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Technology Of Telescopes: Explained.


A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).
 The first known practically telescopes were invented in the Netherlands at the beginning of the 17th century, by using glass lenses. They found use in both terrestrial applications and astronomy. Within a few decades, the reflecting telescope was invented, which used mirrors to collect and focus the light. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. 



The word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.



Now technology has advanced so much that so many private companies has came forward with innovating technology in the field of Digital Telescopes and Sloohis the top among those companies.



Slooh, a Connecticut-based company, makes it easy and now free to look at the night sky through any one of dozens of telescopes around the world. To use the service you simply log in and pick a telescope. If you want to take control you can begin to point the telescope at various spots in space or you can simply go along for the ride while a professional astronomer takes the reins. Slooh users even share discoveries they find while peering into space.

In honor of the upcoming eclipse the service is offering free accounts to folks who want to watch the lunar eclipse remotely. You can sign up now for a free account or pay $4.95 a month to be able to control the telescopes. So what's the technology used behind a Telescope, normally its a vessele with glasses and lenses arranged, right? Bus is that all? Is there something much bigger innovation used? Let's have a look:



The name "telescope" covers a wide range of instruments. Most detect electromagnetic radiation, but there are major differences in how astronomers must go about collecting light (electromagnetic radiation) in different frequency bands.

Telescopes may be classified by the wavelengths of light they detect:

X-ray telescopes, using shorter wavelengths than ultraviolet light
Ultraviolet telescopes, using shorter wavelengths than visible light
Optical telescopes, using visible light
Infrared telescopes, using longer wavelengths than visible light
Submillimetre telescopes, using longer wavelengths than infrared light
Fresnel Imager, an optical lens technology
X-ray optics, optics for certain X-ray wavelengths


Raw Materials Used For Making A Telescope:

A telescope consists of an optical system (the lenses and/or mirrors) and hardware components to hold the optical system in place and allow it to be maneuvered and focused. Lenses must be made from optical glass, a special kind of glass which is much purer and more uniform than ordinary glass. 

The most important raw material used to make optical glass is silicon dioxide, which must not contain more than one-tenth of one percent (0.1%) of impurities. Optical glasses are generally divided into crown glasses and flint glasses. 

Crown glasses contain varying amounts of boron oxide, sodium oxide, potassium oxide, barium oxide, and zinc oxide. Flint glasses contain lead oxide. The antireflective coating on telescope lenses is usually composed of magnesium fluoride.



A telescope mirror can be made from glass that is somewhat less pure than that used to make a lens, since light does not pass through it. Often a strong, temperature-resistant glass such as Pyrex is used. Pyrex is a brand name for glass composed of silicon dioxide, boron oxide, and aluminum oxide. 

The reflective coating for telescope mirrors is usually made from aluminum, and the protective coating on top of the reflective coating is usually composed of silicon dioxide. Hardware components that are directly involved with the optical system are usually manufactured from steel or steel and zinc alloys. Less critical parts can be made from light, inexpensive materials such as aluminum or acrylonitrile-butadiene-styrene plastic, commonly called ABS.


The Manufacturing Process:

Making the hardware components:

Metal hardware components are manufactured using standard metalworking machines such as lathes and drill presses.

Components made from ABS plastics (usually the external body of the telescope) are produced using a technique known as injection molding. In this process the plastic is melted and forced under pressure into a mold in the shape of the final product. The plastic is allowed to cool back into a solid, and the mold is opened to allow the component to be removed
.

Making optical glass:

The glass manufacturer mixes the proper raw materials with waste glass of the same type as the glass to be made. This waste glass, known as cullet, acts as a flux; that is, it causes the raw materials to react together at a lower temperature than they would without it. This mixture is heated in a glass furnace until it has melted into a liquid. The temperature needed to form molten glass varies with the type of glass being made, but it is typically about 2550°F (1400°C).

Making the lenses:

The blanks are processed by the telescope manufacturer in three steps: cutting, grinding, and polishing. A mirror is formed in exactly the same way as a lens until the reflective coating is applied. First a high-speed, rotating cylindrical cutter with a round diamond blade, Telescope known as a curve generator, shaves the surface of the lens until a close approximation of the desired curve is achieved. The cut lens is inspected with a spherometer to check the curvature and is recut if necessary. The time required for cutting varies greatly with the type of glass being cut and the kind of lens being shaped. A lens may require several cuttings, each of which may take anywhere from a few minutes to more than half an hour.

Applying coatings:

To make a lens into a mirror, a very thin, very smooth coating of aluminum is applied. Aluminum is heated in a vacuum to form a vapor. A negative electro-static charge is applied to the surface of the lens so that the positively charged aluminum ions are attracted to it. Similar procedures are followed to apply a coating of silicon dioxide to protect the fragile surface of a mirror or to apply an antireflective coating of magnesium fluoride to the surface of a lens. The finished lens or mirror is inspected, labeled with a date of manufacture and a serial number, and stored until needed.

Assembling and shipping the telescope:

The hardware components, lenses, and mirrors required to make a particular model of the telescope are assembled by hand in an assembly line process. The completed telescope is packed with close-fitting expanded polystyrene foam to protect it from damage during shipping. The telescope is packed in a cardboard box and shipped to the retailer or consumer.

How Do Telescopes Work?

There are two basic types of telescopes, refractingand reflecting. Refracting telescopes use lenses to focus the light, and reflecting telescopes use mirrors. I’ll talk first about refracting ones.

Refracting telescopes work by using two lenses to focus the light and make it look like the object is closer to you than it really is. Both lenses are in a shape that’s called 'convex'. Convex lenses work by bending light inwards (like in the diagram). This is what makes the image look smaller. The biggest refracting telescope in the world is located at the Yerkes Observatory of the University of Chicago at Williams Bay, Wisconsin. It has an objective lens that’s 1.02 meters (40 inches) across, and it’s total power is 195x.



Reflecting telescopes, on the other hand, don’t use lenses at all. Instead, they use mirrors to focus the light together. In this case, the type of mirror that they use is a concave mirror. Mirrors of this shape also accomplish the goal of bending light together, except that they do it by reflecting the light instead of bending it as it passes through (like lenses do).

 The problem with these telescopes is that in order for a person to see the image at the focal point, the telescope has to be so big that a person can actually sit in the middle. (Or they have to put a small mirror in the middle to reflect the image out the side of the telescope, instead.) This is why the reflecting telescope built in the 1780’s by the famous astronomer William Hershel was so big:



Some more complicated telescopes work by combining both lenses and mirrors, but there are so many different ways of doing this that I’m not going to try to get into them. The other way you may have heard of telescopes being categorized is by what kind of light they pick up, rather than how they work. This is what they’re talking about when they say things like , which are still made by some combination of refracting and reflecting.



Frequently Asked Questions:


Q.Why is your eye, so bad at seeing things far away?
A. Human eyes can see long distances. In fact the Andromeda Galaxy can be seen with the naked eye and that's 2.5 million light-years away. But even a massive galaxy, like Andromeda, appears to us as a tiny point in the sky. It makes sense that as an object gets further away it becomes harder to see. But why this happens helps us understand how vital telescopes have been in exploring the universe.

Q.Do bigger lenses give us a bigger image?
A. To make a distant object appear brighter and larger, we effectively need a bigger eye to collect more light. With more light we can create a brighter image, we can then magnify the image so that it takes up more space on our retina. The big lens in the telescope (objective lens) collects much more light than your eye can from a distant object and focuses the light to a point (the focal point) inside the telescope.

A smaller lens (eyepiece lens) takes the bright light from the focal point and magnifies it so that it uses more of your retina. A telescope's ability to collect light depends on the size of the objective lens, which is used to gather and focus light from a narrow region of sky. The eye piece magnifies the light collected by the objective lens, like a magnifying glass magnifies words on a page. But the performance of a telescope depends almost entirely on the size of the objective lens, sometimes called the aperture.

Q.What's the big problem with refracting telescopes?
A. If you've ever seen light bend through a prism you probably have an idea of where the problem lies with a refracting telescope; it's the lens. When light travels through glass it slows down, that's why it bends. Lenses are shaped perfectly to bend light in particular ways. But the amount light bends depends on the wavelength, or colour, of the light.

White light is a mixture of all colours, from red to violet. Red light bends the least and violet light bends the most. When white light travels through the objective lens, the different colours bend at different angles and are focused at slightly different points. Different coloured images are misaligned creating a blurry image with fringes of colour along the boundaries that separate dark and bright parts.

Q.Can telescopes with mirrors correct the problem?
A. Reflecting telescopes magnify distant objects using the same principle: more light is collected and focused to a point and this is magnified so that it fills your field of vision. But instead of using a lens, a curved mirror (primary mirror) collects the light and reflects it to a focus. Because light doesn't pass through the mirror, it doesn't bend the different colours by different amounts, the way a refracting lens does.

A small mirror (secondary mirror) is placed in the path of light from the primary mirror to reflect the image towards the eyepiece. The secondary mirror must be very small so that it doesn't block the light from the distant object as it travels to the primary mirror. Another benefit of using mirrors instead of lenses is that big mirrors are easier and cheaper to make than big lenses. Reflecting telescopes can be much larger and therefore look deeper into space.

This is just a small description of a vast topic, still i hope this thread helps some of you to get a idea about Telescope and its working. Please do provide your valuable feedback and suggestions as REPLIES below.

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