Drafting the Astrolabe 12: Planning the climates

Before I tackle the next bit I need to plan out what I want to do. I want a set of five climate plates, one for each of five different latitudes. One of these will need to be for the latitude of Cooper’s Lake, the site of the annual Pennsic War. Another should be the latitude of my home, of course. For the other three I will select from latitudes of Major cities I have visited.
This gives me the following list:
  • 39 degrees – My home latitude
  • 41 degrees – Pennsic War
  • 49 degrees – Paris
  • 52 degrees – London/Cambridge
  • 56 degrees – Copenhagen
As for drawing the plates themselves, it occurs to me that a lot of the work is going to be either identical or very similar for each plate. This suggests to me that doing all five plates at once, that is, completing each step on all five plates before moving on, will be the most efficient way forward.
The process for creating a climate plate breaks down as follows:
  1. Draw the outer edge of the plate. Add the Meridian and east-west line. Draw the Tropics and Equator.
  2. Draw the almucantars (circles of elevation) to include the horizon and the twilight line.
  3. Draw the azimuth arcs
  4. Draw the equal hour arcs
As I did with the front and back of the astrolabe I will detail each step as I go along.
Watch this space!

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