Pix2Sky_ZenithalPerspective

class astropy.modeling.projections.Pix2Sky_ZenithalPerspective(*args, **kwargs)

Bases: Pix2SkyProjection, Zenithal

Zenithal perspective projection - pixel to sky.

Corresponds to the AZP projection in FITS WCS.

\[\begin{split}\phi &= \arg(-y \cos \gamma, x) \\ \theta &= \left\{\genfrac{}{}{0pt}{}{\psi - \omega}{\psi + \omega + 180^{\circ}}\right.\end{split}\]

where:

\[\begin{split}\psi &= \arg(\rho, 1) \\ \omega &= \sin^{-1}\left(\frac{\rho \mu}{\sqrt{\rho^2 + 1}}\right) \\ \rho &= \frac{R}{\frac{180^{\circ}}{\pi}(\mu + 1) + y \sin \gamma} \\ R &= \sqrt{x^2 + y^2 \cos^2 \gamma}\end{split}\]

Parameters:

mupython:float

Distance from point of projection to center of sphere in spherical radii, μ. Default is 0.

gammapython:float

Look angle γ in degrees. Default is 0°.

Attributes Summary

gamma
mu
param_names	Names of the parameters that describe models of this type.

Attributes Documentation

gamma = _ParameterDS('gamma', value=0.0)

mu = _ParameterDS('mu', value=0.0)

param_names = ('mu', 'gamma')

Names of the parameters that describe models of this type.

The parameters in this tuple are in the same order they should be passed in when initializing a model of a specific type. Some types of models, such as polynomial models, have a different number of parameters depending on some other property of the model, such as the degree.

When defining a custom model class the value of this attribute is automatically set by the Parameter attributes defined in the class body.