An accident of lighting uncovers origins of the astrolabe
nautil.us
nautil.us
Writing this on a sailboat right now, with gps and internet, crazy how quickly things change but also stay the same
Edit: it’s also so fascinating how the unit was altered over time and re-enscribed/calibrated. Hardware updates! Reminds me of some posts recently about imaging ancient scrolls and reading the original but erased text/script
As it'd be foolish to rely on things like gps that may no longer be around when you want/need to launch, as far as I know ICBMs (and presumably also SLBMs?) still shoot the stars near apogee, to fix their reckoning.
The astro-nav's gimbaled telescope-like system on top of the guidance group works by making an ever-widening circular search pattern to find and fix three of any of 64 mapped stars in its memory, and compares their locations to a Julian calendar and a highly accurate chronometer.
https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-w...
https://timeandnavigation.si.edu/multimedia-asset/nortronics...
>With its provenance, this astrolabe is one of the earliest Islamic astrolabes documented in early modern Italy still preserved today.
...
>The astrolabe is Andalusian, and from the style of the engraving and the arrangement of the scales on the back, it can be compared to instruments made in Spain in the eleventh century. The astrolabes made in Toledo by Ibrāhīm ibn Saʿīd al-Sahlī during the period of the Taifa (ca. AD 1018–1085) present similarities...