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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/4UZVA7DSSF36SHF5BCOTOO6WQXMADPYK/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "4UZVA7DSSF36SHF5BCOTOO6WQXMADPYK",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/VRAZHFDIIVIFCNUWFWMWTVNCYB2X73VE/",
    "sender": {
        "address": "wb4gcs (a) amsat.org",
        "mailman_id": "87014499e012476c8198fad186f7f963",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/87014499e012476c8198fad186f7f963/emails/"
    },
    "sender_name": "Jim Sanford",
    "subject": "[amsat-bb] Re: How to calibrate the azimuth angle?",
    "date": "2007-12-27T23:01:47Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/Q7MG5UWKINLAK5TSI5N66SPOOZLXUEAQ/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "All:\nI have to agree with Franklin . .. . compasses are HARD.   Starting \nwith, it's difficult to get accurate variation & deviation information \n(delta between local magnetic & true North) for land-based locations.\n\nMariners, for centuries, used a now obsolete method of navigation called \n\"celestial\" -- which meant using sun, moon, stars, tables, and \ncalculations to determine location based on observations.\n\nOne of those techniques was known (at least 35 years ago, when I first \nstudied celestial Nav) as \"Local apparent Noon\".  You started with an \nestimate of your latitude, determined a time offset from the center of \nthe time zone based on assumed (dead-reckoning) position, and then \nstarted some time PRIOR.  Using a sextant, you would start \"swinging\" \nthe sun, and click a stopwatch (synchronized to WWV) at the highest \nelevation of sun.  You have now determined the time when the sun's \nelevation is highest, or Local Apparent Noon.  From that, you could \ndetermine longitude, and latitude using other techniques.\n\nThis process lends itself nicely to reverse engineering as follows:\n1.  Using your handy GPS, determine the most precise coordinates for \nyour tower/antenna.\n2.  Synchronize your laptop or computer clock with any of the internet \ntime servers.\n3.  Synchronize your watch with the laptop/computer.\n4.  Enter the pre-determined coordinates into your favorite tracking \nprogram (InstantTrack, Nova, SATPC32 . . . .)\n5.  Using the \"fast forward\" feature of that tracking program, move \nuntil you get sun azimuth of 180 degrees.  This should coincide with \nmaximum elevation.\n6.  Write down the time of max elevation/180 degree azimuth.\n7.  Stand \"north\" of your tower/antenna at about that time, with a stick \nor other marker.\n8.  When your watch indicates the appointed time, put the stick in the \nground at the far extent of the shadow from your antenna/tower.\n9.  You just marked true North at your location. \n\nObviously the taller your antenna, and longer your shadow, the more \naccurate your marking will be.  For any reasonable antenna height, this \nwill be well within the accuracy of any reasonable amateur antenna system.\n\nI have done this, and it matched PRECISELY with the direction determined \nusing (difficult to determine) local variation and deviation vs. \nmagnetic.  I had the luxury of an open field, so suspect very little \ninterference to the magnetic compass from \"local\" effects.\n\nFrankly, I find the celestial method easier, and more repeatable, \nparticularly at Field Day sites, etc.\n\nGood luck & 73,\nJim\[email protected]\n\n\nOllie Eisman wrote:\n> Franklin Antonio wrote:\n> ...\n>   \n>> Compasses are very difficult to use to get an accurate \n>> direction.  \n>>     \n>\n> I've always had excellent results with a Brunton compass.  It takes a \n> few minutes to learn how to use one but it's well worth it.\n>\n> http://en.wikipedia.org/wiki/Brunton_compass\n>\n> Ollie, AJ1O\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n>   \n",
    "attachments": []
}