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    Re: Corrections for air bubble sextants
    From: Art Leung
    Date: 2022 Jul 30, 14:49 -0700

    Juanjo - congratulations on picking up your aviation bubble sextants. I run a Kollsman regularly for the same reason that you do and get very good results from mine. 

    Sight reduction corrections for a bubble sextant are actually a tiny bit easier than a nautical one because you do not have to account for Dip correction. If you take sights from an aircraft, altitude and coriolus corrections are necessary but if you are on the ground near sea level and stationary you will not need to use these corrections. You just need to apply the standard refraction correction for the height of the object and use 0 for Dip. 

    One thing you will need to do is establish the index correction for your sextant. There are several methods to do this. I find the easiest is to just take several star or sun sights and do a standard reduction. Ideally you will see your Lines Of Position miss your actual position by a fairly constant amount - that average miss amount is your index error. 

    Another consideration is stabilizing the bubble. I shoot from a tripod using a custom made (3D printed) mount.

    You also have a choice to take a shot and record the time (much like a nautical sextant shot) or use the averager built into the sextant and take timed shots. I tend to use the averager because it's fun. I also precompute my shots to be done at a set time  

    If you need help making the power supply or mount, let me know. 

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