Drafting the Astrolabe: Defining the project

Allowed tools:

  • Straight-edge: NOT a ruler, I need to find a nice (straight!) length of hardwood with no markings. I may cheat and use a steel yardstick.
  • Compass: I have a nice Staedtler compass, but it will not be big enough for some of the arcs required. I may add a beam compass or experiment with cord. There may be clues in the references as to how large, shallow arcs were drawn in period.
  • Dividers: I have a nice pair of dividers that may be useful in transferring measurements.
  • Paper: 8 1/2 by 11 good quality drawing paper.
  • Eraser
  • Protractor: Cheating a bit here. I will demonstrate that I can construct a protractor before I start using a commercial one, but drawing out one by hand each time I need one seems excessive, unneeded and probably not what was done in period.
  • Astronomical tables and measurements – These would have been available to an instrument maker in period.

Technique:

  • For drawings requiring excessive geometrical construction (climate plates for example), work will be done on a working copy and transferred to a clean copy.

Sources:

  • Hartmann, Georg. Hartmann’s Practika, English translation by John Lamprey, Classical Science Press, 2002
  • Morrison, James. The Astrolabe, Janus, 2007
  • Stoeffler, Johannes. Stoeffler’s Elucidatio – The Construction and Use of the Astrolabe, English translation by Alessandro Gunella and John Lamprey, Classical Science Press, 2007

Parts:
Overall, based on astrolabes from Hartmann’s era.

  • The Front:
    • Show throne, mater and limb.
    • Limb marked in hours as the class example is.
    • Mater hollow should display traditional scale.
  • The Back:
    • Elevation scale.
    • Zodiac Ring.
    • Calendar Ring (offset).
    • Unequal Hour lines.
    • 7 and 12 shadow squares.
  • Climate plates
    • At least 5. Based on the standard set listed in Stoeffler. Adding a Pennsic Plate (40-58).
    • 5 Degree intervals on both almucantar and azimuth lines.
    • 18 degree twilight line.
    • Unequal hour lines.
    • Possibly the lunar houses if I get (more) ambitious.
  • Rete
    • Drawn properly in gothic style, pointers to major stars.
    • Zodiac ring
  • Rules and alidade
    • Drawn with proper scales.
    • Both single and double rule.
    • Alidade designed with sights.

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