you to change the magnification factor. What kind of lens you use for the eyepiece is a personal choice. In today's age, several different kinds of eyepieces are available in the market. Because of this motley available, choosing the correct eyepiece fro your requirement may be a difficult task. As a result, you should concentrate on defining the criteria you think are important for your choice. The depth of field, optical quality, sharpness, clarity, brightness, market price, barrel size and how it affects your eyesight are some of the major points of concern. However these criteria always remain individual prerogatives.

Lens designs used in older telescopes go by the name of Huygens and Ramsden. Professional astronomers are advised to not use these lenses anymore as they are not of superior quality, even though they are comparatively less expensive than other market lenses. These lenses also do not provide correction for chromatic aberration or the light circles that form around brighter objects when they are viewed.

Professional astronomers use orthoscopic lenses that are designed specifically for professional stargazing. Even amateurs will find these lenses good for their telescopes. The orthoscopic telescopes use four lenses in the eyepiece, and have a 45 degree field of vision (FOV). Since the eyepiece is the element most important to the quality of a telescope, this design is a winner. The lenses do not strain the user's eyes, and can be used even for viewing closer objects like planets.

For a person with a moderate budget, a Barlow lens is a viable option. The design provides average quality but is a good bargain. It does not burn a hole in one's pocket, and yet is not of inferior quality because of its cost. The range at which this lens is available starts at a low $30 and goes up to $70. The magnification factor is generally not enough for professional use, however for amateurs it should be enough. For hobbyists, it is an ideal lens.

When you're looking for lenses for a telescope, it is important that you determine criteria that most comprehensively fulfill your needs from the lens. Adjustable lenses is a good option as it means you can view objects which are not too far, as well as distant stars with it, and thus obtain the best deal your money can buy you.

About the Author

Download free hubble image space telescope as well as learning more about refractor vs reflector telescopes when you visit http://www.howdotelescopeswork.com, the online portal for free resource on telescopes making and usage

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Illinois - Adler Planetarium - A Great Vacation and Travel Destination

by Robert W. Benjamin

Do you like looking at the stars? If so, and you plan on passing through Illinois, you must stop at the Adler Planetarium. This Planetarium is amazing and it really does have something for everyone. One of the greatest parts about it is there are free daily activities that everyone can enjoy.

There are many different activities that may take place and they do change from time to time. Some of them include hands on science challenges, while others include tours of new exhibits. There are also computer activities, interactive demonstrations, astronomy crafts, and telescope viewing. There are some great activities for kids as young as three, all the way up to adulthood.

Check out how craters are formed and how space rocks impact the earth. Or, check out how gravity works and then move on to the create a comet demonstration. Some people like the cosmic ray detectives class while others enjoy learning more about auroras.

The planetarium is open from Sunday through Saturday from 9:30 am until 4:30 pm. The first Friday of every month has later hours until 10 pm. The holiday schedule changes so it is important to check out the times to know when to visit. The planetarium is always closed on Thanksgiving Day and Christmas Day. During the summer months, there are extended hours as well.

The Adler Planetarium sells tickets only from the box office on a first come first serve basis. For adults the general admission is $10 for exhibits only, $19 for admission and a show, and $23 for admission and two shows. Prices for Chicago residents are two dollars less per package. Kids pay $6 for general admission, $15 for admission and a show, and $19 for two shows in addition to admission. Learn more about space and have fun as an entire family by visiting the Adler Planetarium. It is affordable and has great hours, so make a plan to check it out when you are visiting Illinois.

There is a website that has great information on USA Vacations and Unique Travel Spots Listed State By State and Season, the website is called: Seasonal Vacation Spots, and can be found at this url: http://www.seasonalvacationspots.com

By Robert W. Benjamin

You may publish this article in your ezine, newsletter, or on your web site as long as it is reprinted in its entirety and without modification except for formatting needs or grammar corrections.

About the Author

Robert W. Benjamin has been in the software business on the Internet for over 8 years, and has been producing low-cost software for numerous years. He first released public domain products on the AMIGA and C64 computer systems in the late 1970s-80s.

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Black Hole Facts

by Roger Smith

If you are into science, astronomy or even science fiction, you probably are amazed at the phenomenon called black holes. Black holes by their very name convey mystery and intrigue and while man has theorized about the existence of black holes since the late 1700's, we are still a long way off to knowing precisely what black holes are and how they behave today.

What is a Black Hole? One of the questions most people have about black holes is exactly what they are. Black holes are theorized to be areas of space in which the gravitational field is so strong and powerful that nothing can escape and break passed its grasp. In fact, black holes show up as completely void areas of space, because not even light can escape the strong gravitational forces. It is believed that a black hole is caused by a large star imploding onto itself creating tremendous density and thus incredibly strong gravitation forces.

The Life of a Black Hole Black holes as stated above are caused by a large star- much larger than our own sun imploding. These large stars run out of fuel which is necessary for nuclear reaction. Unfortunately, as the star runs out of fuel, the effect of normally pushing energy out is outweighed by its own gravity which continues to grow exponentially until the star incredibly crushes itself. It crushes itself to such a degree that its mass becomes super dense creating incredible forces of gravity that do not let anything escape its force. It should be noted that a black hole does not last for ever, while it does not allow light to escape, x-ray radiation is emitted and eventually black holes become smaller and smaller till eventually they disappear.

Where are Black Holes Located? One of the most noticeable aspects of black holes is that they usually can be easily located due to the fact that they are completely void areas of space. Black holes have been located throughout our universe in several galaxies. It was theorized that there was even a black hole in our galaxy- the Milky Way, however for a long period of time the evidence was not complete. Recently however, a black hole was discovered in our own galaxy- actually in the center turning many astronomers' theories on their heads.

For more information regarding black holes, the Smithsonian Magazine has a fascinating article on the subject. To read it, please visit our main website.

About the Author

http://www.smithsonianmag.com Smithsonian magazine is a monthly magazine created for modern, well-rounded individuals with diverse interests. It chronicles the arts, history, sciences and popular culture of the times. Each month, expect articles from the Smithsonian Institution's award-winning, monthly general interest magazine, plus exclusive Web articles, videos, blogs, photographs and more.

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Naming Stars in Different Cultures

by Richard Pickering

While modern astronomers refer to most stars solely by catalog numbers and astronomy coordinates, many people informally name stars using name a star services. In fact, throughout history people from various cultures have used star names of their own choosing. Many civilizations explained their existence through mythological stories passed from generation to generation, and often associated these stories with the stars in the night sky. As we'll see, even a major car company is named after the stars.

To illustrate, let's start with a constellation (an area of the night sky) modern astronomers have named after a character from Greek and Roman mythology - "Orion," the Great Hunter. Orion is one of the most well known and easily-identifiable constellations, and can be seen from just about anywhere on Earth: The best time to view Orion is during the evening hours between roughly December and March. Many classical mythology stories are told about Orion and how he came to be placed in the heavens. One such story is that Orion had no fear of any animal and therefore threatened to exterminate all of the animals of the earth. When Gaia, the goddess of the earth, heard this she became enraged and sent a scorpion to kill Orion. When Orion encountered the scorpion he was unable to kill it, and the scorpion stung Orion and sent him falling to the earth, fatally wounded. In honor of this story, Orion was placed in the night sky as a constellation, as was the scorpion - known as the constellation "Scorpius."

While 21st century astronomers refer to the constellation "Orion" after a hunter from classical mythology, other cultures have had different interpretations of these same stars. One of the distinguishing features of Orion is a line of three, bright stars that form what is called "The Belt of Orion." The ancient Egyptians thought these three bright stars were the resting place of the god Osiris. The Dogon people of West Africa viewed the three stars as the stairway to heaven. These same three stars have been associated with Christmas, viewed as representing the Magi - "The Three Wise Men" (The Three Kings) from the Bible. The people of the Marshall Islands viewed Orion's stars as an octopus and a fisherman: The story told was of a fisherman who was attacked by an octopus. The fisherman defended himself by using a stone to stab the head of the octopus. Although the octopus was wounded he was able to spray his ink, behind which he hid and was able to escape. The Chimu Indians of Peru believed that the middle star of Orion's belt represented a thief or mischief maker that the Moon Goddess punished. The Moon Goddess punished the wrongdoer by sending two stars to capture him and send him to four vultures that would eat him. This mythological story served as a warning for those who would commit crimes.

Another interesting example from classical mythology is related to a beautiful group of stars in the constellation Taurus called "The Pleiades," or "The Seven Sisters." These stars are visible in the evening sky from roughly November through April, and are often confused with "The Little Dipper" (which is in another constellation) as the bright stars of the Pleiades together resemble a very small dipper, or ladle. The story from classical mythology is that Orion, the hunter, became enamored of these seven beautiful ladies, and relentlessly pursued them throughout the world. Taking pity on the young women, Zeus placed them in the heavens where Orion continues to pursue them in the night sky.

Many cultures have also associated the Pleiades with females or femininity. The Australian Aborigines saw this group of stars as a cluster of girls who were musicians. These girls play their instruments for a group of young boys who are represented by the stars seen in Orion's belt. Some Native American tribes viewed the Pleiades as seven mothers who were looking for their seven lost sons: According to the Chumash Indians of California, these seven sons had become the stars of the Big Dipper. The Kiowa Indians saw these stars as young women who were placed in the heavens by the Great Spirit so as to save them from attacking bears. In Norse mythology, they were the hens of Freya, the goddess of love, beauty and fertility. In Japan the Pleiades were known as "Subaru," after which a Japanese car company is named.

Naming stars, then, is an age-old custom that has been practiced by different civilizations around the world.

About the Author

Richard Pickering is an astronomer for Name A Star Live. While no star-naming service can change the scientific designations of stars, only Name A Star Live makes it real by providing you: Virtual Planetarium™ astronomy software; an opportunity to view your star live using an online telescope; and the launch of your star name into space!

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