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How to get distances to stars: Parallax
From the text, Horizons by Seeds
The angular diameter here is
“p” – the “parallax” in arcsec.
The linear diameter is 1 AU.
d = 206265/p in AUs
d = 1/p in units of “parsecs”
1 parsec or 1pc = 206265 AU
1 pc = 3.26 light years