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by helterskelter20 hours ago |
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upvoteby badlibrarian20 hours ago|
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The physical version of that magic wormhole is called a slide rule.
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upvoteby eru16 hours ago|
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Another neat application, if a bit simplistic, are these mechanical paper computer that let you figure out your body-mass-index. They are basically two disks with logarithmic scales on them that you rotate relative to each other. Like a slide-rule, but circular. I think you can find them under the name 'BMI wheel'.
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upvoteby madcaptenor7 hours ago|
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These exist for various medical usages. I've seen one to compute the due date of a pregnancy (from either the date of conception or the last missed period). This was at an obstetrician's office. It was probably dropped off by a sales rep and had the logo of some medication or other.
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upvoteby all216 hours ago|
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Got a PDF? I love old books like this.
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upvoteby eager_learner20 hours ago|
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care to share the name of the said book?
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upvoteby helterskelter20 hours ago|
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Trigonometry for Navigating Officers by WP Winter

https://www.google.com/books/edition/Trigonometry_for_Naviga...

I found this book because I was a little rusty on my trig and most celestial navigation texts will just throw the PZX equation (and others) at you without breaking down what's actually being done with it on a mathematical level...it's just kind of treated like a magical black box without any discussion, and I'd rather have a complete understanding of what I'm doing and why. Having an application-specific approach also makes it a lot easier to learn.

I'm using it with Norie's Nautical Tables, which has the log tables and a whole lot else:

https://bluewaterweb.com/product/nories-nautical-tables-2025...

I'm sure there are plenty of free PDF's of log tables you can find though.

(I believe they used log tables on boats primarily because it's easier to use than a slide rule when everything is constantly rocking back and forth.)

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upvoteby dieselgate4 hours ago|
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Any other recommendations for getting into celestial navigation? I've used a sextant a few times and would like to purchase one but am aware that's only the hardware-side of things. Do the books you mentioned above provide sufficient tabulation for navigation? I sail in the Puget Sound for reference, thank you!
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upvoteby porridgeraisin8 hours ago|
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Yep, we used manual math + some log tables for calculations in our school exams as late as last decade. Since calculators were not allowed. The exam would be such that you would need the log tables once or twice over the course of the exam. Example: dividing = lookup(a)-lookup(b) and then lookup that in the inverse log (i.e exp) tables.
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