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Here's a modern analog machine for "calculating" the Sun's Declination. It's strictly an educational demo, and kids love turning "cranks" like this one has, so I imagine it has some merit. This device could serve as the basis for a "real" analog Dec computer. As I see it, it's missing one "gear" to pick up the eccentricity of the Earth's orbit. Or would that require more than one gear?? Would it work otherwise? :)

The machine is at the South Australian Maritime Museum in Adelaide. Has anyone been there? I also found a few navigational instruments, and there are demos and discussions of Matthew Flinders (no surprise there!). It seems to be quite a nice museum, but I notice it's not particularly close to the water.

I ended up exploring this museum's online images by passing through a deep, antipodal rabbithole. I'm planning a Modern Celestial workshop for this weekend, and I noticed that the subSun point at the beginning of the Saturday session, when I talk about this special Sun-at-zenith location, is about 8° North and smack in the middle of the Atlantic. That reminded me of the view from the shore here in southern New England... If I face southeast, I'm looking across the Atlantic, more or less directly towards Saturday's subSun point. And if I travel in that direction and keep right on going, straight as possible (great circle, in other words), I pass between Africa and South America, emerge into the southern Indian Ocean and eventually hit land in southern Australia. When I traced the route this time, I ended up quite close to Adelaide and thought, "what's in Adelaide?" --a thought which I do not believe I had ever had before :). I then discovered their maritime museum in Google Maps and noticed that there's a vast online collection of visitor images. Fun to explore, and that's where I found this analog Declination "computer".

Frank Reed

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