|
Table of Contents
Amateur
astronomy,
also called backyard astronomy, is a
hobby whose participants enjoy watching the
night sky (and the day sky too, for sunspots,
eclipses, etc.), and the plethora of objects
found in it, mainly with portable telescopes and
binoculars. Even though scientific research is
not their main goal, many amateur astronomers
make a contribution to astronomy by monitoring
variable stars, tracking asteroids and
discovering transient objects, such as comets.
Such efforts are one of the relatively few ways
interested amateurs can still make useful
contributions to scientific knowledge.
Overview
The typical
amateur astronomer is one who does not depend on
the field of astronomy as a primary source of
income or support, and does not have a
professional degree or advanced academic
training in the subject. Many amateurs are
beginners, while others have a high degree of
experience in astronomy and often assist and
work alongside professional astronomers.
Amateur
astronomy is usually associated with viewing the
night sky when most celestial objects and events
are visible, but sometimes amateur astronomers
also operate during the day for events such as
sunspots and solar eclipses. Amateur astronomers
often look at the sky using nothing more than
their eyes, but common tools for amateur
astronomy include portable telescopes and
binoculars.
People have
studied the sky throughout history in an amateur
framework, without any formal method of funding.
It is only within about the past century,
however, that amateur astronomy has become an
activity clearly distinguished from professional
astronomy, and other related activities.
Amateur
astronomy objectives
Collectively,
amateur astronomers observe a variety of
celestial objects and phenomena. Common targets
of amateur astronomers include the Moon,
planets, stars, comets, meteor showers, and a
variety of deep sky objects such as star
clusters, galaxies, and nebulae. Many amateurs
like to specialize in observing particular
objects, types of objects, or types of events
which interest them. One branch of amateur
astronomy, amateur astrophotography, involves
the taking of photos of the night sky.
Astrophotography has become more popular for
amateurs in recent times, as relatively
sophisticated equipment, such as high quality
CCD cameras, has become more affordable.
Most amateurs
work at visible wavelengths, but a small
minority experiment with wavelengths outside the
visible spectrum. The pioneer of amateur radio
astronomy was Karl Jansky who started observing
the sky at radio wavelengths in the 1930s, and
interest has increased over time. Non-visual
amateur astronomy includes the use of infrared
filters on conventional telescopes, and also the
use of radio telescopes. Some amateur
astronomers use home-made radio telescopes,
while others use radio telescopes that were
originally built for astronomy research but have
since been made available for use by amateurs.
The One-Mile Telescope is one such example.
Common tools
Amateur
astronomers use a range of instruments to study
the sky, depending on a combination of their
interests and resources. Methods include simply
looking at the night sky with the naked eye,
using binoculars, and using a variety of optical
telescopes of varying power and quality, as well
as additional sophisticated equipment, such as
cameras, to study light from the sky in both the
visual and non-visual parts of the spectrum.
Commercial telescopes are available new and
used, but in some places it is also common for
amateur astronomers to build (or commission the
building of) their own custom telescope. Some
people even focus on amateur telescope making as
their primary interest within the hobby of
amateur astronomy.
Although
specialized and experienced amateur astronomers
tend to acquire more specialized and more
powerful equipment over time, relatively simple
equipment is often preferred for certain tasks.
Binoculars, for instance, although generally of
lower power than the majority of telescopes,
also tend to provide a wider field of view,
which is preferable for looking at some objects
in the night sky.
Amateur
astronomers also use star charts that, depending
on experience and intentions, may range from
simple planispheres through to detailed charts
of very specific areas of the night sky. A range
of astronomy software is available and used by
amateur astronomers, including software that
generates maps of the sky, software to assist
with astrophotography, observation scheduling
software, and software to perform various
calculations pertaining to astronomical
phenomena.
Amateur
astronomers often like to keep records of their
observations, which usually takes the form of an
observing log. Observing logs typically record
details about which objects were observed and
when, as well as describing the details that
were seen. Sketching is sometimes used within
logs, and photographic records of observations
have also been used in recent times.
The Internet is
an essential tool of amateur astronomers. Almost
all astronomy clubs, even those with very few
members, have a web site. The popularity of CCD
imaging among amateurs has lead to large numbers
of web sites being written by individuals about
their images and equipment. Much of the social
interaction of amateur astronomy occurs on
mailing lists or discussion groups. Discussion
group servers host numerous astronomy lists. A
great deal of the commerce of amateur astronomy,
the buying and selling of equipment, occurs
online. Many amateurs use online tools to plan
their nightly observing sessions using tools
such as the Clear Sky Chart.
Common
techniques
While a number
of interesting celestial objects are readily
identified by the naked eye, sometimes with the
aid of a star chart, many others are so faint or
inconspicuous that technical means are necessary
to locate them. Many methods are used in amateur
astronomy, but most are variations of a few
specific techniques.
Star hopping
Star hopping is
a method often used by amateur astronomers with
low-tech equipment such as binoculars or a
manually driven telescope. It involves the use
of maps (or memory) to locate known landmark
stars, and "hopping" between them, often with
the aid of a finderscope. Because of its
simplicity, star hopping is a very common method
for finding objects that are close to naked-eye
stars.
More advanced
methods of locating objects in the sky include
telescope mounts with setting circles,
which assist with pointing telescopes to
positions in the sky that are known to contain
objects of interest, and GOTO telescopes,
which are fully automated telescopes that are
capable of locating objects on demand (having
first been calibrated).
Setting
circles
Setting circles
are angular measurement scales that can be
placed on the two main rotation axes of some
telescopes. Since the widespread adoption of
digital setting circles, any classical engraved
setting circle is now specifically identified as
an "analog setting circle" (ASC). By knowing the
coordinates of an object (usually given in
equatorial coordinates), the telescope user can
use the setting circle to align the telescope in
the appropriate direction before looking through
its eyepiece. A computerized setting circle is
called a "digital setting circle" (DSC).
Although digital setting circles can be used to
display a telescope's RA and Dec coordinates,
they are not simply a digital read-out of what
can be seen on the telescope's analog setting
circles. As with go-to telescopes, digital
setting circle computers (commercial names
include Argo Navis, Sky Commander, and NGC Max)
contain databases of tens of thousands of
celestial objects and projections of planet
positions.
To find an
object, such as globular cluster NGC 6712, one
does not need to look up the RA and Dec
coordinates in a book, and then move the
telescope to those numerical readings. Rather,
the object is chosen from the database and arrow
markers appear in the display which indicate the
direction to move the telescope. The telescope
is moved until the distance value reaches zero.
When both the RA and Dec axes are thus "zeroed
out", the object should be in the eyepiece. The
user therefore does not have to go back and
forth from some other database (such as a book
or laptop) to match the desired object's listed
coordinates to the coordinates on the telescope.
However, many DSCs, and also go-to systems, can
work in conjunction with laptop sky programs.
Computerized
systems provide the further advantage of
computing coordinate precession. Traditional
printed sources are subtitled by the epoch
year, which refers to the positions of celestial
objects at a given time to the nearest year
(e.g., J2005, J2007). Most such printed sources
have been updated for intervals of only about
every fifty years (e.g., J1900, J1950,
J2000).
Computerized sources, on the other hand, are
able to calculate the right ascension and
declination of the "epoch of date" to the exact
instant of observation.
Telescopes
Most amateur
astronomers will choose from the three most
common types of entry-level telescopes; the
refractor, the reflector, and the catadioptric.
Refractor
telescopes
Refractor
telescopes are a type of
optical telescope that uses a
lens as its
objective to form an image (also
referred to a
dioptric
telescope). The refracting telescope
design was originally used in spy glasses and
astronomical telescopes but is also
used for long
telephoto camera
lenses. It is the earliest type of telescope,
and although they are still available today and
are an economical choice, they are often low
power and are larger than other types of
telescopes. Most amateur astronomers are
looking for more power in a smaller telescope.
Reflector telescopes
A reflecting telescope (also called a 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 which, at that
time, was a design that suffered from severe
chromatic aberration. Although
reflecting telescopes produce other types of
optical aberrations, it is a design that allows
for very large diameter
objectives. Almost 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 quality or place the image in a
mechanically advantageous position. There are
many different types of reflector telescopes,
including Newtonian ( a simple design popular
with home telescope builders) and the Cassegrain
(compact but less powerful).
Catadioptric telescopes
The catadioptric telescope is actually a type of
reflector telescope, but which combine
specifically shaped mirrors and lenses in
designs that have all spherical surfaces that
are easier to manufacture, have an overall
greater degree of error correction than their
all lens or mirror counterparts, have a wide
field of view, take advantage of a
folded optical path, or a combination of any or
all of these attributes. Many types employ
“correctors”, a lens or curved mirror in a
combined
image-forming optical system so that
the reflective or refractive element can correct
the aberrations produced by its counterpart, the
basic reflector telescope.
‘Schmidt-Cassegrain’
telescopes are one of the most
popular commercial designs on the
amateur astronomical market, having
been mass-produced since the 1960’s. The design
replaces the Schmidt Camera film holder with a
Cassegrain secondary mirror making a folded
optical path with a long focal length and a
narrow field of view. This makes for a compact
telescope with the clarity of a refractor
telescope but the power of a Newtonian
reflector.
“GoTo”
Telescopes
GOTO telescopes
have become more popular since the 1980s as
technology has improved and prices have been
reduced. With these computer-driven telescopes,
the user typically enters the name of the item
of interest and the mechanics of the telescope
point the telescope towards that item
automatically. They have several notable
advantages for amateur astronomers intent on
research. For example, GOTO telescopes tend to
be faster for locating items of interest than
star hopping, allowing more time for studying of
the object. GOTO also allows manufacturers to
add equatorial tracking to mechanically simpler
alt-azimuth telescope mounts, allowing them to
produce an overall less expensive product.
Scientific
research
Scientific
research is most often not the main goal
for many amateur astronomers, unlike
professional astronomy. Work of scientific merit
is possible, however, and many amateurs
successfully contribute to the knowledge base of
professional astronomers. Astronomy is sometimes
promoted as one of the few remaining sciences
for which amateurs can still contribute useful
data. To recognize this, the Astronomical
Society of the Pacific annually gives Amateur
Achievement Awards for significant contributions
to astronomy by amateurs.
The majority of
scientific contributions by amateur astronomers
are in the area of data collection. In
particular, this applies where large numbers of
amateur astronomers with small telescopes are
more effective than the relatively small number
of large telescopes that are available to
professional astronomers. Several organizations,
such as the Center for Backyard Astrophysics,
exist to help coordinate these contributions.
Amateur
astronomers often contribute toward activities
such as monitoring the changes in brightness of
variable stars, helping to track asteroids, and
observing occultations to determine both the
shape of asteroids and the shape of the terrain
on the apparent edge of the Moon as seen from
Earth. With more advanced equipment, but still
cheap in comparison to professional setups,
amateur astronomers can measure the light
spectrum emitted from astronomical objects,
which can yield high-quality scientific data if
the measurements are performed with due care. A
relatively recent role for amateur astronomers
is searching for overlooked phenomena (e.g.,
Kreutz Sungrazers) in the vast libraries of
digital images and other data captured by Earth
and space based observatories, much of which is
available over the Internet.
In the past and
present, amateur astronomers have played a major
role in discovering new comets. Recently
however, funding of projects such as the Lincoln
Near-Earth Asteroid Research and Near Earth
Asteroid Tracking projects has meant that
most comets are now discovered by automated
systems, long before it is possible for amateurs
to see them.
Societies
There is a large
number of amateur astronomical societies around
the world that serve as a meeting point for
those interested in amateur astronomy, whether
they be people who are actively interested in
observing or "armchair astronomers" who may be
simply interested in the topic. Societies range
widely in their goals, depending on a variety of
factors such as geographic spread, local
circumstances, size, and membership. For
instance, a local society in the middle of a
large city may have regular meetings with
speakers, focusing less on observing the night
sky if the membership is less able to observe
due to factors such as light pollution.
It is common for
local societies to hold regular meetings, which
may include activities such as star parties or
presentations. Societies are also a meeting
point for people with particular interests, such
as amateur telescope making.
Wikipedia Links to amateur
astronomy organizations:
|
Astronomy
is a hobby that has been practiced for
thousands of years and has evolved over the
years. Learning about the planets and
constellations are intriguing facts that
astound us since we are children. Getting
started is very easy as all it takes is a
view of the sky. More advanced users get
some of the affordable and terrific
equipment available.