Download A reflecting telescope (also called a reflector curved mirrors that

A reflecting telescope (also called a reflector
reflector) is an optical telescope which uses a single or combination of
curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as
an alternative to the refracting telescope.. The reflecting telescope uses very large diameter objectives so that
more light can be collected and objects appear clearer.
Almost
ost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in
many design variations and may employ extra optical elements to improve image quali
quality
ty or place the image in a
mechanically advantageous position. Since reflecting telescopes use mirrors,, the design is sometimes referred to
as a "catoptric" telescope.
The advantages of optical telescopes like the reflecting telescope are that they are easy to purchase, easy to use,
and that the images are easy to understand. Reflecting telescopes are ideal for galaxy hunting
hunti and finding other
faint, far away objects.
All optical telescopes like the reflecting telescope have a few disadvantages. Like the refracting telescope,
colors appear in the image that are not really there. (chromatic aberration) The large diameter objectives
o
in the
reflecting telescopes minimize this problem. Additionally, optical telescopes will only detect visible light.
The Newtonian Reflecting telescope was the first
successful reflecting telescope, completed by Isaac
Newton in 1668. It usually has a curved primary mirror,
and a flat secondary mirror reflects the light to a focal
plane
lane at the side of the top of the telescope tube. It is
one of the simplest and least expensive designs for a
given size of primary, and is popular with amateur telescope makers as a home-build
build project.
A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an
image (also referred to a dioptric telescope
telescope).
). The refracting telescope design was originally used in spy glasses
and astronomical telescopes but is also used for long telephoto camera lenses.
All refracting telescopes use the same
principles. The combination of an objective lens
1 and some type of eyepiece 2 is used to gather
more light than the human eye could collect on
its own, focus it 5,, and present the viewer with a
brighter, clearer, and magnified virtual image 6.
The main disadvantage of refracting
efracting telescopes is that they are known for incorrectly bending light and
creating false colors, called a chromatic aberration. For example, a refracting telescope may put a false purple
halo around the moon. In very large telescopes that have large lenses, there is also a problem of lens sagging, a
result of gravity deforming glass.. Since a lens can only be held in place
by its edge, the center of a large lens sags due to gravity, distorting
image it produces. The largest practical lens size in a refracting
telescope is around 1 meter. Another disadvantage of refracting
telescopes is that the image can be distorted by light in the Earth’s
atmosphere. For this reason, refracting telescopes are place at the tops
This is an optical telescope image of the
Milky Way Galaxy from space. This is a side
view.
of mountains and will have large domes to shield the telescope
telesc
from
light in the atmosphere. Finally, refracting telescopes will only detect
visible light. Black holes do not give off visible light and therefore cannot be detected by optical telescopes.
Despite its limitations, it is still a good beginning tele
telescope, and it is
ideal for observing details of objects within the solar system like
craters on the moon, or details of the planets. The Griffith Observatory
in Los Angeles is an excellent example of a refracting telescope.
Griffith Observatory
A radio telescope is a form of directional radio antenna used in radio
astronomy.. The same types of antennas are also used in tracking and collecting
data from satellites and space probes. Radio telescopes will detect radio waves,
the same waves that you listen to on the radio
radio, and convert them to an image.
Radio telescopes are typically large parabolic ("dish") antennas used alone or in an array with other telescopes.
They are excellent telescopes forr viewing rath
rather
er cool objects in the universe or objects that do not give off
visible light.
Radio observatories are preferentially located far from major centers
of population to avoid electromagnetic interference (EMI) from radio,
TV, radar,, and other EMI emitting devices. This is similar to the
locating of optical telescopes to avoid light pollution,
pollution with the
difference being that radio observatories are often placed in valleys or
cones of volcanoes (like the Arecibo Radio Telescope in San Juan,
Puerto Rico) to further shield them from EMI as opposed to clear air
mountain tops for optical observatories.
VLA or Very Large Array located outside of
Socorro, New Mexico.
The main advantage of radio telescopes is that they “see” other types of light
that are not visible. They operate in the radio frequency (invisible) portion of
the electromagnetic spectrum where they can detect and collect data on radio
sources. Common radio sources include the centers of galaxies, cooler
Background Radiation of the Universe and emissions from stars. More
famously (in the
he movie Contact), this type of telescope is used by SETI to
search for extraterrestrial life. You can help them in their search by going to
http://setiathome.berkeley.edu/ .
The main disadvantages to radio telescopes
elescopes are that they are expensive
because you must have many of them is an isolated location. Scientists must
Images of Galaxy M87 from Radio
Telescope Arrays
A
VLA and VBLA
have extensive training on how to use the arrays as well as to understand the images.
A space observatory is any instrument in outer space which is used for
observation of distant planets, galaxies, and other outer space objects. This
category is distinct from other observatories located in space that are
pointe
pointed
d toward the earth for the purpose of scientific research,
research spying or
weather forecasting
forecasting.
Many space observatories have already completed their missions, while
others continue operating, and still others are planned for the future. Space
observatories are important because they can not only make observations in
the visible range, like the Hubbl
Hubblee Space Telescope, but they allow us to see
light outside of visible range
range, such as x-rays.. One great example would be
the SOHO, the Solar and Heliospheric Observatory,, which allows us to
study the Sun
un in Ultraviolet, Radio and X Rays.
These types of observatories
es are especially important because the
atmosphere blocks some types of light from hitting the surface of the
Earth, which keeps us from studying that light
light. For example, X-ray
astronomy is nearly impossible when done from the Earth, and has
reached its current importance in astronomy only due to orbiting X
X-ray
telescopes such as the Chandra
handra observatory and the XMM-Newton
observatory. Infrared and ultraviolet light waves are also greatly blocked
by our atmosphere, and we must go to space to study these types of light
from stars.
X-ray
ray image of Casseopeia II Constellation
of Stars from Space Observatory Chandra
The main disadvantages of space observatories are that they are expensive. Space observatories must be
launched
unched into space and require many years of training to use. If something goes wrong with the telescope, the
problem must be detected on Earth, a team of astronauts must be trained on how to fix the problem, and then the
crew must be launched into space. X-ray
ray and UV light images can be very difficult to understand.