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Telescopes

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How Telescopes Work

A telescope is a device that allows us to bring distant objects closer to us so
that we can study them. A good example is the many planets, galaxies, and stars
in outer space. Some range from $1 at the toy store to the $1.2 billion Hubble
Telescope. There are two types of telescopes. Refractors use a glass lens.
Reflectors use mirrors instead of a lens.

Let's take the different pieces of a microscope and see how they work. The
objective lens in a Refractor or primary mirror in Reflectors gather incoming
light and brings it to a focus. The eyepiece takes that same light and
magnifies it to take up a large part of the retina of the eye. Thus, it takes a
small image and spreads it out to make it look bigger.

There are two general principles to any telescope. One is how well it can
collect light. The other is the magnification of the image you are viewing.
Collecting light is related directly to the diameter of the lens. The more
light collected, the brighter the image.

Magnification is the ability to take an object as a far distance and enlarge it
so you can see it clearly. Any magnification can be obtained by using different
eyepieces depending on the object you are trying to view.

Here is a simplified explanation. Obtain two magnifying glasses and a piece of
paper. Hold one of the glasses between you and the paper. At this point, the
image will be blurry and unreadable. Take the second glass and place between
your eyes and the first glass. Moving the second glass up or down should bring
the piece of paper into view. It will be larger and upside down though. Give it
a try and see what happens.

Viewing the Night Sky with a Telescope

Depending on the type of telescope you have purchased, you should be able to
see many wondrous images with it. You might see the moon's surface, the moons
of Jupiter, or even Saturn's rings. With some knowledge of the sky and
constellations, you may be able to pick out some star clusters.

The best way to get your hobby going is to join your local astronomical
society. They will sometimes have telescopes you can borrow to get the hang of
using one before you buy. They also meet in the evenings so you can learn how
to observe the night sky. It is truly fascinating to see the images with your
own eyes instead of just looking at pictures on the web or in books.

Telescopes are used for two reasons. One is to see fainter objects and the
other is to magnify images far away. You must discern which focal ratio is the
best for what you are trying to see. A focal ratio is the ratio of the focal
length to the aperture. Usually starting around f/8 is good for beginners.
Going below f/8 will give you wider, brighter views, but image quality will be
lower. Going above f/8 is usually saved for viewing the moon and planets and
deep sky objects such as galaxies or nebulae.

To get started, just set up your telescope and start looking into the night
sky. There is no telling what you might see. You can look at the moon every
night for a year and still not see everything it has to offer. The same is true
for the entire Milky Way galaxy. There really is no limit to what you can find.
Another neat thing to do is to count sunspots which provide a gauge of solar
activity. Be sure to have the proper filter. Just have fun and see what you can
find.


Using a Telescope

So you have gone out and bought a telescope and have no idea what to do with
it. Go out into the night sky and look for the brightest objects you can find.
They are the best to start with because they are easy to find. Then after that,
the sky, quite literally, is the limit.

With a special filter, you can see the sun and count sunspots. Observe the
milky way or the moon. The moon has many large craters and you may see "rays"
coming out from them. These are from when a crushed rock exploded from meteor
impact. Streaks are formed in a radial pattern out from the crater itself.

Jupiter can be quite interesting to observe at night. It is one of the most
easiest to find besides the sun and moon. Some small telescopes might even get
a good picture of Jupiter's small satellite moons. They are usually in a
straight line and appear as very bright stars. Given Jupiter's rapid rotation,
you can view nearly all the planet in a single night.

The simplest thing you can do is look at the stars. Sometimes, you may see a
"double-star." What looks like a single star becomes two when using a
telescope. These are quite popular because of the explosion of color you will
find between the two of them.

Charles Messier was a comet hunter. One day, he noticed some fuzzy objects that
didn't appear to be moving. These were actually the nebulae of today. Some
people think it is fun to take a single night and see how many deep sky objects
you can find on Messier's list in a single night. There are 110 you can find.

The important thing is to have fun and spot the brightest stars first and go
from there. This can be a rewarding hobby after you have had time to get used
to the telescope and what it can do.

Basic Tips for Using Telescopes

Telescopes tend to come in two different types -- Reflectors and Refractors. A
Reflecting telescope is good for looking at galaxies and starclouds, and they
allow the observer to see sharp images. They are also less expensive than
refractors because they usually have just one surface that helps to focus the
light.

Refracting telescopes can be used to view stars and planets, but they are quite
expensive. These types of telescopes are usually in the form of a long tube with
an eyepiece on one end and the lens at the other end.

Perhaps the best way to start is with a pair of binoculars. They are quite
portable and have a wide field of view. They are also less expensive than a
telescope and they can be used for other purposes as well. Comets have been
discovered by people using binoculars. In fact, did you know the binoculars you
have packed away in the closet at home are more powerful than Galileo's first
telescope?

You don't need motors to drive the telescope either. After a bit of playing
with it, you will be able to guide the scope by hand to where you want to look.
You only need a motor if you are trying out astrophotography.

Make sure your tripod is mounted firm. You don't want it falling over while
you're focusing on a particular star. The simplest telescope out there is
called a Dobsonian Reflector telescope. It sits on a "Lazy Susan" type of mount
and is very affordable.

Finderscopes are good to have on your telescope as well. This is a smaller
telescope that is mounted next to the eyepiece. This piece of telescope
equipment will make finding your specific object easier.

Try out different telescopes and equipment and see what works best for you. If
you want to try it before you buy a complete set, consider buying a used
telescope. There are all kinds of options out there for your particular viewing
pleasure.

Different Types of Telescopes

From the Greek tele which means far and skopein which means to see, a telescope
helps us to see the remotest of objects. Whether they be 50 feet away or in
another galaxy, telescopes have been around since the 1600's to aid us in
viewing the fascinating space all around us. There are as many different
telescopes as there are reasons to use them. The most common ones are mentioned
here.

Parabola shaped radio antennae are called Radio Telescopes. They are built from
large groups of dishes that are made of a conductive wire mesh. As of 2005, the
array sizes is many times larger than the width of the Earth.

Optical telescopes focus light mainly from the visible end of the
Electromagnetic Spectrum. They can increase the size of distant objects as well
as their brightness. These scopes employ mirrors or certain types of lenses to
gather light and focus it. A good example would be a pair of binoculars.

X-ray or Gamma-Ray telescopes have rays that go through many glasses and
metals. The mirrors involved in these scopes are usually parabolic in shape.
Gamma-ray scopes don't even try to focus, they use a specific code to tell them
what the shadows they are looking are. These scopes are usually found orbiting
the earth.

Refracting telescopes are the ones that are most common. They are usually made
out of a long tube that has a piece of glass at one end and he eyepiece at the
other. These were what the pirates used when looking out into the distance.

Reflecting telescopes were developed by Isaac Newton. Where refracting
telescopes used a lens, reflecting telescopes used a mirror to capture light
that was placed in the very back of the telescope. These scopes offer a bigger
view and bright wide view of comets and star clusters.

Eyepieces for Telescopes

Beginner astronomers need to be careful with these items as they tend to go way
overboard. There are various designs and different lenses for different
viewings. You need to figure out what you will be looking at and go from there.
You may need two to three different eyepieces, but no more than that. Here is a
simple guide to the different eyepieces and cost involved.

The most popular is the Plossl. It uses four to five elements and have a wider
field of view than Orthoscopic lenses. It usually ranges from 50-52 degrees.
They run between $50-$150.

For general use, the Orthoscopic lenses were considered the best. They use four
elements and are good for planetary viewing. They have a 45 degree field of
view. They run between $40-$100.

The Kellner is a general purpose lens. It has a three element design and a
40-45 degree field of view. They run between $30-$50.

The Ramsden and Huygenian are good solar lenses. They have two element designs.
They are supplied with the least expensive telescopes and have very narrow
fields of view. They cost between $25-$40.

Barlow lenses are a great piece to have. They can double or triple the
magnification of your eyepiece. They run between $60-$100.

Erfles are not as favorable today. They use six elements and and a 60-65 degree
field of view. They run between $75-$150.

Televue has come out with some designs for eyepieces. The six element Panoptic
has a 67 degree field of view. It runs between $200-$400. The other is a seven
to eight element Naglers. This lens has an 82 degree field of view and runs
between $175-$425.

Pentax also makes a seven element lens, the SMC-XL, that runs around $250 each.
It is thought that these exceed the what th Televues can do.

Telescope Advice for Beginners

You have taken the plunge and purchased a telescope. Now what do you do with
it? Astronomy can be a wonderful hobby, but here are some tips to make sure you
get started on the right foot, or star as the case may be.

Look up the night sky without the aid of a telescope. Can you spot and name any
constellations? Can you spot the moon or the planet Venus or Jupiter? If you
can't do this, you might have some trouble spotting other heavenly objects.

There are many magazines out there that follow astronomy and can give you
sample pictures and sky charts to go buy. The most common are SKY, TELESCOPE,
or ASTRONOMY.

Join an astronomy group or a star watching society. These groups usually have
telescopes you can borrow for a look to see if it is really what you want. They
also have advanced members who can teach you where to look for certain objects.

As any experienced astronomer will tell you, a pair of good binoculars can
become your first telescope. They are relatively affordable, and if you decide
astronomy isn't for you, there are a dozen other uses for the binoculars. If
you get a good pair the first time, you may not have to buy anymore, they last
for a lifetime.

The biggest telescope is not always the best. Most amateurs like to use the six
inch Dobsonian reflector type telescope. It is cheap, simple to use, and you can
learn a lot from it before you move on. Instead of having to play around with
controls, you will spend most of your time trying to aim and focus with this
telescope. A six to eight inch aperture is large enough to view bright images
of heavenly objects.

Smaller Telescopes

Smaller telescopes are called refracting telescopes. They have a big lens at
the front and an eyepiece in the back. Some say they are useless for astronomy,
but it is possible to do some viewing with these special telescopes.

A telescope also needs certain features in order for it to be helpful in
viewing objects. One is it must have a well-aligned and intact mirror. It must
have at least one eyepiece, two are better. The scope must have a mount that
firm and secure. Unstable mountings is a problem for beginner astronomers. You
should also have a finder that rides beside the main telescope. It makes your
field of view wider and makes it easier to find objects.

The first thing you should look for is the moon. You probably won't need to use
the finder as the moon is so big and bright. However, you may need to move the
telescope every few minutes to keep the moon in view due t the earth's
rotation. You should find many craters and brights spots where the sunlight
covers one side of the moon.

Small telescopes are great for viewing the planets. The rings of Saturn, the
phases of Venus, and the moons of Jupiter are a few of the spectacular images
you might happen across. You must use a lower power setting because higher
power makes your images dim. Usually 80-120x is good to start out.

Deep sky objects such as nebulae, galaxies, and star clusters will be faint
when compared to the planets. The brighter the deep sky object, the better you
will see it. You can certainly observe these when you find them.

Small telescope are inexpensive. You can still learn a lot about them and the
universe in the process. Take yours and see what you can find in the night sky.

Reflecting Telescopes

In 1680, Isaac Newton developed one of the first reflecting telescopes. There
was a problem wit the images having a rainbow of color surrounding them. So
instead of using a lens to focus light, Newton tried a small curved metal
mirror in the back of the telescope. He also made a discovery in 1666 about the
light of colors. Newton figured out that the scope's problems were due to the
color spectrum much more than the shape of the mirrors. He also concluded that
refraction of light couldn't be replicated without color. John Hadley developed
a telescope that used parabolic mirrors in 1722.

These types of telescopes are great for viewing comets, nebulae, star clusters,
and other galaxies. They offer a wider field of view than refracting telescopes
do. These have short focal ratios and lower magnification.

They are relatively cheap to make at home. The only problem is you have to keep
the mirrors clean and in line. If you grind the mirror wrong, it will distort
your images. Since the scopes will have a huge light focusing ability, you will
be able to view deep sky objects as well as take pictures of what you are seeing.

There are many designs that you can choose from for your telescope, but the
original Newtonian is the easiest. You will need a parabolic mirror, a
spherical mirror, and a flat mirror. The focal ratio should be around f/8 or
longer. This number refers to the brightness and width of the field of view.
For example, the ratio of f/8 is good for all around viewing.

Have fun with your creation and see what you can find in the space around you.
There are so many interesting sights to view out there and many beautiful
pictures to take.

Optical Features of Telescopes

The ability of a telescope to focus light is related to the optical features
you use. Considerations to make when purchasing optical equipment -- Aperture,
Magnification, Focal Length, Focal ratio, Wave Number, and Resolution. If you
purchase low quality merchandise, you won't be able to see what you are looking
for as well.

The most important consideration is the Aperture. This is the ability to focus
light and is related to the size of the lens or mirror that is used. In other
words, the bigger the lens or mirror, the brighter the final image. The biggest
telescope, however, is not always the best.

Magnification is dependent upon the lenses used and the distance to the
eyepiece. A general rule of thumb to follow is 40-60x per 1 inch of aperture.
Usually low magnification gives the best light.

Focal length is defined as the optical length of the telescope lens. Long focal
lengths usually mean higher magnification. Don't mistake the length of the
telescope for focal length though. Some compound telescopes light paths are
folded and become longer in a short tube.

The focal ratio tells us about he brightness and width of the field of view.
They are divided into three sections. F/10 or higher is good for viewing the
moon, planets, or stars. F/8 is great for all around viewing. F/6 and lower is
meant for viewing deep sky objects.

The wave number is also known as the wave error. It tells us how good the
mirror or lens was ground to an almost perfect surface. The smaller the number,
the better the lens or mirror. The minimum number that is acceptable is one
fourth. The performance is in the accumulation of the numbers of each optical
piece.

Resolution is the ability to find the details in the moon or a planet. It is
dependent upon how well the telescope can separate two close objects. It also
rests on the aperture and the observing conditions that are present.

Refracting Telescopes

While we have no physical evidence, we have very strong documentation that
refracting telescopes were used in England as early as the sixteenth century.
The use of telescopes became widespread in the early seventeenth century in the
Netherlands.

Hans Lippershey and Zacharias Janssen of the Netherlands claim the invention of
the original telescope. This original scope had both concave and convex lenses
so that the image would not be inverted. After the Netherlands started
producing them, they were rapidly found all over Europe.

In 1609, Galileo was visiting Venice and claims to have solved the problems
with the telescope by using a convex lens in one end and a concave in the other
end. Thus, moving the two pieces of glass further away from each other. This led
to better image viewing with less rainbow effects around the distant object.
Galileo spent much of his time to perfecting the telescope after that. His
first telescope magnified at a power of three diameters, and the best one he
made magnified at a diameter of thirty-three diameters. These last telescopes
were so great that in 1610, he discovered the satellites of Jupiter, the spots
on the sun, and the hills and valleys on the moon.

These telescopes are common today. They are made out of a long tube of metal or
wood. They have a glass lens at the front and back ends as well as an eyepiece
at the back. The tube helps to keep moisture and dust away from the lenses for
a better image. The two lenses help focus light and refract it to the back of
the tube where the eyepiece magnifies it so that you can see it clearly.

Refracting scopes have a resolution high enough to see details in binary stars
and planets. They are expensive and less useful for looking at other galaxies
or nebulae. You can see a plethora of stars and other heavenly bodies with them
though.

Creating Your Own Telescope

Materials that you will need: Magnifying glass, Masking tape, Flashlight, Thin
piece of paper, a pair of reading glass with low numbers, yardstick, and an
assistant.

* Tape the reading glasses to the yardstick making sure one lens is out on the
  side.

* Place the flashlight on a stand about twelve feet away. Shine the light at
  the lens that is sticking out.

* Place the thin sheet of paper on the side across from the flashlight. Walk
  away from the paper until you see a small picture of the flashlight on the
  paper.

* Tell your assistant take the paper to the focal point. Go around to the back
  side of the paper and check the image in your magnifying glass. Adjust until
  the image from the flashlight is enlarged.

* Take the paper away and keep looking thought the eyepiece or lens. The image
  will be brighter since the paper was removed.

* Look at other sundry items near the flashlight. Move the eyepiece or lens up
  and down or side to side to get a good image.

With a little time and effort, you can have your own telescope up and running
in a few minutes. You will see how light helps to focus the image and that
lower magnification can give you a clearer image. You also have an assistant
who can try different objects to see how clear they can be viewed and whether
the magnifying glass needs to be moved in or out. This is a simple experiment
not requiring power tools or complicated schematics. You can learn so much from
this experiment that will tell you if this is something you would like to pursue
as a hobby. Don't get frustrated that it may take a few times to get the image
right, but once you get the hang of it, there are so many neat objects out
there to view.

Finding the Telescope that Meets Your Needs

There are so many choices of telescopes out there. What do you buy and what do
you really need? Here are a few things to keep in mind so you don't buy a
telescope that won't meet what you need or want it to do.

High power magnification is not always the primary consideration. You should
have 40-60x magnification per 1 inch of aperture. The scope's ability to
enlarge an image is dependent upon the lenses used and the focal length within
the scope itself. Most objects can be seen at the lowest magnification because
there is more light being focused.

The most important feature to think about when buying a telescope is aperture.
Buy as much as you can afford. Remember, though, the biggest telescope is not
always the best one. The aperture sizes that follow are usually sufficient:
Refractors -- 3 inches or 80 mm, Reflectors -- 4 to 8 inches or 10 to 20mm, and
Compound Telescopes -- 6 to 8 inches or 16 to 20 cm.

A focuser can move the eyepiece up and down helping to adjust the focus for
each observer. There are two types of focusers -- Friction Focusers and Rack
and Pinion Focusers. Your telescope sould never shake once while you are using
these. In some telescopes, you manot get a choice.

Check out the eyepieces that come with your telescope. Some don't come with
any. Make sure you have a couple so you can vary the magnification of the
object you are viewing. You also need to be sure that the eyepiece will fit the
eyepiece holder in your telescope as not all fit all telescopes.

The type of mount you use is extremely important. Ensure it has a low center of
gravity so it doesn't tip over. It should not vibrate and it should be held in
place at a comfortable height for you.




The Best Telescopes Out There

This will be a big surprise. Can you tell me what the best telescope out there
today is? There are actually two of them. If you said your eyes, you are
correct.

You were born gifted with two telescopes that can focus from one inch to
infinity and beyond. They have a field of view of about 110 degrees, and they
have built in lens covers. They open and close at about 1/40 of a second. Eyes
can detect subtle color changes as well as any variance in color. They also
send three dimensional depth information to your brain. No telescope could ever
do all these things.

Go out before you start with the telescope and look at where you will be
pointing it. Pick out several constellations by sight and look for the moon and
a planet. Make a mental picture so you know where t go to come back to the
object when you want to. Just relax and go out in the warm night air and look
up. It really is that simple.

To get the most from learning astronomy, you must have a lot of patience. You
may go several nights without seeing anything new. This is what frustrates
beginners. Start with the moon and look at its brightness. Look for craters and
mountains. There is so much to the moon that you could find something new every
night for the next year.

Don't give up though. Even though you didn't find what you were looking for
doesn't mean it's not out there. It just means you haven't been able t see it
yet. Keep looking each night. You may find something else you weren't looking
for and that will lead to other new objects as well. Look around star clusters
and the planets. You may even spot some comets or meteors.

Factors to Consider When Purchasing a Telescope

When you go to purchase your first telescope, there are many things you should
consider before buying it. Among them are portability, Maintenance, Storage
Space, and Price. The goal is to get the most viewing ability for what you can
afford.

If you live in the city and long for some clear skies at night to view, you may
have to move the telescope to a better seeing area. Usually in the country or
rural area, you can get a beautiful expanse of sky in which to use to view your
objects. Make sure your telescope is easy to carry and will fit in your car.
Another good rule is to make sure you know how to assemble it in the dark.
Maintenance is upkeep of the telescope and its pieces. Probably the most common
maintenance will be keeping the mirrors or lenses aligned properly. Also, the
open ended telescopes are famous for collecting dust and debris. You may have
to clean the mirrors and then realign them.

When you are not using your telescope, find a safe place for it to stay. You
need a space that is dust and moisture free as possible. Cover your telescope,
when not in use, to prevent dirt and dust from getting into it.

The prices for telescopes vary these days from inexpensive to expensive and
everything in between. They can range from the $2 toy store model to a few
thousand dollars. So know what you are looking for before you buy. You may even
try a used one to see if the type is really what you want. Depending on the
type, here are some average costs for a few common telescopes: Small Reflectors
-- $250 to $1000, Achromatic Reflectors -- $250 to $1000, Large Reflectors --
$300 to $2000, Compound Telescopes -- $1000 to $3000, and Apochromatic
Refractors -- $2000 to $10,000.

Viewing Deep Sky Objects and Comets

Deep sky objects are usually located outside our solar system. The listing
includes star clusters, nebulae, galaxies, and multiple stars. There is also a
list of 110 objects on Messier's list that you can try to locate. The key to
viewing all these heavenly bodies is to go outside on a really dark night and
you must have a large telescope (one which an aperture that is greater than six
inches). Light pollution filters may also help improve your view.

What looks like one star in the sky actually becomes two or three when looking
through your telescope. There is a four part star in Orion's Nebula. There are
also stars that brighten and dim as you watch them over time. These are called
Variable Stars.

Star clusters are thousands of stars grouped together. They create a
spectacular view when looking through a small telescope. An example of this is
the Pleiades. This is a group of seven bright stars in the Taurus constellation
that can be seen with the naked eye. But once you view them through the
telescope, you will find there are thousands of stars in the cluster.

Large gas and dust clouds in space are called Nebulae. An emission nebula will
produce light where a dark nebula will absorb the light. They can be a
challenge to find.

Galaxies have massive numbers of stars that are held together by gravity and
are usually found in clusters. They come in many shapes and sizes -- spiral,
barred, elliptical, and sometimes irregular shaped. They appear as faint, fuzzy
patches of dust.

Comets are fascinating to watch as they travel across the sky. They develop
tails and can change brightness as they get closer to the sun. Not all comets
will look the same either. They may brighten or darken depending on where in
the sky you locate them.

The Hubble Telescope

Conceptualized in 1946 and launched in 1990, the Hubble telescope orbits the
Earth and sends pictures back that aren't blurred by background light or the
atmosphere. The telescope was named after Edwin Hubble who made a great
scientific breakthrough when he found that the universe was expanding. After
the Hubble was launched into space, one of the main mirrors was causing
aberrations in the pictures being sent back to Earth. In 1993, a servicing
mission was deemed necessary and they returned the telescope to its former
capabilities.

In 2007, several of the Hubble's turning gyroscopes failed, and its main camera 
stopped working. A service mission was scheduled which will hopefully allow the 
telescope to function until 2013. After that, a new  telescope will be launched 
to take its place. The James Webb Space Telescope will be superior to the 
Hubble in many ways, but will only record in infrared.

Challenges were also part of the telescope's creation. It would have to able to
withstand direct passes by the sun and behind the earth. Temperatures in these
areas were either extremely hot or extremely cold. The scientists finally came
up with a multi-layer shroud to keep the temperature within the telescope
stable at all times.

The mirrors were another problem. They were polished and grinded from the
beginning of 1979 until May of 1981. Using low expansion glass, they kept the
mirror's weight at a minimum. The mirror was finished by the end of 1981, and
they added a reflective coat of Aluminum and a protective coat of Magnesium
Fluoride.

The Hubble has given us pictures of comets, the planets, established the
presence of black holes, and other stars and galaxies nearby. To view the
wondrous images, go to http://archive.stsci.edu/hst and click on gallery. You
will find some of the most incredible pictures you have ever seen.

Telescope Mounts

Mounts for telescopes are used for several different reasons. You don't have to
hold the scope yourself while you are trying to focus on an object. It helps to
steady the scope. It frees you hands up so you can make sketches of what you
are viewing or adjust the scope for better focus.

There are two types of telescope mounts you can employ for better viewing. One
is the Alt-Azimuth. This mount is similar to a camera tripod. It uses the
vertical (altitude) axis and a horizontal (azimuth) axis to help you locate
your object. This type of telescope mount has two variations. The Ball and
Socket which has a ball shaped end that can move freely. The second type is
called a Rocker Box. This is usually made of plywood and has a low center of
gravity. It has a horizontal circular base and Teflon ball bearings for the
altitude axis. These are great mounts for a heavier telescope.

The second type of telescope mount is called the Equatorial. This mount uses
two axes that are lined up with the poles to keep track of the motion an object
takes across the sky. The axes can be Right Ascension, Polar, or Declination.
Instead of moving up and down on its axes like the Alt-Azimuth, this particular
mount is tilted toward the Earth's axis of rotation. There are two varieties of
this particular mount. One is the German Equatorial Mount. This mount is shaped
like a T. The longer axis of the T is lined up with the pole of the Earth. The
second variety is the Fork Mount. This is amount that is aligned with the
Earth's pole but is like a two-pronged fork that sits on a wedge. The prongs
are one axis and the base of the fork is the other. You can use the Equatorial
Mounts for taking pictures of the objects you find.

Looking at Globular Clusters

Globular clusters are defined as a dense grouping of thousands to millions of
stars. They are comprised of young stars at millions of years old to older
stars at billions of years old. The stars in these clusters are usually very
tightly bound together.

They are considered deep sky objects. They are easily found in the night sky in
the hours before midnight in the months of April through September. They appear
in your telescope as concentrated patches of gray mist. The amazing part is the
average distance between any of the given stars is between 1/4 to 1 1/2 light years.

The most spectacular of all is the NGC 5139. You can see it with your naked eye
because it is three times the moon's diameter. There are millions of stars that
take up your viewfinder. It is truly a wondrous site to behold. If you live in
or around North Carolina close to the latitude of +36 degrees, you will be able
to spot it easily in the night sky.

Clusters such as these are very common. In the Milky Way, there are 150 known
clusters. The Andromeda galaxy could have upwards of 500. The giant elliptical
galaxies, such as M87, have as many as 10,000. The neat thing is the globular
clusters contain some of the first stars that were created when time began.
Their origins are still unclear.

The major part of these clusters are found near the galactic core. And another
large majority lie on the celestial sky side. Clusters contain a high density
of older stars but they are not great locations for planetary systems. The
orbits of the planets become unstable in the dense clusters. These clusters can
be dated by viewing the temperature the coolest white dwarf stars are in the
group. Common results say some of these stars are 12.7 billion years old or
older.

Large Binocular Telescope

The LBT or Large Binocular Telescope is the world's most powerful optical
telescope. It will allow scientists to view planets and stars in our galaxy. It
is housed in Arizona's Mount Graham International Observatory. The telescope is
housed in a sixteen story structure, and the top ten floors of the structure
rotate.

A fifty-five ton mirror and its steel transport box were recently transported
122 miles to get to Arizona. There is the eighteen ton mirror which is made
like borosilicate honeycomb. The mirror was transported in November of 2003 to
its final home. It took three days and plenty of planning for it to arrive
unscathed.

The journey actually began when the mirror was spun cast in the giant rotating
furnace back in 1997. The team at th Mirror Lab have been creating new mirror
technologies for the past twenty years. After casting, it was polished using a
stressed-lap technique. The parabolic face of the mirror is precisely one
millionth of an inch over the entire mirror. The mechanical parts were tested
in Italy and shipped to Arizona. Partnerships all over the world helped to
bring this telescope into being. The Arizona State University, Observatories in
Milan, Padua, Rome, and Florence, Ohio State University, University of Notre
Dame, and the University of Virginia all own a part of this Large Binocular
Telescope.

The LBT's second primary mirror is 8.4 meters and polishing began soon after
the first mirror was done. Together, the two mirrors cost approximately
twenty-two million. The twin 8.4 meter mirrors are on a single telescope mount.
The images they receive are nearly ten times sharper than the Hubble. The LBT is
capable of seeing planets beyond our solar system and will allow scientists to
look deeper into the universe.

Historical Timeline for Telescopes

It seems all the technology for telescopes started back in 2560 BC. Artisans in
ancient Egypt polished rocks, glass, and semi-precious stones to make eyes for
the sarcophagi. What follows is some major points in the history of how
telescopes came to be today.

- In 470 BC, Mozi, a Chinese philosopher, focused the sun's rays by using concave
  mirrors.

- In 4 BC, Seneca the Younger used water to magnify letters and words.

- In 23, Pliny the Elder discovered doctors using a crystal ball with the sun's
  rays beaming through it to cauterize wounds.

- In the ninth century, telescopes were possibly made from Visby lenses, a Middle
  Eastern glass.

- In 1520, Leonard Digges, an English mathematician, invented two telescopes --
  Reflecting and Refracting.

- In 1608, A Dutch lensmaker, Hans Lippershey, applied for a patent on a design
  for a telescope.

- In 1609, Galileo improved on Lippershey's design and renamed it "perspicillum"
  -- An Italian word for telescope.

- In 1616, Niccolo Zucchi invented a reflecting telescope.

- In 1663, James Gregory, a Scottish mathematician, produces a telescope with a
  parabolic primary mirror and an elliptical secondary mirror.

- In 1668, Isaac Newton designed a telescope using a parabolic primary mirror and
  a flat diagonal secondary mirror.

- In 1733, Chester Moore Hall created the achromatic lens.

- In 1880, Ernst Abbe invented the first orthoscopic eyepiece.

- In 1910, The Ritchey-Chretien telescope that is used in many of the large
  astronomical telescopes is invented by George Ritchey and Henri Chretien.

- In 1930, The Schmidt camera is created by Bernhard Schmidt.

- In 1937, Grote Reber developed a telescope for wavelengths ranging from radio
  to Xrays.

- In 1944, The Maksutov telescope is designed by Dmitri Maksutov.

- In 1962, The UK launched an orbiting solar telescope.

- In 1990, the Hubble Telescope was launched into space.

- In 2013, the James Webb Space Telescope will be launched and take the place of
  the Hubble.

And this all started with the polishing of a few stones.

Galileo's Telescope

Rumors of a Dutchman creating a device that would bring objects closer so you
could see them more clearly reached Galileo in 1609. He started using the
device after he refined it to a 10-power telescope and made some amazing
discoveries with it. In 1610, he looked around Jupiter to find three satellites
all in a straight line. When he looked back, they were in all directions. He
surmised they were orbiting Jupiter and that, if this were true, then the Earth
wasn't the center of the universe. This theory went against what the church
taught.

The church believed Galileo to be quite wrong. They said everything he could
see in his new telescopic device went against everything the Bible said.
Galileo argued that even the interpreters of the Bible could have made a
mistake in the interpretation. He was accused of heresy, but proclaimed
innocent and told not to teach any of the Copernican belief system.

Unbeknowst to the church, Galileo continued to study Jupiter and the movements
of its moons. He also started working on a paper about the ocean's tides. He
was brought before the court for trying to teach the Copernican system after
being told not to. He was placed on house arrest and until his death in 1642,
he investigated even more areas of science.

He made even more fascinating discoveries with his telescope. He found there
companion stars next to Saturn which were actually the edges of the rings that
encircle the planet. He found spots on the sun's surface, and watched Venus go
through its many phases from a planet down to a sliver of light.

He published his findings in a book called "The Starry Messenger" in 1610.
People were quite excited about some of the theories found within the book.
Imagine finding for the first time that the Earth was round, and not flat. What
would you think?

Astrophotography

Astrophotography can be a rewarding pastime for some beginner astronomers.
Conventional 35mm cameras, Schmidt cameras, and CCD or Digital cameras can be
used to take your spectacular pictures.

The right pieces are needed to make this a success. You will need a shutter
cable for the 35mm, an equatorial telescope mount to help with tracking your
object for up to an hour sometimes. A "T" mount to help align the camera with
th eyepiece holder, and a guider eyepiece to help keep your object in the
center of your frame.

There are many ways to pursue this hobby. One is by using a camera mounted to
the side of the telescope. Another is have the camera on the back of the
telescope, using the scope as a guide. The last is to use a camera that is
attached to a movable mount on a tripod. If you use these, please make sure
your camera is steady and firmly attached with no vibrations or shaking.

If you are just starting out, take your digital camera and select some
constellations to snap. To set your digital camera up, check your aperture and
sensitivity settings. Also check your shutter speed. All of these should be set
to where more light can be focused especially when taking pictures at night.

Focusing means doing the manual focus on the camera or digging through the many
menus until you find the right one and set it to what you want. Then try to
shoot something far away to see if the setting you programmed works.

White balancing is usually by default. At night, the default setting will the
sky to a brown-reddish color. If you are going to incorporate long exposures of
the night sky, try setting the balance to Tungsten.

After you take several pictures, transfer them from the camera onto the
computer. Sometimes they come up grainy, try reducing the size down by
increments and you should soon have a clear picture.

Achromatic versus Apochromatic Lenses in Telescopes

In 1733, an Englishman, Chester Moore Hall, created the Achromatic refracting
lens. His design limited the color aberrations by using two pieces of glass
that were both ground and polished. These lenses usually were employed to see
red and blue light. However, the design does not block out all of the rainbow
of color around the images.

Achromatic lenses are made from a convex and a concave lens. The concave lens
is usually made out of Flint glass, and the convex from Crown glass. They form
a weak lens together and can bring two wavelengths of light into a single focus.

Apochromatic refracting lenses are made to view red, green, and blue light
wavelengths. The first ones were designed by the German physicist, Abbe. Some
type of fluorite or extra low dispersion glass is also used and the ending
result is a crisp clear image free of the rainbow of color around it. These
types of refracting lenses are more expensive than the achromatic lenses.

Apochromatic lenses require lenses that can handle three color crossings. The
are usually made from expensive fluoro-crown glass, abnormal flint glass, or
transparent liquids that are used in the space between the glass. These newer
designs allowed for the objects to be free of color around the edges, and they
produced way less aberrations than achromatic lenses.

Prices on these types of refracting lenses can run high depending on the size
aperture you need. Two to three inch apertures for Achromatic refractors can
run between $250 to $1000. Three to five inch apertures for Apochromatic
refractors can run between $2000 to $10,000. Decide which kind you will be
using before you buy one. You may just want to look at the night sky or you may
want to gaze into the next galaxy.





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