EllipseAnnulusSkyRegion

class regions.EllipseAnnulusSkyRegion(center, inner_width, outer_width, inner_height, outer_height, angle=<Quantity 0. deg>, meta=None, visual=None)

Bases: AsymmetricAnnulusSkyRegion

A elliptical annulus in SkyCoord coordinates.

Parameters:

centerSkyCoord

The position of the center of the elliptical annulus.

inner_widthQuantity

The inner width of the elliptical annulus (before rotation) as an angle.

outer_widthQuantity

The outer width of the elliptical annulus (before rotation) as an angle.

inner_heightQuantity

The inner height of the elliptical annulus (before rotation) as an angle.

outer_heightQuantity

The outer height of the elliptical annulus (before rotation) as an angle.

angleQuantity, optional

The rotation angle of the elliptical annulus, measured anti-clockwise. If set to zero (the default), the width axis is lined up with the longitude axis of the celestial coordinates.

metaRegionMeta or dict, optional

A dictionary that stores the meta attributes of the region.

visualRegionVisual or dict, optional

A dictionary that stores the visual meta attributes of the region.

Attributes Summary

angle	The rotation angle measured anti-clockwise as a astropy.units.Quantity angle.
center	The center position as a astropy.coordinates.SkyCoord.
inner_height	The inner height (before rotation) as a astropy.units.Quantity angle.
inner_width	The inner width (before rotation) as a astropy.units.Quantity angle.
outer_height	The outer height (before rotation) as a astropy.units.Quantity angle.
outer_width	The outer width (before rotation) as a astropy.units.Quantity angle.

Methods Summary

to_pixel(wcs)	Return the equivalent region defined in pixel coordinates.
to_polygon(wcs[, n_points])	Return a CompoundSkyRegion of two PolygonSkyRegion objects that approximates this annulus.
to_spherical_sky([wcs, ...])	Convert to an equivalent spherical SphericalSkyRegion instance.

Attributes Documentation

angle

The rotation angle measured anti-clockwise as a astropy.units.Quantity angle.

center

The center position as a astropy.coordinates.SkyCoord.

inner_height

The inner height (before rotation) as a astropy.units.Quantity angle.

inner_width

The inner width (before rotation) as a astropy.units.Quantity angle.

outer_height

The outer height (before rotation) as a astropy.units.Quantity angle.

outer_width

The outer width (before rotation) as a astropy.units.Quantity angle.

Methods Documentation

to_pixel(wcs)

Return the equivalent region defined in pixel coordinates.

Parameters:

wcsWCS

The world coordinate system transformation to use to convert between sky and pixel coordinates.

Returns:

pixel_regionPixelRegion

A pixel region.

Notes

The conversion between sky and pixel coordinates is an approximation. The sky region shape is mapped to a pixel region shape using the local pixel scale and angle at the region center. Projection effects over the extent of the region are not accounted for. The region shape type is always preserved (e.g., a CircleSkyRegion converts to a CirclePixelRegion).

For WCS with distortions (e.g., SIP), the local Jacobian matrix of the WCS transformation is used to compute directional scale factors and angle. For WCS without distortions, a local pixel scale and angle are computed using offset-based methods.

to_polygon(wcs, n_points=100)

Return a CompoundSkyRegion of two PolygonSkyRegion objects that approximates this annulus.

Parameters:

wcsWCS

The WCS to use for the sky-to-pixel-to-sky conversion.

n_pointsint, optional

The number of polygon vertices for each ellipse. Default is 100.

Returns:

polygonCompoundSkyRegion

A compound region of two polygon regions approximating the annulus.

to_spherical_sky(wcs=None, include_boundary_distortions=False, n_points=None)

Convert to an equivalent spherical SphericalSkyRegion instance.

Parameters:

wcsWCS instance, optional

The world coordinate system transformation to use to convert between sky and pixel coordinates. Required if transforming with boundary distortions (if include_boundary_distortions is True). Ignored if boundary distortions not included.

include_boundary_distortionsbool, optional

If True, accounts for boundary distortions in spherical to planar conversions, by discretizing the boundary and converting the boundary polygon. Default is False, which converts to an equivalent idealized shape.

n_pointsint, optional

The number of polygon vertices for boundary discretization. This keyword will have effect unless include_boundary_distortions=True. Default is 100.

Returns:

spherical_sky_regionSphericalSkyRegion

A spherical sky region, with an equivalent shape (if include_boundary_distortions is False), or a discretized polygon of the boundary (if include_boundary_distortions is True).