# How do I calculate the cartesian coordinates of stars

Given the Right ascension in h m s, Declination in deg ' " and the Trigonometric parallax How can I get the cartesian (x,y,z) coordinates of a star? I'm guessing I need 3 separate formulas to get each x, y and z values.

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Why do you need Cartesian coordinates? In any event... – J. M. Dec 23 '10 at 10:09
Then your declination corresponds to $\theta$, right ascension to $\phi$ and parallax to $r$ for a properly referenced spherical coordinate system. See en.wikipedia.org/wiki/Spherical_coordinate_system – Ross Millikan Dec 23 '10 at 14:15
@J.M. to plot thing in openGL you need Cartesian coordinates. @Ross - Thanks I'll look into it. – Justin808 Dec 24 '10 at 20:16

I know this is old, but here is the answer:

http://fmwriters.com/Visionback/Issue14/wbputtingstars.htm

A = (RA_hours * 15) + (RA_minutes * 0.25) + (RA_seconds * 0.004166)

B = ( ABS(Dec_degrees) + (Dec_minutes / 60) + (Dec_seconds / 3600)) * SIGN(Dec_Degrees)

C = distance in light years or parsecs

Cartesian:

X = (C * cos(B)) * cos(A)

Y = (C * cos(B)) * sin(A)

Z = C * sin(B)

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