Hi fellows!
Could you please solve this little doubt of mine: I’m intending to
make a cylindrical “bottle” sundial, which would show the acronychal
rising of some stars. But, how can I calculate the nearest day when
the perfect opposition between the sun and a given star occurs? I
mean, what’s the best way to define it? When there are 12 sidereal
hours of difference between their right ascensions, or when their
ecliptic longitudes have a difference of 180°? I’ve tried both
methods, and found that they can produce a difference as great as 6
days between results.
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