# SkyEllipticalAnnulus¶

class photutils.aperture.SkyEllipticalAnnulus(positions, a_in, a_out, b_out, b_in=None, theta=<Quantity 0. deg>)[source]

Bases: SkyAperture

An elliptical 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.

a_inscalar Quantity

The inner semimajor axis in angular units.

a_outscalar Quantity

The outer semimajor axis in angular units.

b_outscalar Quantity

The outer semiminor axis in angular units.

b_inNone or scalar Quantity

The inner semiminor axis in angular units. If None, then the inner semiminor axis is calculated as:

$b_{in} = b_{out} \left(\frac{a_{in}}{a_{out}}\right)$
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 SkyEllipticalAnnulus
>>> positions = SkyCoord(ra=[10.0, 20.0], dec=[30.0, 40.0], unit='deg')
>>> aper = SkyEllipticalAnnulus(positions, 0.5*u.arcsec, 2.0*u.arcsec,
...                             1.0*u.arcsec)


Attributes Summary

 a_in The inner semimajor axis in angular units. a_out The outer semimajor axis in angular units. b_in The inner semiminor axis in angular units. b_out The outer 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

 Make an independent (deep) copy. to_pixel(wcs) Convert the aperture to an EllipticalAnnulus object defined in pixel coordinates.

Attributes Documentation

a_in

The inner semimajor axis in angular units.

a_out

The outer semimajor axis in angular units.

b_in

The inner semiminor axis in angular units.

b_out

The outer 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 an independent (deep) copy.

to_pixel(wcs)[source]

Convert the aperture to an EllipticalAnnulus 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

An EllipticalAnnulus object.