Section Introduction Page

Radio vs. Optical Astronomy

Radio astronomy studies astronomical objects at radio frequencies, rather than the optical frequencies associated with the common viewing telescope. The initial detection of radio waves from an astronomical object was made in the 1930s, so that much of radio astronomy is fairly new and offers many research opportunities.  Both radio and optical frequencies are part of the wider electromagnetic spectrum of radiation.  Other parts of the electromagnetic spectrum for astronomical objects are not necessarily observed from Earth because of atmospheric absorption.  These other wavelengths can be studied from space-based telescopes.  Like optical objects, radio-emitting sources exist in great variety: planets, stars, galaxies, as well as the cosmic microwave background radiation.  Radio astronomy is conducted using large radio antennas referred to as radio telescopes.  The SARA sections tabs on this page helps organize the different types of radio objects and how to observe them.  A radio telescope has three basic parts: the antenna, the receiver, and the output display.  There are many types of radio telescopes depending on the part of the radio frequency spectrum (band) being observed.  The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI).  It is defined as one cycle per second.

Radio Astronomy Bands and Detection

Information on radio frequency bands is commonly found on the Internet.  A few links below are noted from the United Kingdom Amateur Radio Astronomy Network (UKARA); Wikipedia, and NASA.  As you explore the SARA site, notice the frequency of observation for particular phenomena or astronomical objects and where it is positioned in the radio frequency bands.

http://www.ukaranet.org.uk/basics/frequency_allocation.htm

http://en.wikipedia.org/wiki/Electromagnetic_spectrum

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://www.radio-astronomy.org/pdf/sara-beginner-booklet.pdf

http://en.wikipedia.org/wiki/Radio_spectrum

Radio wavelengths are much longer than those of optical light.  This property of photons affects the way one would detect them.  Apart from human eye visual detection, other optical detectors such as charge coupled devices (CCDs) detect the individual light photons that strike the detector surface, and the response is proportional to the number of photons striking the surface, and hence is a measure of the intensity of the source that is generating the photons.  However, such detectors will not work on radio photons. The energy carried by these radio photons is too low to cause a reaction in a detector.  Therefore, in radio astronomy other detection techniques are used: a receiver instead detects the wave nature of the radio wave rather than the photon nature. Information about the phase and amplitude of the wave is gathered.

Beginner's Tab

Information for beginners can be found in here.

 

The Six SARA Sections

The tabs below will link to six different SARA sections.  Depending on your interests, you may want to narrow your interest within SARA and join a section by contacting the section coordinator.  Each section is under continual development and grows by the efforts of its members.  Many volunteer leadership roles are available: section coordinators, sub-section coordinators, assistant coordinators, etc.  Each section will provide basic information, context, references and links to SARA projects in the field of research.  Other links under development include connecting the sections to an index of SARA listserv archive topics and the SARA Journal table of contents for back issues.  

Solar System/ Stellar/ Galactic & Cosmology/ Electronics & Instrumentation/ Analytic/ Outreach

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SARA is dedicated to the exploration of radio astronomy at the amateur level. Many amateurs are engaged in developing hardware, software, and methodologies to expand the limits of amateur radio observation. Such amateurs impose intriguing opportunities. With peer review, they can develop new approaches to radio astronomy observation, or offer an equally valuable dissertation on explanations to misidentified radio observations and their nature.  SARA welcomes positive diversity of opinion but does not necessarily embrace those opinions as it own.