Here are two photos of my fifth astrolabe. And here’s what I’ve learned about building astrolabes. If you don’t start with the simplest one, you’ll never have the patience to build this most complex one.
The simplest one is the quadrant. It’s four parts: a straw, a string, a cardboard, and a weight. It can be built in 15 minutes and employed in 25, if you wait a little while for the glue to dry. This took more than an hour, and I didn’t realize until the end that I’d built it of the wrong materials. If I’d discovered that in the first fifteen minutes — I still would have done it all the way to the end, but it might have taken less time.
This one, I built out of foamcore. Wrong material, first of all. It cuts wrong and it’s unreliable. Heavy cardstock or light cardboard would have been better. The rete is a sheet of acetate; but again, a thin sheet of cardstock with some holes cut in it would have been a better choice. The rule and the alidade — again, heavier cardstock would have been fine. Easier to get a precise point.
On the other hand, this model is weightier than the others, befitting its more complex design. I can calculate the unequal hours of the day, also called the Chaldean hours or the Planetary Hours. I can calculate the position of the Sun if I know the date, or the position of major stars to tell the time at night, or the Mansions of the Moon, or the height of a tower or flagpole or tree.
And all this with the cruddy “first draft” of the model I made using the printouts from astrolabeproject.com. (This astrolabe, by the way, is absolutely BEAUTIFUL. The lines and traceries are elegant, the directions on how to use it are clear, and the modeling is exquisite. It’s just… difficult… to get it to come out right on foamcore. Better luck for me next time, right?
That said, there are some improvements I would like to make. I’d love to see the Mater verso and rectoproduced as an .stl file for a ShopBot to rout out. I’d love to see a rete produced the same way, that could “nest” inside the mater, and thin but rigid alidades and rules. Cardstock and cardboard may be ok in the next draft, but I’m really thinking metal or wood next time around.
My friend Daniel S. says it is critical to build your prototypes all the way to the end. Doing so has taught me a lot about materials and about cutting precision lines. I have a much better sense of how I’ll build these next time: thick cardboard mater; lighter cardboard rete, cardstock rule and alidade; sharp knife and scissors, smaller hand drill, steel ruler.
If and when I ever guide students through this process, build all five astrolabes… And build a compass and a model caravel, too. Come to think of it.