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
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
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!