# SkyCircularAnnulus¶

class photutils.aperture.SkyCircularAnnulus(positions, r_in, r_out)[source]

A circular annulus aperture defined in sky coordinates.

The aperture has a single fixed size/shape, but it can have multiple positions (see the positions input).

Parameters
positionsSkyCoord

The celestial coordinates of the aperture center(s). This can be either scalar coordinates or an array of coordinates.

r_inscalar Quantity

The inner radius of the circular annulus, either in angular or pixel units.

r_outscalar Quantity

The outer radius of the circular annulus, either in angular or pixel units.

Examples

>>> from astropy.coordinates import SkyCoord
>>> import astropy.units as u
>>> from photutils import SkyCircularAnnulus
>>> positions = SkyCoord(ra=[10., 20.], dec=[30., 40.], unit='deg')
>>> aper = SkyCircularAnnulus(positions, 0.5*u.arcsec, 1.0*u.arcsec)


Attributes Summary

 positions Check that value is a SkyCoord. r_in Check that value is either an angular or a pixel scalar Quantity. r_out Check that value is either an angular or a pixel scalar Quantity.

Methods Summary

 to_pixel(wcs) Convert the aperture to a CircularAnnulus object defined in pixel coordinates.

Attributes Documentation

positions

Check that value is a SkyCoord.

r_in

Check that value is either an angular or a pixel scalar Quantity.

r_out

Check that value is either an angular or a pixel scalar Quantity.

Methods Documentation

to_pixel(wcs)[source]

Convert the aperture to a CircularAnnulus object defined in pixel coordinates.

Parameters
wcsWCS object

A world coordinate system (WCS) transformation that supports the astropy shared interface for WCS (e.g., astropy.wcs.WCS, gwcs.wcs.WCS).

Returns
aperture

A CircularAnnulus object.