This 2D coordinate system corresponds to the celestial coordinate system, whose axes are defined in terms of the earth (Right Ascension is analogous to Longitude and Declination is analogous to Latitude). The same comments about spherical and tangent plane coordinate systems apply here, reading Dec for El and RA for Az.
As can be seen from See Telescope coordinate systems looking towards sky (excludes Nasmyth foci) , the (RA,Dec) coordinate system is left-handed when looking towards the sky. The directions are conventionally labeled "E" (for "East", the direction of increasing RA) and "N" (for "North", the direction of increasing Dec).