class astropy.visualization.wcsaxes.SphericalCircle(center, radius, resolution=100, vertex_unit=Unit('deg'), **kwargs)[source]

Bases: matplotlib.patches.Polygon

Create a patch representing a spherical circle - that is, a circle that is formed of all the points that are within a certain angle of the central coordinates on a sphere. Here we assume that latitude goes from -90 to +90

This class is needed in cases where the user wants to add a circular patch to a celestial image, since otherwise the circle will be distorted, because a fixed interval in longitude corresponds to a different angle on the sky depending on the latitude.

centertuple or Quantity

This can be either a tuple of two Quantity objects, or a single Quantity array with two elements.


The radius of the circle

resolutionint, optional

The number of points that make up the circle - increase this to get a smoother circle.


The units in which the resulting polygon should be defined - this should match the unit that the transformation (e.g. the WCS transformation) expects as input.


Additional keyword arguments are passed to Polygon

xy is a numpy array with shape Nx2.

If closed is True, the polygon will be closed so the starting and ending points are the same.

Valid keyword arguments are:


agg_filter: a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array alpha: float or None animated: bool antialiased or aa: unknown capstyle: {‘butt’, ‘round’, ‘projecting’} clip_box: Bbox clip_on: bool clip_path: Patch or (Path, Transform) or None color: color contains: unknown edgecolor or ec: color or None or ‘auto’ facecolor or fc: color or None figure: Figure fill: bool gid: str hatch: {‘/’, ‘\’, ‘|’, ‘-‘, ‘+’, ‘x’, ‘o’, ‘O’, ‘.’, ‘*’} in_layout: bool joinstyle: {‘miter’, ‘round’, ‘bevel’} label: object linestyle or ls: {‘-‘, ‘–’, ‘-.’, ‘:’, ‘’, (offset, on-off-seq), …} linewidth or lw: float or None path_effects: AbstractPathEffect picker: None or bool or callable rasterized: bool or None sketch_params: (scale: float, length: float, randomness: float) snap: bool or None transform: Transform url: str visible: bool zorder: float