Octans – the octant

January 29, 2017


octantThe southernmost constellation in the whole sky, Octans, is named after a celestial navigation instrument called an octant, which is better than a quadrant, but not as good as a sextant, and no where near as good as GPS.

Isaac Newton invented the quadrant which was a handy way of finding your way across an ocean back in the day, but the octant is lighter and easier to aim.

Two guys claim to have invented the octant, Hadley and Godfrey. They probably both did, independently. That happens sometimes. Basically you take Newton’s quadrant and chop it off here, glue on a couple of mirrors there, and up the price. A guy named Campbell did an even better job of chopping and gluing and thus produced the sextant. It is even more expensive so a lot of sailors use the octant for every day stuff and save their shiny new sextant for special occasions.

octThe coolest thing about the constellation is that it is currently smack dab on the bottom of the sky. If there was a south star, like we have a north star, then this is where it would be. The closest thing to a south star at this time is Sigma Octans, which is about one degree from true south, or the width of your index finger held at arm’s length. One degree is considered to be a bit far in pole star terms. Also Sigma Octans is barely visible to the naked eye, so if you are trying to find your way to Antarctica, use a sextant. And take a sweater.

Here’s another navigation tip. On Saturn, the south star is in the constellation of Octans also. It’s Delta Octans. Saturn is the only other planet besides Earth that has its southern pole aimed at Octans. Meanwhile, just as we have a north star but no south star, Saturn has a south star but no north star. On the other hand it does have a weird hexagon shaped cloud around its north pole. And that’s a weird damn deal right there.


Here’s one more amazing fact about the constellation Octans that will amaze your friends. The star Alpha Octans is the dimmest of all the stars named Alpha.

If you are looking for deep sky objects of interest in Octans, look elsewhere. If you are looking for meteor showers, look elsewhere. If you are looking for bright stars, look elsewhere. There should be a constellation named elsewhere so we would always know where to look.


Carpe Noctem

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