SkyEllipticalAperture#

class photutils.aperture.SkyEllipticalAperture(positions, a, b, theta=<Quantity 0. deg>)[source]#

Bases: SkyAperture

An elliptical 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.
ascalar Quantity: The semimajor axis of the ellipse in angular units.
bscalar Quantity: The semiminor axis of the ellipse in angular units.
thetascalar Quantity, optional: The position angle (in angular units) of the ellipse semimajor axis. For a right-handed world coordinate system, the position angle increases counterclockwise from North (PA=0).

Examples

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

Attributes Summary

`a`	The semimajor axis in angular units.
`b`	The semiminor axis in angular units.
`isscalar`	Whether the instance is scalar (i.e., a single position).
`positions`	The center position(s) in sky coordinates.
`shape`	The shape of the instance.
`theta`	The position angle in angular units of the ellipse semimajor axis.

Methods Summary

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

Attributes Documentation

a#: The semimajor axis in angular units.

b#: The semiminor axis in angular units.

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

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

shape#: The shape of the instance.

theta#: The position angle in angular units of the ellipse semimajor axis.

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 an EllipticalAperture 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:

apertureEllipticalAperture object: An EllipticalAperture object.

Notes

The aperture shape parameters are converted using the local WCS properties (pixel scale, rotation angle) 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.