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AstroNavigation – A free course (vanderbilt.edu)
299 points by jweir 11 months ago | hide | past | web | favorite | 38 comments

For anyone interested in natural navigation in general, you might check out The Lost Art Of Finding Our Way: https://www.goodreads.com/book/show/16241535-the-lost-art-of...

I also highly recommend "Finding your way without map or compass"


Anybody know where to buy a good sextant? (I hope the course discusses this; I haven't had time to read it yet.) I started trying to learn this stuff a few months ago and it seems that most available sextants fall into two categories: Cheap plastic ones with poor thermal characteristics that make them inaccurate, and expensive brass ones that are more thermally stable but designed for display and not calibrated for serious navigation. I'd like to buy one in between: A quality navigational instrument that doesn't have to be "pretty".

I would suggest subscribing to navlist at fer3.com, and reading through the many old threads there about this subject to get a general idea. In my experience the good and the bad sextants are all mixed on the auction sites. You can always post a picture there before you buy...

Personally I'd never buy a new one, since a second hand one is just as good (if you have a bit of knowledge and avoid broken ones). A sextant doesn't need calibration beyond what's done at the factory and what you can do yourself. On top of that most have been very lightly used.

If you're interested in the instrument itself (rather than simply how to use it as a tool), 'The Nautical Sextant' by Bill Morris is a superb book: https://www.amazon.com/Nautical-Sextant-W-J-Morris/dp/093983... .

Good suggestions from others and I know this is not your use case but I'd add to anyone new to navigation or with just a casual interest: get a plastic 'emergency sextant' and try using it along with a digital watch (Casio cheap one). Davis and EBBCO do both do plastic sextants.

There is even a book on how to use them called "How to Use Plastic Sextants" by David Burch who seems to be a fairly prolific author on celestial navigation http://a.co/0iVNVrW

Linked to that book page on Amazon is the Davies 'quick reference card' (laminated) that I imagine one would have in the life boat...

This site seems to have a good selection: https://www.celestaire.com/ . A person commenting in the San Francisco Amateur Astronomers facebook page where I posted this course mentioned they have an Astra III-B

Any good nautical store should have them. Obviously, you'll find those only at the coasts or near rivers.

I can recommend American Nautical Services[0].

[0] https://www.amnautical.com

Harbor freight used to sell a brass one. Haven't checked in a while, but it might be something nice.


That is a typical 'decorative object', not a sextant fit for purpose. They've been flooding auction sites in hundreds of variations, often 'antiqued' and made to look superficially like real 150 year old sextants.

Imagine staring into the sun through that telescope using only that coloured green glass as a filter. Goodbye retina!

I always wanted to learn something like this! Embarrassingly... I never knew what it was called until today so I never found any books or videos on it. Learning what it is called and about an free course online course is awesome!

It's also referred to as celestial navigation.

Your local chapter of the United States Power Squadrons (now re-branding to America's Boating Club) teaches this.

Is it a one time fee or is there a club I have to join first?

Good question. It used to require a membership (I think it's like $70/year); then there is a fee for the course on top. I believe now they have opened the courses up to the public.

There are two courses, actually. The first one focuses on sun sights- I've had that one. The second uses other stars. It's really for marine folks- so it includes a lot of navigation stuff.


Awesome, thanks!!

I found this course somewhat lacking in intuition building.

It's also sad that we're still using trig tables (that's essentially what the nautical Alamanac is. It also has to be updated every year). I thought the aeronautical paper flight computer was complex ...

Also, I find it hard to believe that a set of 6 books is more disaster proof (and quicker to use) than a hardened calculator for when the shit hits the fan ...

FWIW, here is a nice free resource for printing your own almanac:


Why is looking things up in a table sad?

For the purpose of astro nav: NP303 is calculated for an epoch of 5 years (and it's only 3 books). Until its end of life, it has to be "updated" in the sense that corrections need to be applied as they are released.

I don't think the point of the books has ever been disaster proofing. For the most part, books were good enough for the job before computers and still are. They're cheap, come from trusted sources (and it's easy to verify that they're legitimate), and they're easy to correct should they have errata.

Windows PCs and excel spreadsheets are used in navigation all the time. Nobody's forcing navigators to use books. If they do, though, they probably have a good reason for it.

If we are to go much further on the technological side of this, I have to wonder: rather than just using a calculator rather than a table, what could be done with just a phone that could combine software with a clock, an accelerometer, and a camera?

I failed this course 13 times so I've remained a Second Technician in the Space Corps.

At least you have your Bronze Swimming Certificate.

Cool, I was thinking of learning this recently. I also wanted to find a book on amateur astronomy but still have no idea what exactly to look for.

One of my favourite books is Turn Left at Orion by Guy Consolmagno. It describes the different astronomical objects that you can expect to see and how to find them in the sky. I think it also does a good job of setting expectations because you just won't see Hubble class images from your backyard. The is also a companion website http://www.cambridge.org/features/turnleft/

I can second this recommendation, if you are into backyard astronomy.

Turn Left at Orion is a popular suggestion (see sibling comment) but the other question is what do you want to do, what part of astronomy interests you? Amateur astronomy is a vast field and depending on what you're interested in, you'll go in different directions. Do you want to look at the Moon? Planets? Galaxies? And so on. Of course, you probably need a starting point which a good book can provide. See if you have a local astronomy club you can go visit, they will usually have events where you can use telescopes and talk to experienced folks. You can also poke around on Cloudy Nights (www.cloudynights.com), by far the largest amateur astronomy forum online.

I've used Redshift since I taught astronomy. The mobile app is very good.

Me too! I've also been looking for an astronomy app that's not super complex, and not like a projection of the sky, just a list: "What's in the sky tonight," ordered by most-commonly-wondered about. Like "1) If you look to the West you'll probably see Venus."

I’ve been happy with Sky Guide over the years. It’s not a list but it tells you what you’re looking at and you can set it to arbitrary times and locations. Like I can know what my girlfriend would see in Argentina tonight while sitting in my apartment in the US.

It is a projection and not a list but it’s very handy and helps you identify objects better than a list would.

NightWatch by Terence Dickinson is often recommended.

Boy scouts orienteering merit badge stuff.

For you downvoters, I was in the Boy Scouts and earned the Orienteering merit badge.

Eagle Scout here. So was I, but your experience seems atypical. You probably just had a Merit Badge counselor that went above and beyond. That's awesome!

Anyone who wants to give back and help the shape the next generation, you can be a Merit Badge counselor. Just talk to your local council. There's over a 100 Merit Badges, and more than half of them are STEM-related. If you have a career or hobby that's related to one of them, you can share your knowledge, skills, and advice to others.


Unless it’s changed the orienteering badge was about topo maps and compasses 20 years ago. The requirements (pamphlet isn’t free, but requirements are online) seem to indicate that’s still true. This course covers something different and more complex than what the scouts taught us.


I was in the Boy Scouts and did orienteering, but I don't remember using a sextant, chronometer, and sight reduction tables :).

I watched the first couple videos but stopped when they started a practical example (3rd video, I think). Turns out you need some basic tools I don't have (dividers, parallel rulers) and charting paper. They don't mention this upfront. I need to perform the steps they demonstrate in order to have it sink in so I stopped watching. The tutorial is interesting enough that I'll see if I can get the necessary things and pick it up again.

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