Using SExtractor to find stars in FITS images
[x pixel center] [y pixel center] [instrument magnitude]
CATALOG_NAME image.sex # name of the output catalog CATALOG_TYPE ASCII_HEAD # "ASCII_HEAD","ASCII","FITS_1.0" or "FITS_LDAC" PARAMETERS_NAME daofind.param # name of the file containing catalog contentsOther parameters for photometry or background may be modified as necessary.
Then set the parameters you need to emulate the daofind output format in the file daofind.param, which contains simply
X_IMAGE Y_IMAGE MAG_BESTThe default.nnw and default.conv files do not need to be changed.
$ sex -c daofind.sex test.fits Frame: "16139p3131R" / 1024 x 1024 / 16 bits INTEGER data Background: -0.17547 RMS: 9.83951 / Threshold: 14.7593 Objects: detected 504 / sextracted 503 > All done $ sort -n +2.0 image.sex | head -100 > test.sexThen run imwcs as in the example:
$ imwcs -vd test.sex -c uac -h 50 test.fitsA shell script, imsex, which requires the file default.sex, has been written to run SExtractor without having to establish local parameter files. It can also automatically extract image extensions from multi-extension FITS files before running SExtractor on them. Returned stars are sorted from brightest to faintest, and the brightest 100 are written to a file named as the input file, with .sex instead of the input .fits (or whatever). If an image extension is extracted, the output files (FITS and DAO-format) have .extension name inserted before the suffix. For example, if the file multitest.fits has four image extensions with EXTNAME set in each one,
imsex -m -n 200creates the image files multitest_IM1.fits, multitest_IM2.fits, multitest_IM3.fits, and multitest_IM4.fits, and the SExtracor output files multitest_IM1.sex, multitest_IM2.sex, multitest_IM3.sex, and multitest_IM4.sex, with up to 200 stars each. As with all WCSTools programs, typing imsex with no arguments lists the possible arguments.