Re: Complicated Question about sky geometry

From: Björn Gimle (bjorn.gimle@gmail.com)
Date: Tue Sep 11 2012 - 18:24:33 UTC

  • Next message: Kevin Fetter: "Echostar 2"

    To conclude (?) this exercise I created an Excel spreadsheet
    https://sites.google.com/site/starrymdnytt/dokument-och-l%C3%A4nkar/Angles%20and%20great%20circles.xls
    which can compute points along the great circle ("straight line") between
    two coordinate pairs.
    I added these to SkyMap's deepsky.txt (decimal RA(h)) and updated the
    stereographic plot, added rectangular and polar at the link below.
    19.44933    10.74753457
    18.97737    12.79970885
    18.42632    14.91765471
    17.80308    16.91239078
    17.13095    18.55102762   (mid-point RA/Dec; 212.29/62.19 az/alt)
    16.44803    19.64656023
    15.79609    20.14455279
    15.20673    20.13009617
    14.69479    19.7593865
    
    /Björn
    
    2012/9/9 Björn Gimle <bjorn.gimle@gmail.com>
    
    > ...From that centre point, it's easy to locate the point 10 degrees below.
    > In Skymap you can quickly switch projection to read the RA/dec of the
    > center point
    > (about 17:06 +18:10) and the az/alt (about 212.9 / 61.9)
    > ...
    > You can also use spherical trigonometry to compute the midpoint
    > coordinates.
    >
    > (Another way is to create fake observations at Altair and Arcturus of
    > a very low altitude orbit, and plot that satellite track)
    >
    > Some demo maps, dated 2012-09-09, are at the very bottom of page
    > https://sites.google.com/site/starrymdnytt/Hem/intresseomraaden?pli=1
    >
    > --
    ----------------------------------------
    Björn Gimle, COSPAR 5919
    59.2576 N, 18.6172 E, 23 m
    Phone: +46 (0)8 571 43 312
    Mobile: +46 (0) 704 385 486
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