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Writer's pictureValentina

The Celestial Compass that Navigated Astronomy's Course

Updated: Aug 12

Dear young scientist,


My name is Juna Asfuroglu, and in today's blog, I will be introducing to you the celestial compass. The astrolabe is an ancient navigational and astronomical instrument that was used to measure the altitude of celestial bodies, such as the sun and stars, above the horizon. The astrolabe was a very old instrument invented by Apollonius of Perga during the 2nd century BCE in ancient Greece. 


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Apollonius of Perga was an ancient Greek mathematician and engineer who lived in the 3rd century BCE. He made various contributions in the field of astronomy and mathematics, one of those inventions was a portable device called the astrolabe. The astrolabe revolutionized the techniques and strategies used to make discoveries in astronomy. 


Not only did it make accurate calculations of the positions of celestial objects, but made it an essential device for calculating the magnitude of stars. In one of the books of AL-sufi “The Book of fixed stars,” he drew patterns of stars that portrayed people, because of their pattern, this is what we know as constellations. 

Astronomy

He categorized the stars into 48 classical Greek constellations, as well as several additional southern constellations. He used an astrolabe to help him carefully make accurate measurements of each star's position and then compared their position in the night sky over the years to note their changes. 


So how was the astrolabe built? The structure of the astrolabe was carefully assembled and measured so that it aligns accurately with the celestial objects; it consists of a circular base plate called the mater, which was carefully shaped and engraved with graduated scales and annotations. 


Atop the mater sat a movable pierced plate called the rete, which represented the positions of stars. A sighting alidade with two vanes was attached to the back, allowing the user to align the instrument with celestial objects. Interchangeable tympan plates engraved for different geographic latitudes could also be fitted inside the mater. 


Not only did the astrolabe contribute to making tons of discoveries it also helped astronomers determine the time of day, and was used by sailors to help them sail across the sea. Using the astrolabe you can find out the current season and the geographical latitude of celestial objects. It also enabled mathematicians to use this numerical data to make the necessary calculations and predictions. 


Many of you reading this article are probably interested in astronomy, and wondering how you can get such an instrument. Well, fear not I have found an excellent alternative that you can even make at home! This video will provide you with step-by-step instructions on how to build a simple and effective astrolabe. You can use it to measure the apparent magnitude of celestial objects and keep track of their movements. This practice I believe will reflect your passion for astronomy, and make you appreciate its wonders while being able to do simple astronomical calculations.


A tutorial on how to make a homemade astrolabe:


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