class astropy.modeling.projections.Pix2Sky_SlantOrthographic(xi=0.0, eta=0.0, **kwargs)[source]

Bases: astropy.modeling.projections.Pix2SkyProjection, astropy.modeling.projections.Zenithal

Slant orthographic projection - pixel to sky.

Corresponds to the SIN projection in FITS WCS.

See Zenithal for a definition of the full transformation.

The following transformation applies when \(\xi\) and \(\eta\) are both zero.

\[\theta = \cos^{-1}\left(\frac{\pi}{180^{\circ}}R_\theta\right)\]

The parameters \(\xi\) and \(\eta\) are defined from the reference point \((\phi_c, \theta_c)\) as:

\[\begin{split}\xi &= \cot \theta_c \sin \phi_c \\ \eta &= - \cot \theta_c \cos \phi_c\end{split}\]
xi : float

Obliqueness parameter, ξ. Default is 0.0.

eta : float

Obliqueness parameter, η. Default is 0.0.

Attributes Summary


Methods Summary

evaluate(x, y, xi, eta) Evaluate the model on some input variables.

Attributes Documentation

eta = Parameter('eta', value=0.0)
param_names = ('xi', 'eta')
xi = Parameter('xi', value=0.0)

Methods Documentation

classmethod evaluate(x, y, xi, eta)[source]

Evaluate the model on some input variables.