daofind#

astropop.photometry.daofind(data, threshold, background, noise, fwhm, mask=None, sharp_limit=(0.2, 1.0), round_limit=(-1.0, 1.0), exclude_border=True, positions=None)#

Find sources using DAOfind algorithm.

Parameters:
data: array_like

2D array containing the image to extract the sources.

threshold: `int` or `float`

Minumim number of standard deviations above the background level where the algorithm will start to consider the sources.

background: `float` or `~numpy.ndarray`

Background level estimation. Can be a single global value, or a 2D array with by-pixel values.

noise: `float` or `~numpy.ndarray`

RMS or any other noise estimation to use in the detection. Can be a single global value, or a 2D array with by-pixel values. Due to limitations of photutils, if a 2D array is provided, it will be converted to a scalar using the median.

fwhm: `float`

Full width at half maximum: to be used in the convolve filter.

sharp_limit: array_like or `None` (optional)

Low and high cutoff for the sharpness statistic. None will disable the sharpness filtering. Default: (0.2, 1.0)

round_limitarray_like or None (optional)

Low and high cutoff for the roundness statistic. None will disable the roundness filtering. Default: (-1.0,1.0)

mask: array_like (optional)

Boolean mask where 1 pixels are masked out in the background calculation. Default: None

exclude_border: `bool` (optional)

If True, sources found within half the size of the convolution kernel from the image borders are excluded. Default: True

positions: array_like (optional)

List of (x, y) positions where to look for sources. If provided, the source finding step will be ignored and the centroids will be refined and filtered. Default: None

Returns:
sources: astropy.table.Table

Table with the sources found. The table will contain the following columns: - id: source ID - x, y: x and y coordinates of the source centroid - xcentroid, ycentroid: same as x and y - peak: value of the source peak - flux: integrated (background-subtracted) source flux within the

segment

  • fwhm: FWHM of circular gaussian fit of the source

  • sharpness: The source DAOFIND sharpness statistic.

  • roundness: The source DAOFIND roundness statistic. Maximum between g_roundness and r_roundness.

  • g_roundness: The DAOFIND roundness statistic based on Gaussian marginal fit. Good for assymetries aligned with the x or y axis.

  • s_roundness: The DAOFIND roundness statistic based on symmetry of the source. Good for assymetries aligned with the diagonal.

  • sigma_x, sigma_y: standard deviation of the source elipsoid along x and y

  • theta: rotation angle of the source elipsoid (degrees) from the positive x axis

  • fwhm: FWHM of circular gaussian fit of the source

  • eccentricity: The eccentricity of the 2D Gaussian function that has the same second-order moments as the source.

  • elongation: The ratio of the lengths of the semimajor and semiminor axes.

  • ellipticity: 1.0 minus the elongation.

  • cxx, cyy, cxy: SourceExtractor ellipse parameters. See [SourceExtractor docs]_

  • area: area of the segment, in pixels