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    Re: Learning/Teaching Celestial on the Net
    From: Frank Reed
    Date: 2010 Nov 7, 15:55 -0800

    Hewitt, you wrote:
    "The recent appearance of the Free Cel Nav site, got me wondering if someone hasn't come up with a virtual sextant. I mean compared to some of the games, how complicated could it be? I see there's a new magic box that lets you operate an on-screen persona. So maybe that doppelgaenger could be swinging a sextant."

    Especially on the most recent devices, something like this is a real possibility. The majority of "smartphones" (pocket computers) now include accelerometers for inclination, magnetic compasses for azimuth orientation, and various means of determining position (even without GPS, if one is in service range, the system can get the exact location of the nearest tower which usually provides a position for the phone accurate to a mile or a few, or in densely populated areas, it can triangulate from wireless Internet signals to get a near-GPS-accuracy position). For a virtual reality simulator of a handheld device like a sextant, the compass is typically too "jumpy". To deal with this, the latest iPhone model has added a gyroscope which, when combined with the compass yields smooth, believable rotation behavior in simulations. So, yes, everything is there.

    What would it look like?? Perhaps something with multiple on-screen views... One view would show the sextant as if in reading position, with the whole instrument visible on its side, with an ability to make gross adjustments of the index arm's position. Another view might show a close-up of the virtual micrometer drum (with a convenient button that lets the device do the reading). And finally there would have to be a "through the telescope" view. This is where the orientation sensors would come into play. You could turn in azimuth, swing the arc, etc. and it should be possible to get it to behave very much like the view through a real sextant. It could be a really great teaching aid.

    You also wrote:
    "I ask because the sextant is the thing that initially attracts people to our quaint old art."

    Yes, absolutely. I have met many students who say 'I want to learn how to use that tool,' excitedly pointing at a fine sextant. Many of these folks are only moderately interested in the calculational details, and in fact, they can become completely turned off by that side of the game. They are attracted to the sextant as a precision instrument.

    And you wrote:
    "Once they've grasped the notion that it's an instrument for accurately measuring angles, they want to try it out. Then, natch, they right away want to know "How'm I doing." I mean, instant gratification is nice."

    I couldn't agree more. This is the key change in the game of navigation education in the past few years. It is MUCH easier to do the calculations on the spot. At the first "lunars" workshop that I did with Don Treworgy back in the fall of 2005 at Mystic Seaport, I made a point of setting up my lunars clearing web pages so that they could be accessed from my old cell phone (which had web access but at a basic level compared to today). So I was able to get the participants to shoot lunars and then, thirty seconds later, I could clear them and tell them just how far out they were in longitude. Instant gratification! It was just amazing being able to tell the first student, who had never even used a sextant before (though he had considerable experience with cameras and telescopes), that his longitude was in error by less than three miles. Perfect, right out of the gate, on the first try.

    You added:
    "At first I just preset the sextant so the sun is a couple of diameters above the horizon and tell them to set its lower edge on the horizon. I don't even go into swinging the arc. Just say that when the knuckles of their fingers go down as they turn the micrometer drum, so does the sun, when they go up, so does the sun. When they have sun on the horizon they say "got it" or "now" or "mark." and I write down the time, turn to the calculator and voila! "Got us within 11 miles first try out of the box. Way to go. Do it again," say I. After a few passes that way - in which everyone shows rapid improvement - comes swinging the arc, etc. And so we go,baby step by baby step. "

    Sounds great! Ya know what ruins "instant gratification" and this style of teaching...? Damn cloudy days. It's a life lesson with respect to celestial navigation, of course, but one sure does need a backup plan when the weather isn't cooperating and a class is scheduled.

    And you concluded:
    "It occurs to me that given a virtual sextant and access to the Net's many calculators, the combination could well give potential cell navigators the instant gratification of knowing they can master that weird gizmo that attracted them in the first place, and give them the confidence to delve further."

    Yes. Just FYI, from a software developer's perspective, the part of this that used to be difficult, namely calculating ephemeris data, virtual altitudes, and all that is relatively easy these days. But building that simulator interface and making it educational and appealing, that's hard and time-consuming. I've noticed that Luis Soltero has released an iPhone version of his StarPilot software. This is not demanding since it's a more or less direct "port" of his calculator-based software. But maybe, since he's already got a product line going, we could con him into making some virtual sextant software... :)


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