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Comment by brightball | Hacker News Reader

I talked to a guy a few weeks ago who worked for a company that developed a guidance system before GPS that used stars like a sextant to navigate.

Pretty crazy to think about.

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Something in that vein that has always amazed me, even though its performance in the field left something to be desired, is the Norden bombsight [0].

"The Norden [used] an analog computer that continuously recalculated the bomb's impact point based on changing flight conditions, and an autopilot that reacted quickly and accurately to changes in the wind or other effects."

0: https://en.wikipedia.org/wiki/Norden_bombsight

Spacecraft often use stars to orient themselves. The Voyager spacecraft have star trackers to keep the antenna pointing at Earth. They look for the Canopus star.

Don't they need more than 1 star to get an orientation? I mean other than brightness 1 star doesn't give you a lot of information?

I guess if they can confirm that it is a specific star they know where on a I finite line they are. If that line happens to be through earth and the space craft they know where to point their antenna.

Yes, I think the tracker also uses the sun as I remember reading.

This is still important, e.g. the Navy teaches celestial navigation in case GPS is disrupted.

https://www.thedrive.com/the-war-zone/3865/this-is-likely-wh...

It is also common in shiprepair to use the stars for aligning equipment with a theodolite like device.

GPS and celnav (and other forms of navigation, radio or otherwise) are really not so different when you get down to fundamentals. At their core they are all about locating the intersection of multiple lines, circles, or spheres of position, depending on how many dimensions you're working with. The major differences are in how you come up with the LOPs.

The odd man out, if you will, is inertial nav, which has more in common with dead reckoning.

Star trackers https://en.m.wikipedia.org/wiki/Star_tracker

Ironically, the last one I touched was a piece of donated Russian equipment, intended for spacecraft use, with no manual.

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