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    Re: Relearning CelNav and Lunars for Antarctica
    From: Frank Reed
    Date: 2019 Oct 12, 11:20 -0700

    Chris Lamousin, you wrote:
    "I am going to be going from the southern tip of South America to Antarctica this December."

    I often try to emphasize when I teach my Modern Celestial Navigation class (three sessions in the next four weeks) that we in the 21st century can take advantage of the constraints that our schedules place on us. Within a small range of options, we almost always know in advance our approximate locations on specific dates. Do you know what date you will be leaving from southern South America?

    We can simulate the sky easily for the dates of your trip. Of course weather may delay you by a couple of days, but the simulation will be close enough. In early/mid December, departing from Punta Arenas, Chile or Ushuaia, Argentina, you would find the famous nearby star Alpha Centauri (now known officially by the navigators' name: Rigil Kentaurus) on the meridian, due south, in that long Antarctic evening twilight. The Southern Cross will be on its head to the left of Alpha Centauri. Meanwhile, Orion will be easy to find, as always, but in this latitude he's standing on his head. Simple star-finding tricks that work in the northern hemisphere still work down there: draw a line through the Belt of Orion. Follow it "left" to Aldebaran, or follow it "right" to brilliant Sirius. From there you can find Canopus, too. The night will be short, and by morning twillight the stars will have rotated around only about 60°: Alpha Centauri now in the southeast, Orion nearly due north.

    Try for star sights on your first few evenings. As you travel south, the Southern Cross and Alpha Centauri will rise while Orion falls, and meanwhile the Sun's low point below the horizon will rise steadily. Below about 61-62°S, twilight will last all night, and you won't see any stars. You can take Sun sights for 16 hours or more every day.

    The motions of the stars run like clockwork. The weather? Not clockwork, but it has some predictable behavior, too. If you're lucky, you may see some stars during your trip. It's also possible that you will see leaden overcast skies every day. Fortunately, there may be other distractions. :)

    You mentioned that you had learned celestial navigation from Don Treworgy back in the 1990s using Sue Howell's book. What you learned back then is a particular form of celestial that has been stable (or viewed differently, "stagnant") since the late 1970s. I sometimes call it "disco navigation". That type of navigation takes weeks to learn and focuses on many fine details of the traditional kit of tools. It can become a rote ritual, and that may be why you're thinking that you won't work up your sights until you get home. If you do that, at least use an app to test your sights. All too often, when there's no immediate feedback, navigation experiments fall flat because some simple issue was overlooked while taking the sights.  

    Why do celestial navigation by 1970s methodologies today? Many licensing exams require antiquated methods in large measure because the people designing the exams are themselves antiquated. But are we taking sights just to pass an exam? Or are we navigators? If we're navigating, then we can accomplish much the same with less cumbersome methods. In my two-day class, we skip over all the trivialities of the tables that became essential elements of "disco navigation". The type of navigation I teach requires no delicate plotting steps, no thick volumes of tables or data. With a $10 solar-powered handheld calculator, six pages of almanac data, and (sometimes) one plot on common graph paper, you can get an excellent fix in minutes.

    Frank Reed
    Clockwork Mapping / ReedNavigation.com
    Conanicut Island USA

    PS: Glad you found the NavList message boards. Do continue asking questions, and tell the group more about your adventure. You'll get many more replies, I am sure. :)

       
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