Following Kepler

I’ve been rather quiet on this blog lately. A good deal of that has been due to working on videos for my YouTube channel. However, I haven’t posted a video there for nearly a month. So what have I been working on?

There’s been a few big projects, but the one I’d like to introduce now has to do with the Astronomicum Caesareum by Peter Apian. For those that aren’t familiar, this book was published in $1540$ and uses volvelles (rotating paper discs) to physically represent the Ptolemaic model. This, along with some tables, allows users to physically manipulate these analog calculators to determine the positions of planets, eclipses, and more. And it doesn’t hurt that the book is stunning. I got to see a copy when I visited the Adler Planetarium as part of the 16th Biennial History of Astronomy Workshop.

Although I haven’t mentioned it previously, this is a book that I’ve been interested in for quite some time now. Indeed, I’ve quietly been working on a translation¹ as I’d hoped to take some of the good scans of the various extant copies² and reconstruct the volvelles based on how Apian says they’re supposed to work.

But, while at the workshop I mentioned above, I was reminded that there is a facsimile version of the work. It’s expensive, but I keep my eye out and found one for a pretty substantial discount on what they normally sell for. So, I scooped one up and, as I’ve been translating, I’ve been matching my translation to the facsimile to make sure things line up.

However, there’s been a bit of an issue: Things aren’t lining up. And it’s the facsimile that’s the problem.

So, I’m setting about trying to fix my copy. So, to that end, I’ll be doing a series of posts documenting the issues I’ve found, diving into the extant copies, and showing what I’ve done to fix it. Below the fold, I’ll keep an index of posts for anyone that wants to know what needs to be done to get one of these copies in working order. Continue reading “Astronomicum Caesareum Facsimile Restoration Project – Overview”