CircleAnnulusSphericalSkyRegion

class regions.CircleAnnulusSphericalSkyRegion(center, inner_radius, outer_radius, meta=None, visual=None)

Bases: AnnulusSphericalSkyRegion

Class for a circular annulus sky region, where the circular annulus is interpreted within a spherical geometry reference frame.

Parameters:

centerSkyCoord

The center position.

inner_radiusQuantity

The inner radius in angular units.

outer_radiusQuantity

The outer radius in angular units.

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

center	The center position as a astropy.coordinates.SkyCoord.
inner_radius	The inner radius as a astropy.units.Quantity angle.
meta	The meta attributes as a RegionMeta
outer_radius	The outer radius as a astropy.units.Quantity angle.
visual	The visual attributes as a RegionVisual.

Methods Summary

discretize_boundary([n_points])	Discretize the boundary into a PolygonSphericalSkyRegion, as an approximation where all sides follow great circles.
to_pixel([wcs, ...])	Convert to a planar PixelRegion instance.
to_sky([wcs, include_boundary_distortions, ...])	Convert to a planar SkyRegion instance.
transform_to(frame[, merge_attributes])	Transform the SphericalSkyRegion instance into another instance with a different coordinate reference frame.

Attributes Documentation

center

The center position as a astropy.coordinates.SkyCoord.

inner_radius

The inner radius as a astropy.units.Quantity angle.

meta

The meta attributes as a RegionMeta

outer_radius

The outer radius as a astropy.units.Quantity angle.

visual

The visual attributes as a RegionVisual.

Methods Documentation

discretize_boundary(n_points=100)

Discretize the boundary into a PolygonSphericalSkyRegion, as an approximation where all sides follow great circles.

Parameters:

n_pointsint, optional

Number of points along the region’s boundary.

Returns:

poly_sky_region: PolygonSphericalSkyRegion

Spherical sky polygon object.

to_pixel(wcs=None, include_boundary_distortions=False, discretize_kwargs=None)

Convert to a planar PixelRegion 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 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.

discretize_kwargsdict, optional

Optional keyword arguments to pass to discretize_boundary() method if including boundary distortions.

Returns:

pixel_regionPixelRegion

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

to_sky(wcs=None, include_boundary_distortions=False, discretize_kwargs=None)

Convert to a planar SkyRegion 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 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.

discretize_kwargsdict, optional

Optional keyword arguments to pass to discretize_boundary() method if including boundary distortions.

Returns:

sky_regionSkyRegion

A planar 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).

transform_to(frame, merge_attributes=True)

Transform the SphericalSkyRegion instance into another instance with a different coordinate reference frame.

The precise frame transformed to depends on merge_attributes. If False, the destination frame is used exactly as passed in. But this is often not quite what one wants. E.g., suppose one wants to transform an ICRS coordinate that has an obstime attribute to FK4; in this case, one likely would want to use this information. Thus, the default for merge_attributes is True, in which the precedence is as follows: (1) explicitly set (i.e., non-default) values in the destination frame; (2) explicitly set values in the source; (3) default value in the destination frame.

Note that in either case, any explicitly set attributes on the source astropy.coordinates.SkyCoord that are not part of the destination frame’s definition are kept (stored on the resulting astropy.coordinates.SkyCoord), and thus one can round-trip (e.g., from FK4 to ICRS to FK4 without losing obstime).

Parameters:

framestr, or BaseCoordinateFrame class or instance

The frame to transform this coordinate into.

merge_attributesbool, optional

Whether the default attributes in the destination frame are allowed to be overridden by explicitly set attributes in the source (see note above; default: True).

Returns:

sph_sky_regionSphericalSkyRegion

A new spherical sky region represented in the frame frame.