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    Aviation Bubble Sextant
    From: mjans
    Date: 2010 Aug 27, 14:41 -0700

    Hello,

    I have recently acquired my grandfathers WWII Bubble sextant. He has long passed away and left me no instruction on how to use it. No manuals, no spoken wisdom, nada... I've figured out how to make the bubble and how to collapse it, etc.. but still haven't quite figured out what corrections I need to apply to the sighting. When figuring out Ha from Hs, would I need to apply an Index correction? Since there doesn't seem to be an index mirror, I don't really see why?

    When taking a sighting, how big should the bubble be and where do I place the object? In the bubble or on top? This one seems to have a timer too, is there anyway to mechanically change the timing interval? It seems to only take a sight for about a minute!

    Assuming I was in an old DC-3 flying at 5000 ft, taking a LAN sight... What corrections would I apply.. I assume, temperature, pressure and altitude (pressure or density alt??) but would airspeed apply too? If so.. True Airspeed or Ground Speed? Would the correction be altitude only instead of Dip? If I have to correct for altitude, are there tables?

    Hoping you can help me shed some light...

    Thanks

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