SkyRectangularAnnulus#

class photutils.aperture.SkyRectangularAnnulus(positions, w_in, w_out, h_out, h_in=None, theta=<Quantity 0. deg>)[source]#

Bases: SkyAperture

A rectangular 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.

w_inscalar Quantity

The inner full width of the rectangular annulus in angular units. For theta=0 the width side is along the North-South axis.

w_outscalar Quantity

The outer full width of the rectangular annulus in angular units. For theta=0 the width side is along the North-South axis.

h_outscalar Quantity

The outer full height of the rectangular annulus in angular units.

h_inNone or scalar Quantity

The inner full height of the rectangular annulus in angular units. If None, then the inner full height is calculated as:

\[h_{in} = h_{out} \left(\frac{w_{in}}{w_{out}}\right)\]

For theta=0 the height side is along the East-West axis.

thetascalar Quantity, optional

The position angle (in angular units) of the rectangle “width” side. 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 SkyRectangularAnnulus
>>> positions = SkyCoord(ra=[10.0, 20.0], dec=[30.0, 40.0], unit='deg')
>>> aper = SkyRectangularAnnulus(positions, 3.0*u.arcsec, 8.0*u.arcsec,
...                              5.0*u.arcsec)

Attributes Summary

`h_in`	The inner full height in angular units.
`h_out`	The outer full height 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 rectangle "width" side.
`w_in`	The inner full width in angular units.
`w_out`	The outer full width in angular units.

Methods Summary

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

Attributes Documentation

h_in#: The inner full height in angular units.

h_out#: The outer full height 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 rectangle “width” side.

w_in#: The inner full width in angular units.

w_out#: The outer full width in angular units.

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 RectangularAnnulus 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:

apertureRectangularAnnulus object: A RectangularAnnulus 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.