Guest Contributor

My cabin had been in disrepair for a few years , so I eventually started making a few repairs by myself . Bad idea , but it did keep me busy for many weekends , so when I finally resolved to sell it instead of trying to fix it , I ended up with idle hands . I needed something to keep my hands occupied . On something smaller , preferably . This is how I decided , in January 2015 , to build a planispheric brass astrolabe . The astrolabe used to be a pivotal instrument on the desk of all astronomers from its invention around 2,000 years ago until around 1600 … but before I tell you why such was the case , I need to tell you what an astrolabe is and what it ’ s used for . Most people interested in astronomy have heard of

Greek astronomers such as

The author ’ s completed brass astrolabe

COURTESY OR PIERRE PAQUETTE

Hipparchus and Ptolemy . Few , though , have heard about the instruments our forebears were using . One of them , the armillary sphere , consists of a set of rings around a central ball or sphere representing the Earth . It was invented independently in China and in Greece around the third to the first centuries before the Common Era ( BCE ). Three parallel rings represent the equator and the tropics ( those two being smaller than the equator ), with a fourth representing the ecliptic , inclined and touching the top ( or Cancer ) tropic on one side and the bottom ( or Capricorn ) tropic on the other side . A fifth ring is perpendicular to the equator and tropics and represents the meridian . It ’ s a beautiful

instrument in and by itself , and I was always amazed when I would see the Meritas Trophy , an armillary sphere made by Québec ( Canada ) amateur astronomer Réal Manseau in the 1970s , which won a few prizes at Stellafane convention in Vermont ( USA ) and is offered yearly by the Québec Amateur Astronomers Federation to one of its members who participated in outreach programs and such . Legend says that Greek astronomer Ptolemy was riding his camel or horse one day , and that his armillary sphere fell off and was trampled upon by the animal . Upon picking it up , he supposedly realized it could still be used , and that he came up with the astrolabe from what remained . While this story is most likely not true , the planispheric astrolabe