Conic¶
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class
astropy.modeling.projections.
Conic
(*args, meta=None, name=None, **kwargs)[source] [edit on github]¶ Bases:
astropy.modeling.projections.Projection
Base class for conic projections.
In conic projections, the sphere is thought to be projected onto the surface of a cone which is then opened out.
In a general sense, the pixel-to-sky transformation is defined as:
\[\begin{split}\phi &= \arg\left(\frac{Y_0 - y}{R_\theta}, \frac{x}{R_\theta}\right) / C \\ R_\theta &= \mathrm{sign} \theta_a \sqrt{x^2 + (Y_0 - y)^2}\end{split}\]and the inverse (sky-to-pixel) is defined as:
\[\begin{split}x &= R_\theta \sin (C \phi) \\ y &= R_\theta \cos (C \phi) + Y_0\end{split}\]where \(C\) is the “constant of the cone”:
\[C = \frac{180^\circ \cos \theta}{\pi R_\theta}\]Attributes Summary
delta
param_names
sigma
Attributes Documentation
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delta
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param_names
= ('sigma', 'delta')¶
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sigma
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