Pix2Sky_SlantOrthographic

class astropy.modeling.projections.Pix2Sky_SlantOrthographic(*args, **kwargs)

Bases: Pix2SkyProjection, 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:

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

Parameters:

xipython:float

Obliqueness parameter, ξ. Default is 0.0.

etapython:float

Obliqueness parameter, η. Default is 0.0.

Attributes Summary

eta
param_names	Names of the parameters that describe models of this type.
xi

Attributes Documentation

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

param_names = ('xi', 'eta')

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.

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