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    Re: Aviation Bubble Sextant
    From: Ken Gebhart
    Date: 2010 Aug 27, 17:32 -0500

    mjans,
    
    How about telling us exactly what model sextant you have?  It makes a
    difference when positioning the body with respect to the bubble.
    
    Ken Gebhart
    On Aug 27, 2010, at 4:41 PM, mjans wrote:
    
    > 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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