# 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
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
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
> ...
> 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
>
> --
----------------------------------------
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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