Zenithal#

class astropy.modeling.projections.Zenithal(*args, **kwargs)[source]#

Bases: Projection

Base class for all Zenithal projections.

Zenithal (or azimuthal) projections map the sphere directly onto a plane. All zenithal projections are specified by defining the radius as a function of native latitude, $R_{\theta }$.

The pixel-to-sky transformation is defined as:

$$\begin{array}{rl}\varphi & =\arg (-y,x)\\ R_{\theta }& =\sqrt{x^2+y^2}\end{array}$$

and the inverse (sky-to-pixel) is defined as:

$$\begin{array}{rl}x& =R_{\theta }\sin \varphi \\ y& =R_{\theta }\cos \varphi \end{array}$$