what is the role of the amateurs in it?
The Astronomical Society of the Pacific is one of such clubs that meet on a regular basis and often host star parties.
Astronomer
 The Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. 
who designates the stars? Astronomers who are they? They are scientists in the field of astronomy who focus their studies on a specific question or field outside the scope of Earth. which ancient civilizations studied the above mentioned field? UNANSWERABLE
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Astronomer [SEP] Amateur astronomers
While there is a relatively low number of professional astronomers, the field is popular among amateurs. Most cities have amateur astronomy clubs that meet on a regular basis and often host star parties. The Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. Like any hobby, most people who think of themselves as amateur astronomers may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to the very ambitious, who own science-grade telescopes and instruments with which they are able to make their own discoveries and assist professional astronomers in research.