SkyCircularAnnulus#

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

Bases: SkyAperture

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 in angular units.
r_outscalar Quantity: The outer radius of the circular annulus in angular units.

Examples

>>> from astropy.coordinates import SkyCoord
>>> import astropy.units as u
>>> from photutils.aperture import SkyCircularAnnulus
>>> positions = SkyCoord(ra=[10.0, 20.0], dec=[30.0, 40.0], unit='deg')
>>> aper = SkyCircularAnnulus(positions, 0.5*u.arcsec, 1.0*u.arcsec)

Attributes Summary

`isscalar`	Whether the instance is scalar (i.e., a single position).
`positions`	The center position(s) in sky coordinates.
`r_in`	The inner radius in angular units.
`r_out`	The outer radius in angular units.
`shape`	The shape of the instance.

Methods Summary

`copy`()	Make a deep copy of this object.
`to_pixel`(wcs)	Convert the aperture to a `CircularAnnulus` object defined in pixel coordinates.

Attributes Documentation

isscalar#: Whether the instance is scalar (i.e., a single position).

positions#: The center position(s) in sky coordinates.

r_in#: The inner radius in angular units.

r_out#: The outer radius in angular units.

shape#: The shape of the instance.

Methods Documentation

copy()#

Make a deep copy of this object.

Returns:

resultAperture: A deep copy of the Aperture object.

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:

apertureCircularAnnulus object: A CircularAnnulus object.

Notes

The aperture shape parameters are converted using the local WCS pixel scale evaluated at the first aperture position. Because aperture objects require scalar shape parameters, only a single reference position is used for the conversion. For apertures with multiple positions used with a WCS that has spatially-varying distortions, this may produce inaccurate results for positions far from the first position.