Wednesday, July 30, 2008

How Do Telescopes Work - Amateur's guide to Telescope-making

by John B. Mayall

When Galileo made his telescope, he was far from the expert he became later. He was just a layman, who found the sky and its stars fascinating and wanted a device that would take him closer to the object of his fascination. It was this desire that led him o devise the first ever telescope that changed the face of history in more ways than we can imagine.

In today's age, a person is able to buy a telescope, readymade, from the market. But for one who is not experienced, constructing a telescope is akin to an adventure. Although the procedure is complex and technical, and quite long, it is quite possible to make a telescope for oneself, by oneself. For the amateur who holds a keen interest in the telescope and the way it works, constructing it by oneself can be quite adventurous and fulfilling.

The construction itself is not very difficult, and it is made easier if one can enlist the assistance of another person who has himself constructed telescopes earlier. Even someone who is an amateur astronomer would make a good mentor, if it's no possible to find one experience in telescope construction. Astronomy clubs generally have at least one member who has prior experience of building telescopes, and such people are quite accommodating towards amateurs.

For an amateur, telescope construction can be a cumbersome task. Patience and calm are advisable for a first-timer. The greatest inventions of all time came from blind experiments and unexpected results. When starting out, it is always best to have some references and manuals handy, as they can explain the technical aspects in the clearest ways. A local library is a good source for material to an amateur just starting out in telescope building.

The basic elements of a telescope are the mirror, two lenses, the housing for the whole structure, and materials that will be used for polishing the mirror. These parts can all be bought at local stores or even online. The mirror can be ground at home as well, but is a tiresome process.

The construction of a telescope is a long and drawn out process. Careful planning is required to ensure that there is minimal cleaning up left after all the work is completed. Is advisable to lay out newspapers to ensure clean work as well as to ensure correct placement of all the equipment. Maintain a logbook if possible to keep track of the task completed and the duration of each task. In later stages, the logbook is a good record to refer to understand the tasks completed and how long each task required. Also, it helps one to remember what work has been completed and what remains.

Once the construction is complete, it is quite natural for the amateur to be pleased with himself for the work he has accomplished. It is however, easier to buy a telescope kit from the market instead of purchasing individual component and constructing the whole structure. Assembling a telescope from a kit is easier, takes less time and is a better financial option. Such telescope kits are intended for the amateurs, and not directed at the professionals.

About the Author

Get free lessons on how to build a telescope as well as professional advice on how to buy a telescope when you visit, the premier portal on how to use telescopes.

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Friday, July 18, 2008

Choose a Good Beginners Telescope - Cut Through the Information Overload

by Aidan James

So you've been bitten by the astronomy bug and want to get started with your very own telescope, but you're confused by the vast number of possible purchases? You are not alone, astronomy stores are accustomed to dealing with the confused beginner though of course not everybody has the opportunity to visit a specialist store. This article is intended to help cut through some of the confusion.

It's important to choose a telescope that is right for you, for example there is no point having a great big Dobsonian if you rarely get the chance to assemble it in a good dark sky location.

There are several factors to be considered from practical considerations like size, weight and portability to the price you can afford and indeed where you'll be doing the majority of your observing. Ignoring more advanced uses like astrophotography we might think along the following lines.

As a general rule, the larger the aperture the more you can expect out of your telescope. Refractors will generally outperform similar size reflectors. Refractors however are more expensive than reflectors, due to the extra high quality glass involved. They can also be impractical to handle at larger apertures where they can also reach very long tube lengths.

Large aperture reflectors can have comparatively short tubes and be very easy to handle as well as inexpensive. There is a little extra maintenance involved as you may need to clean and align the mirror from time to time, this procedure is known as collimation.

Catadioptric telescopes are a combination of refractor and reflector and are quite portable even at large apertures. A great many amateur astronomers who have access to good dark sky sites, ultimately end up with catadioptric telescopes because the offer a range of possibilities including astrophotography. The large ones, like most large aperture scopes, are not ideal in light polluted areas like the city and suburbs.

Those big Dobsonian telescopes are really just big reflectors mounted on simple turntables and their attraction is their huge light capture and simplicity of use, making them ideal for visual astronomy in a good location (again they are not so good in light polluted areas).

If you do not relish the thought of learning to find your way around the skies you could consider purchasing one of the models that come with a computerized mount. These 'Go-To' telescopes have made finding targets a breeze.

With those facts in mind you can now think about where you are going to do the most observing and choose a suitable beginners telescope. If you live in the city and are unlikely to get to a rural location for observing then perhaps stick with the small to medium size refractors, reflectors or catadioptrics, with or without the go-to function, your budget will probably start to dictate the choices here! If on the other hand you live in a dark sky area then my recommendation is to buy a great big Dobsonian. These offer so much viewing pleasure and are so simple to use it is difficult to fault them.

About the Author

See my Squidoo page for more on how to choose a good beginners telescope and some specific recommendations and absolute bargains! Telescopes for Beginners, a site helping others get a start in astronomy. Telescopes for Beginners

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Monday, July 14, 2008

Binoculars For Astronomy - Know the Basics

by Aidan James

If you like to look to the heavens even just occasionally get yourself some decent binoculars and indulge in a little binocular astronomy. Think about it, binoculars are inexpensive, highly portable and require no complicated setting up procedure so are ideal for casual astronomy.

Binoculars allow excellent moon views, and great viewing of star fields, comets and even deep sky objects. They are especially useful for beginners as unlike astronomy telescopes they keep the view the the right way up, making it really easy to navigate the skies. With a little practice you can pick out several of the planets and even the larger moons orbiting Jupiter. Clusters like Pleiades look great because the binoculars wide field of view lets you have more of the cluster in view at one time than a telescope would.

So how to choose which ones? Binoculars have two specifications marked on the body of the binocular in the form of 7x 50, where the first number represents the magnification (in this case 7 times) and the second the aperture in millimeters (50mm in this case). When it comes to selecting the right binoculars for astronomy, aperture is the most important feature to think about. The bigger the aperture the more light is captured so the brighter and clearer the image will be. For astronomy use you will need at least 40mm aperture and preferably larger.

You will need a magnification factor of at least 7, maybe up to 10 if you have a steady hand. Any higher than about 10 times magnification and you will need to mount your binoculars on a tripod as the hand shake effect makes it difficult to get a sharp image.

There are giant binoculars available with higher magnifications and apertures which are designed for astronomy use but you will certainly need a sturdy tripod or mount to use them. These can offer excellent viewing up to about 25 times magnification with 100mm apertures.

This brings us to another point, a specification known as the 'exit pupil'. This specification refers to the diameter of the shaft of light that exits the eyepieces and into your eyes. You can easily calculate it by dividing the aperture by the magnification so that 7 x 50 binocular has an exit pupil of just over 7mm. Capturing as much of that as possible is good as it means all the available light is getting to where you want it, i.e.your eye. If you are still in your twenties you can probably use all of that 7mm exit pupil mentioned above as your pupils will dilate to about that size in very dark conditions, however as you get older your pupil does not dilate more than about 4 to 5 mm so large exit pupils are wasted (though it starts to make those 25x 100's look good!).

You might notice another specification marked on the binocular, the field of view (FOV), it refers to the apparent side to side view as you look through the binoculars. It will be expressed as an angle in degrees or a measure such as 340 feet at 1000 yards. For astronomy use we can generally ignore that factor, it really does not matter a great deal at the distances we'll be viewing at.

So now you have the basics why not get yourself some binoculars and indulge in a little casual astronomy, you'll be rewarded with some wonderful sights!

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Galileo's Telescope

Galileo Galilee used a basic version of the telescopes that are used widely today. Galileo used a refracting telescope and used two lenses, a concave and a convex lens inside a tube. Convex lenses have edges that curve inwards. That's what the typical magnifying glass uses. Concave lenses, on the other hand, have lenses that curve outward. Some believe that the spy glasses, which were invented earlier and made popular around the same time, inspired Galileo to make his own telescopes.

When the convex and concave lenses are combined together, they are able to magnify distant objects. This is the main principle behind the refracting telescope. These lenses gather and focus light at a point. When light that is collected bends and forms images, refraction takes place.

Galileo used his telescope to view the moon and planets like Jupiter and observe them in detail. Although the images were not sharp, he still was able to draw the moon with its craters. To improve the optical quality of his telescopes, he made his own lenses and was able to achieve a magnification of 9x using them in his telescopes. Today, variations of refracting telescopes exist. The special combination of lenses now make it possible to use a short tube for refracting telescopes. Telescopes have come a long way since Galileo.

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Sunday, July 13, 2008

All About The Stars

by Dave Clark

We all love gazing stars in the sky but do we know as to what are these stars made up of and how they are born. Well, there are lot many questions surrounding the stars. So, let us begin with their formation. Stars are basically made up of plasma. Nebula is a term often used in this regard. It basically refers to the assemblage of dust particles and gas and when all these dust particles and gases get together, they form a star.

Did you know that sun is also a star? It might appear strange to you, but yes sun is also a star which appears to be bigger than rest of the stars but is actually smaller in comparison to others. Not only that, it also has a much less quantity of mass as compared to others. This is the reason why it has been able to survive for so long. After knowing this fact, you must have come to know that mass of the star is inversely related to its life cycle; the more the mass a star has, the lesser will be its life span and vice versa.

Let us now discuss the life cycle of a small star of about one solar mass. It passes through different stages of life. As mentioned before, when nebula is available in high density, it leads to the formation of a star. After that, it condenses to form a huge blob of gas and ultimately contracts under its own gravitational force. As the star becomes hot, it glows in the sky and transforms into a protostar. If it has adequate substance, it attains a very high temperature of 15 million degrees centigrade. At this heat level, nuclear reactions take place, thereby causing fusion of hydrogen. This in turn gives rise to helium. At this stage, the star starts releasing energy and shines all the more. It is now called the main sequence star.

A small star stays into the main sequence stage till the entire hydrogen converts into helium. In the next stage, the helium core begins to shrink. When the core becomes extremely hot, it causes fusion of helium to form carbon. This leads to the expansion of its outer layer. After some time, it becomes cool and glows. The expanded star is popularly called red giant. After a certain period, the helium core vanishes and its outer layer goes away from the star in the form of a gaseous shell. The left core turns into a white dwarf and fades away. Then a stage comes when the star stops glowing and is called a black dwarf. So, this is the life cycle of a star.

About the Author

Dave Clark is a freelance article writer and has been in the industry for many years, he has written many books and is very knowledgeable in various fields, Dave also works for Cushy Sofa a supplier of memory foam mattresses, sofas and Divan sets.

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