# Sky2Pix_SlantOrthographic¶

class astropy.modeling.projections.Sky2Pix_SlantOrthographic(*args, **kwargs)[source]

Slant orthographic projection - sky to pixel.

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.

$R_\theta = \frac{180^{\circ}}{\pi}\cos \theta$

But more specifically are:

$\begin{split}x &= \frac{180^\circ}{\pi}[\cos \theta \sin \phi + \xi(1 - \sin \theta)] \\ y &= \frac{180^\circ}{\pi}[\cos \theta \cos \phi + \eta(1 - \sin \theta)]\end{split}$

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)