# Pix2Sky_CylindricalPerspective¶

class astropy.modeling.projections.Pix2Sky_CylindricalPerspective(mu=1.0, lam=1.0, **kwargs)[source]

Cylindrical perspective - pixel to sky.

Corresponds to the CYP projection in FITS WCS.

$\begin{split}\phi &= \frac{x}{\lambda} \\ \theta &= \arg(1, \eta) + \sin{-1}\left(\frac{\eta \mu}{\sqrt{\eta^2 + 1}}\right)\end{split}$

where:

$\eta = \frac{\pi}{180^{\circ}}\frac{y}{\mu + \lambda}$
Parameters
mufloat

Distance from center of sphere in the direction opposite the projected surface, in spherical radii, μ. Default is 1.

lamfloat

Attributes Summary

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

Methods Summary

 evaluate(x, y, mu, lam) Evaluate the model on some input variables.

Attributes Documentation

lam = Parameter('lam', value=1.0)
mu = Parameter('mu', value=1.0)
param_names = ('mu', 'lam')

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.

Methods Documentation

classmethod evaluate(x, y, mu, lam)[source]

Evaluate the model on some input variables.