Friday, February 10, 2012

Build an astrolabe


This paper presents a hands-on introduction to the medieval astrolabe, based around a working model which can be constructed frophotocopies of the supplied figures. As well as describing how to assemble the model, I also provide a brief explanation of how each of its various parts might be used. The printed version of this paper includes only the parts needed to build a single model prepared for use at latitudes around 52◦N, but an accompanying electronic file archive includes equivalent images which can be used to build models prepared for use at any other latitude. The vector graphics scripts used to generate the models are also available for download, allowing customised astrolabes to be made.

"Building a Model Astrolabe" by Dominic Ford

Or, try this simple method...

What You'll Need:

Plastic protractor
Weight (washer, rock, or fishing weight)
Pen and paper

Step 1: Tie a 12-inch piece of string to the hole in the middle of the crossbar on the protractor. Tie a weight to the other end.

Step 2: Hold the protractor so that the curved part is down and the zero degree mark is closest to you.

Step 3: Sit on the ground, and look along the flat edge of the protractor with your eye at the zero mark. Point the flat edge at the star whose position you want to measure.

Step 4: Once you have the star at the end of your sight, hold the string against the side of the protractor.

Step 5: Note which degree mark the string crosses. Write this down in your notebook. This number tells you how many degrees above the horizon your star is.

Step 6: Take readings for several stars.

Step 7: Return every 30 minutes, and take new readings. Notice the pattern in which the stars seem to move across the sky as the earth turns.

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