fistar - detecting and characterizing point-like sources
fistar [options] <input>
[-o|--output <output>]
The main purpose of this program is to detect and extract sources
(i.e. star-like objects) from astronomical images. The source detection and
extraction are based on three major steps. First, pixel groups are derived
which are possibly belong to the sources (these preliminary detections are
callad source "candidates"). Second, these candidates are modelled
with some sort of analytic model funcion, in order to derive more precise
centroid coordinates and shape parameters. The last step is to extract the
point-spread function (PSF) for the image, based on the detected and
modelled sources. Basically, the input for this program must be an
astronomical image while the output is the list of detected and extracted
sources and their respective characteristics.
- -t, --threshold
<threshold>
- Detection peak threshold, in ADUs.
- -f, --flux-threshold
<flux threshold>
- Detection flux threshold, in ADUs.
- --algorithm
<algorithm>
- Source cadidate extraction algorithm. It can be "uplink"
(default) or "parabolapeak".
- -p, --prominence
<prominence>
- Critical relative prominence parameter used in the "uplink"
algorithm. The default is to use no prominence based pixel grouping.
- -r, --shrink
<shrink factor>
- Shrink factor applied before star candidate detection. The image is shrunk
by this specific factor and after the detection, the candidate coordinates
are multiplied by this value.
- --only-candidates
- Do not involve any analitic model funcion during the derivation of the
centroid coordinates and shape parameters, but derive these from some sort
of simple pixel statistics.
- --model
<model>[order=<order>]
- Analytic model function used in the second stage of source extraction.
This can be "gauss" (symmetic Gaussian profile),
"elliptic" (assymetric Gaussian profile) and
"deviated" (Gaussian profile multiplied by a polynomial up to
the specified order).
- --iterations
symmetric=<n>,general=<n>
- The number of Levenberg-Marquardt iterations during the analytic model
fit. The fit is done in two substeps, first the symmetric profile
parameters are derived only, which step is followed by the fit for all of
the shape parameters.
- -s, --sort
{x|y|peak|fwhm|amp|flux|noise|s/n}
- Sort the output list of extracted sources by X or Y coordinate, peak flux
(no background level subtracted), profile FWHM, peak intensity (background
level is subtracted), total flux, noise level or signal-to-noise ratio;
respectively.
- --mag-flux
<mag>,<flux>
- Magnitude - flux conversion level. The specified magnitude will be
equivalent to the specified flux level.
- -M, --input-mask
<image file>
- Input mask file to co-add to the mask of the input image. Useful for
marking pixels to be excluded from source extraction process beyond the
ones which are previously marked in the input image.
- -F, --format
<format>
- Comma separated list of format tags, for formatting the output list of
extracted sources. Each row represents an extracted source while the
format specified here defines the quantities listed in each row of the
output file. See "Format tags" for more details.
- id
- An unique identifier for the source (an integer number, in fact).
- ix
- Integer X coordinate for the centroid pixel
- iy
- Integer Y coordinate for the centroid pixel
- x
- Centroid X coordinate in native coordinate convention.
- y
- Centroid Y coordinate in native coordinate convention.
- bg
- Background level
- amp
- Peak amplitude
- S
- Gaussian momenum for the stellar profile (S=1/sigma^2)
- D
- plus-shaped momentum for the stellar profile
- K
- cross-shaped momentum for the stellar profile
- sigma
- sigma parameter for the stellar profile (FWHM is roughly 2.35 *
sigma)
- delta
- delta (plus-shaped deviance) parameter for the stellar profile
- kappa
- kappa (cross-shaped deviance) parameter for the stellar profile
- fwhm
- full width at half magnitude (FWHM) of the stellar profile
- ellip
- ellipticity of the stellar profile
- pa
- position angle of the stellar profile
- flux
- Total flux of the source
- nosie
- Noise level of the source
- s/n
- Signal-to-noise ratio of the detection
- magnitude
- Brightness of the source in magnitudes (see also --mag-flux)
- cx
- Candidate centroid X coordinate (derived from pixel flux statistics).
- cy
- Candidate centroid Y coordinate (derived from pixel flux statistics).
- cbg
- Background level for the source candidate
- camp
- Peak amplitude of the source candidate
- cmax
- Maximum intensity on the source cadidate
- cs
- Gaussian momenum for the source cadidate, derived from pixel flux
statistics
- cd
- plus-shaped momentum for the source cadidate, derived from pixel flux
statistics
- ck
- cross-shaped momentum for the source cadidate, derived from pixel flux
statistics
- npix
- number of pixels assigned to the detetcted source
- --psf
<parameters>
- Comma-separated list of parameters related to the PSF fitting:
- grid=<grid>
- subgrid size for the PSF
- halfsize=<half
size>
- half-size of the PSF stamp, the full size of the stamp will always be
2*<half size>+1 and the PSF itself is centered at the center of the
central pixel.
- order=<order>
- order of spatial variations in the PSF
- symmetrize
- symmetrize the resulting PSF (i.e. fit a symmetric PSF instead of a normal
one)
- spline
- use a spline interpolation during the determination of the PSF
- --output-psf
<output PSF FITS file>
- Name of the output file where the PSF is saved in FITS format. The PSF is
stored in a 3 dimensional (a.k.a. "data cube") structure where
the z-axis is for the various polynomial coefficients describing the
spatially varied PSF.
- -C, --input-cadidates
<cadidate list file>
- Name of input cadidate list file. If such a file is defined in the command
line, the cadidates are not searched by the build-in algorithms. Instead,
the centroids are read from this file and the pixels for each object are
defined within a certain radius from this centroid (see
-r|--cadidate-radius also). The role of this option is twofold.
First, it is suitable if only some of the sources have to be modelled with
an analytic function; second, PSF determination can be done only a
previously cleaned list of sources, in the case when there might be
contaminating sources too.
- -r,
--candidate-radius <radius>
- This option defines a distance, where pixels within this are assigned to
the candidate.
- --col-xy
<colx>,<coly>
- Column indices for X and Y centroid coordinates.
Report bugs to <apal@szofi.net>, see also
https://fitsh.net/.
Copyright © 1996, 2002, 2004-2008, 2010-2016, 2018-2020;
Pal, Andras <apal@szofi.net>