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    Re: Curious star charts
    From: Alexander Duytschaever
    Date: 2020 Nov 20, 07:37 -0800

    The number at the bottom center seems to be a Right Ascension reference.

    Looking at slide with RA19.0 labeled at the bottom, it seems that the delta time from Altair (~0:17) to Sirius/Procyon (~0:58) is 0:41. On a star map, that distance covers (along a great circle, the center lines look like great circles) ~170 degrees, which makes 360 degrees cover in 1h26m. 

    According to https://keisan.casio.com/exec/system/1224665242, this would represent an orbit of about h=90km.


    Some ideas that crossed my mind:

    • 90km seems to be called the "Karman Line", limit of atmosphere
    • SR71? too low (up to 100kft = 33km)
    • some kind of Moon orbit tool (Apollo? Lunar Escape System?), but these start at 1.8h = 1h48m
    • short range ballistic missile defence?

    It might be good to add a known object or a ruler to the pics, to get an idea of scale.

    rgds

    -alex-

       
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