LuneSphericalSkyRegion

class regions.LuneSphericalSkyRegion(center_gc1, center_gc2, meta=None, visual=None)

Bases: SphericalSkyRegion

Class for a spherical “lune”, the intersection between to great circles in spherical geometry.

Composed of two CircleSphericalSkyRegions.

Parameters:

center_gc1SkyCoord

The center position of the first great circle.

center_gc2SkyCoord

The center position of the second great circle.

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

bounding_circle	Bounding circle for the spherical sky region.
bounding_lonlat	Bounding longitude and latitude of the spherical sky region, in the region's frame.
center_gc1	The center position of the first great circle as a astropy.coordinates.SkyCoord.
center_gc2	The center position of the second great circle as a astropy.coordinates.SkyCoord.
centroid	Region centroid.
frame	Coordinate frame of the region.
meta	The meta attributes as a RegionMeta
vertices	Region vertices.
visual	The visual attributes as a RegionVisual.

Methods Summary

contains(coord)	Check whether a sky coordinate falls inside the spherical sky region.
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

bounding_circle

bounding_lonlat

center_gc1

The center position of the first great circle as a astropy.coordinates.SkyCoord.

center_gc2

The center position of the second great circle as a astropy.coordinates.SkyCoord.

centroid

Region centroid.

frame

meta

The meta attributes as a RegionMeta

vertices

Region vertices.

For a lune, these are the intersections of the two bounding great circles, and are antipodes.

visual

The visual attributes as a RegionVisual.

Methods Documentation

contains(coord)

Check whether a sky coordinate falls inside the spherical sky region.

Parameters:

coordSkyCoord

The position or positions to check.

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.