Representing Celestial Coordinate Systems - 9
Mercator projection: celestial coordinates in red -
native coordinates in grey

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  • Complication - native coordinates of the reference point differ for different projections.

    • Zenithal projections:


    • Cylindrical, pseudo-cylindrical, polyconic, quad-cube and some other projections:


    • Conic projections:


  • Consequently, the mathematical relationship between the Euler angles and CRVALi differs for different projection types.


  • Nevertheless, the first-order behaviour of the celestial coordinate system is similar at the reference point.


  • Additional FITS keywords:   PVi_m.