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Add position angle functionality #1

cdeil opened this Issue · 5 comments

2 participants


It would be nice if you could add the following functionality to pyephem:

  • Compute the position angle between two points in a given coordinate system (namely Equatorial or Galactic or AltAz).
  • Transform a position angle in one coordinate system (e.g. AltAz) to another (e.g. Galactic).

When implemented please mention it in this stackoverflow question:


Thank you for writing up this issue! I should have some spare cycles next week — after this weekend's DjangoDash — to look at creating a solution.


I'm hoping this feature will become in astropy.coordinates (astropy/astropy#2311).


Instead of trying to do that in PyEphem — whose mission I have now more narrowly defined as simply wrapping the old astronomy logic inside of libastro — I am going to attempt this functionality inside of Skyfield instead, so I am going to close this ticket and focus my future work there, since it is a pure-Python astronomy library (except for needing NumPy) that should be easier to advance and improve:


(And, feel free to drop a link here if you did get around to adding this to astropy!)


Position angle computation is available in astropy here, position angle transformation to other coordinate systems is not.

If you do implement this in skyfield, that would be great.

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