<p>I am trying to find the position angle of a star whose Ra and dec are known. I have already looked at the <a href="https://astronomy.stackexchange.com/questions/25306/measuring-misalignment-between-two-positions-on-sky">'Measuring misalignment between two positions on sky'</a> question and answer, but the answer gives an undefined solution if one of the points is the North Celestial Pole (NCP). I would appreciate if anyone could tell me how to find an object's position angle given its equatorial coordinates. </p>

CC BY-SA 4.0
2020-06-02T14:12:02.663Z
The position angle is the angle between three points: two objects (such as two stars in a double star) and the north celestial pole (NCP). It sounds like you only have one star, so position angle is not applicable. Are you asking for a different angle? Perhaps the parallactic angle? (Parallactic angle is the angle between NCP and the zenith.)
JohnHoltz
CC BY-SA 4.0
2020-06-02T15:18:29.013Z
You've identified a degenerate case, and the formula in [JohnHoltz's answer](/a/25330) to the linked question reflects that. The direction from NCP to itself is undefined.
Mike G
CC BY-SA 4.0
2020-06-03T09:29:11.260Z
@JohnHoltz  Ah, thank you. The question gave information about two stars but asked 'what is the position angle of the secondary star with respect to north', which means I need to include the other star as well. Thanks again.
Physics
<coordinate><positional-astronomy><astrometry>
Position Angle Relative to North
Physics
# Position Angle Relative to North

(Asked by: username_0 on 2020-06-02)

I am trying to find the position angle of a star whose Ra and dec are known. I have already looked at the ['Measuring misalignment between two positions on sky'](https://astronomy.stackexchange.com/questions/25306/measuring-misalignment-between-two-positions-on-sky) question and answer, but the answer gives an undefined solution if one of the points is the North Celestial Pole (NCP). I would appreciate if anyone could tell me how to find an object's position angle given its equatorial coordinates.

**Tags:** coordinate, positional-astronomy, astrometry
> **Comments:**
> **username_1**: The position angle is the angle between three points: two objects (such as two stars in a double star) and the north celestial pole (NCP). It sounds like you only have one star, so position angle is not applicable. Are you asking for a different angle? Perhaps the parallactic angle? (Parallactic angle is the angle between NCP and the zenith.)  
> **username_2**: You've identified a degenerate case, and the formula in [JohnHoltz's answer](/a/25330) to the linked question reflects that. The direction from NCP to itself is undefined.  
> **username_0**: @JohnHoltz  Ah, thank you. The question gave information about two stars but asked 'what is the position angle of the secondary star with respect to north', which means I need to include the other star as well. Thanks again.  

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