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Basics of Astronomy
Astronomy is the study of the all the objects beyond our world, such as the stars, comets, stars clusters, and other planets. In order to practice astronomy, you need to be able to recognize those objects in the outer sky. There is one easy technique to begin practicing astronomy. And you don´t need any expensive equipment! but your eyes and hands. Learn the basics and begin your experience through the night sky.
First, you have to know that distances in the outer sky are extremely vast and that the distances from one celestial object to another are not easily measured with standard units of distance (kilometers, miles, etc.) used on earth. Second, astronomers measure distances in the sky, using angular measures.
Knowing these basic facts will help you going from star to star in the sky, so choose a clear night, and start recognizing some of the celestial objects above in the sky!
When you look at the sky at night, one of the most recognizable objects is the moon; now extend your arm, and point at the moon with your thumb finger. You will notice that 1/4 of your finger covers entirely the moon.
The tip of your thumb finger hold at arm´s length is about 2°. The moon measures ½°. The angular measure from the horizon to the point above your head (the zenith) is 90°. It would require 180 moons to be lined up to cover that distance. Your fist held at arm´s length would cover 20 moons (10°).
Orion, one of the most noticeable constellations in the sky can be seen from any place on earth; it is noticeable throughout all the winter season in the northern hemisphere. It can be seen appearing in the eastern horizon every day after dark, from November to February, reaching its highest height (the zenith) by mid January: being the three white stars (alnitak, Alnilam, and Mintaka) in the middle (Orion´s belt) one of the most stand out features. A little bit below the belt is the Orion nebula (M42).
Drawing an imaginary line from Orion´s belt towards the northwest direction will lead to Aldebaran: (the eye of the Taurus) in the constellation of Taurus. The stars Rigel y Betelgeuse point to castor and Pollux, in Gemini. A line from bellatrix to Betelgeuse point to Procyon in Canis Minor, one line from Orion’s belt pointing downwards will lead to Sirius, in Canis Major.
Understanding How to Navigate Through the Night Sky
Another group of stars that are visible with the unaided eye (the Pleiades), are located just high above Aldebaran by the width of two fists (20°) held at arm´s length. An example of how a single constellation can help us navigate through the night sky.
As can be seen, astronomy is not so difficult to practice, and there is no need of any equipment at all, but your unaided eye and a little understanding at how to find your way in the sky. With a little practice and determination, day by day, anyone can become a good astronomer!