(no subject)

[stellar_muddle]

So after a day spent looking at Da Vinci Machines, rushing around the local museum and avoiding the heat (a high round 41 degrees C... and down to 33 degrees now), this seems somewhat appropriate. Anyone know how to use it? We played a little with sextants in first year astro labs, but they had put a few extra bits on by then. I am fairly certain it wasn't used as a pocket calculator though and I wouldn't class it as ancient...

And for those who are fans, Andy Irvine is currently in NZ touring. Good music and from the half a concert Z and I caught several years back in Chch round Valentine's Day, a good live show. Missed him in Aussie this round, but he only hit Melbourne and Sydney region anyway, so wouldn't have helped to know.

Comments

[vonstrassburg.livejournal.com]

It's not a true logarithm, because it isn't built on a linear logarithmic scale and can't produce arbitrary products. It is based on a "golden rectangle" algorithm which can be used to produce products and factors of sines and cosines of particular angles, which is all that is needed in this case. It is, however, essentially logarithmic in scale for those sines and cosines -- hence "logarithmic protractor" not "slide rule". Check the curve on the photo if you want to do the maths yourself.

Golden rectangle algorithms have been in use since Pythagoras.