# EllipticalAperture¶

class `photutils.aperture.``EllipticalAperture`(positions, a, b, theta=0.0)[source]

An elliptical aperture defined in pixel coordinates.

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

Parameters
positionsarray_like or `Quantity`

The pixel coordinates of the aperture center(s) in one of the following formats:

afloat

The semimajor axis of the ellipse in pixels.

bfloat

The semiminor axis of the ellipse in pixels.

thetafloat, optional

The rotation angle in radians of the ellipse semimajor axis from the positive `x` axis. The rotation angle increases counterclockwise. The default is 0.

Raises
ValueError`ValueError`

If either axis (`a` or `b`) is negative.

Examples

```>>> from photutils.aperture import EllipticalAperture
>>> aper = EllipticalAperture([10., 20.], 5., 3.)
>>> aper = EllipticalAperture((10., 20.), 5., 3., theta=np.pi)
```
```>>> pos1 = (10., 20.)  # (x, y)
>>> pos2 = (30., 40.)
>>> pos3 = (50., 60.)
>>> aper = EllipticalAperture([pos1, pos2, pos3], 5., 3.)
>>> aper = EllipticalAperture((pos1, pos2, pos3), 5., 3., theta=np.pi)
```

Attributes Summary

 `a` Check that value is a strictly positive (> 0) scalar. `area` Return the exact area of the aperture shape. `b` Check that value is a strictly positive (> 0) scalar. `positions` Validate and set positions for pixel-based apertures. `theta` Check that value is a scalar.

Methods Summary

 `to_sky`(wcs) Convert the aperture to a `SkyEllipticalAperture` object defined in celestial coordinates.

Attributes Documentation

`a`

Check that value is a strictly positive (> 0) scalar.

`area`
`b`

Check that value is a strictly positive (> 0) scalar.

`positions`

Validate and set positions for pixel-based apertures.

In all cases, pixel positions are converted to a 2D `ndarray` (without units).

`theta`

Check that value is a scalar.

Methods Documentation

`to_sky`(wcs)[source]

Convert the aperture to a `SkyEllipticalAperture` object defined in celestial 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 `SkyEllipticalAperture` object.