Sky2Pix_Airy

class astropy.modeling.projections.Sky2Pix_Airy(theta_b=90.0, **kwargs)[source]

Bases: astropy.modeling.projections.Sky2PixProjection, astropy.modeling.projections.Zenithal

Airy - sky to pixel.

Corresponds to the AIR projection in FITS WCS.

See Zenithal for a definition of the full transformation.

\[R_\theta = -2 \frac{180^\circ}{\pi}\left(\frac{\ln(\cos \xi)}{\tan \xi} + \frac{\ln(\cos \xi_b)}{\tan^2 \xi_b} \tan \xi \right)\]

where:

\[\begin{split}\xi &= \frac{90^\circ - \theta}{2} \\ \xi_b &= \frac{90^\circ - \theta_b}{2}\end{split}\]
Parameters
theta_bfloat

The latitude \(\theta_b\) at which to minimize the error, in degrees. Default is 90°.

Attributes Summary

param_names

Names of the parameters that describe models of this type.

theta_b

Methods Summary

evaluate(phi, theta, theta_b)

Evaluate the model on some input variables.

Attributes Documentation

param_names = ('theta_b',)

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.

theta_b = Parameter('theta_b', value=90.0)

Methods Documentation

classmethod evaluate(phi, theta, theta_b)[source]

Evaluate the model on some input variables.