An ancient astronomical instrument used in navigation - More complex ones also had mathematical functions.
I'm interested in making precision devices with my makerbot and this seemed like a good place to start - This is version 1, if it prints OK then I will progress with other versions with more features (such as a circular slide rule)
I'm posting the sketchup files in case anyone would like to modify, or improve the design (I'm new to 3d modeling so it's pretty crude)
This model is untested.
Warping may be an issue with such a large flat object.
2 STLs, 1 for the main disk, and 1 for the center peg and the observing arm.