Radio Telescope
It was Einstein who made the real trouble. He announced in
1905 that there was no such thing as absolute rest. After that there
never was.
--
Steven Leacock
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for a live view! - [R-MC network only])
A Radio Telescope is a device… no
that would be a boring intro.
When you think of Astronomy, what do you see, perhaps
the rings of Saturn, the cloud bands of Jupiter, or the Sun with
flares blazing outward into space? Or, maybe you imagine distant
galaxies, black holes, or quasars. In any case, radio astronomy
is as much a part of observing these phenomena as optical astronomy.
The difference between the two is how one looks at the objects.
Most optical telescopes reflect or refract the light so that astronomers
could, in principle, actually see the objects that they are observing.
The Hubble Space Telescope (HST) produces images that are then downloaded
and seen here on earth. Simply stated, optical telescopes gather
light, focus it, and a picture or image is produced, or the light
may be analyzed with other instruments such as photometers or spectrometers.
Radio telescopes are very similar in that they also
gather light, amplify it, and then display an image. However, the
greatest difference is the telescope itself. The difference is simply
the wavelengths of light being observed. Optical astronomy observes
light from about 400 to 700 nm, whereas radio astronomy observes
from 1cm to decameter wavelengths. These are just two different
sections of the electromagnetic (EM) spectrum. The EM spectrum may
be categorized, from shortest to longest wavelengths, as gamma rays,
x-rays, ultraviolet, optical, infrared, microwaves, and radio. All
light and radiation are can be specified as due to one of these
sources. Indeed, they are all the same basic phenomenon, differing
only in the source of the radiation.
A radio telescope can be designed in several ways,
ranging from simple dipoles to 100-meter parabolic antennas. Most
small radio telescopes are made of the typical mesh parabolic dish.
The mesh allows wind, rain, and sunlight to pass through, yet at
the same time reflects and focuses the larger radio waves. Optical
telescopes need to be manufactured very accurately because any small
imperfections would divert the small 400-700 nm waves. Recall the
HST problem. When launched, the primary mirror suffered from a form
of spherical aberration. The mirror actually had an improper shape!
They had to install corrective optics to accommodate the telescope's
wrongly figured mirror. These problems may affect radio telescopes
also. Dents made by hail or other deformations caused by gravity
are common problems. To help with slight changes in the surface
due to weather and gravity, the new Green Bank Telescope has hydraulics
that adjust panels on its surface. Some new optical telescopes,
for example the Keck telescopes at Mauna Kea, also use these techniques,
called adaptive optics.
The
primary goal of the project has been to construct and bring to First
Light a radio telescope. (First light is the term used by astronomers
when a telescope makes its first observation.) Last year the project
began by researching the fundamentals of radio astronomy and methods
of constructing radio telescopes. By the beginning of this year
we had acquired most of the necessary equipment, and the antenna
was installed this spring. The next step, achieved this summer,
was to bring together and install the components of the system.
On 2001July 13 we reached first light, observing the Sun. The following
weekend, the galactic plane was also observed in a transit scan.
The goal was accomplished through ingenuity
and perseverance, because many things did not go as planned. However,
the problems were expected in a project such as this. Each hurdle
was a learning experience for us, and therefore a lesson that can
be taught to the next person who endeavors to construct a radio
telescope. The future plans section documents what we plan to accomplish
in the next year, but no matter what we do, we will make many observations
and scans of the sky at 21 cm and ultimately see things in a way
not often imagined!
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