This is archive contains an incomplete beta-version of SExtractor 1.2. It has been released for test purposes, and should therefore be used with extreme caution! This beta will probably the penultimate one before final release. New features include: - support for WCS coordinates. This means that you can get the alpha and delta for objects detected on FITS images which comply with the WCS standard (see http://www.cv.nrao.edu/fits/documents/wcs/wcs.html). The astrometric mapping relies on Mark Calabretta's WCS library (V2.4 in C). SExtractor also handles precession in the FK5 system, as well as transformations from J2000 (FK5) to B1950 (FK4) coordinates. Shape parameters are transformed through a local, linear approximation of the astrometric mapping. I am not an astrometrist, I would therefore appreciate some feedback concerning these features. All informations concerning precession in the FK4 system are welcome, as SExtractor does only precess in the FK4 system presently. I would also gladly add support for DSS images if someone can provide me with a decent description of their astrometric parameters! - 2D positional error estimate through ERRA_xxx, ERRB_xxx and ERRTHETA_xxx. Note: these estimates are exact for unconvolved, white-noised images only. - Linear photometric parameters (FLUX_xxx and FLUXERR_xxx in addition to MAG_xxx and MAGER_xxx). - Better outputs: units and vectors in FITS, (limited) backward compatibility with the old V1.0 output format (CATALOG_TYPE FITS_1.0), new detailed ASCII output mode (CATALOG_TYPE ASCII_HEAD). - Handling of gigantic images (up to 2e9x2e9 pixels on 64bit machines). - Online decompression of compressed DeNIS images. - New "vignet" vector output: for instance VIGNET(8,5) in the .param file will write in the output catalog a small 8x5 pixels array around each detection center. - Many bugs corrected, among which: crash in the background mapping on very large images and incorrect S/G separation in blended objets. The documentation is currently being written. In the meanwhile you may consult the param.h file in the source/ directory for a minimum description of each parameter. /*- Previous notes for V1.2b5 (Jan 1997) */ Note that the CLASS_STAR, FWHM_IMAGE an FWHM_WORLD parameters haven't be tested in this version (they shall be replaced by better estimators in future versions). Many algorithms have been changed in this version. Therefore it is expected that most measurements should yield results (slightly) different than those obtained with earlier versions. In general accuracy and detection performances should have increased, especially at low S/N; however I would appreciate to have feedback from people involved in weak-lensing studies or astrometrical work for instance concerning the accuracy of X,Y,A,B and THETA parameters, which are now computed on FILTERED images. The FITS catalog output format is yet in a temporary state; it is recommended not to use it. The documentation has not been updated yet; the following lines describe changes made to the configuration files. In the "config/" sub-directory you will find some configuration files. They are basically the same as in the previous version except that: - in the *.conv files: There is now a "NORM" keyword next to the "CONV" keyword. It just says that the convolution mask must be normalized ("NONORM" for no normalization). In previous versions this feature was controlled through the "CONVOLVE_NORM" keyword in the .sex file. However, old *.conv files are still accepted by the new version, and are automatically normalized, while a warning message is printed. - in the default.sex file: many things have changed. *There is now a new "DETECT_IMAGE" parameter which requires a string as argument. If it set to "SAME", it means that the input image will be used for both detection and measurement, as in the old version. If you give it an image filename (provided that the dimensions of this image are the same as those of the input image), it will be used as a kind of ``detection template'': all sources will be detected and deblended on this image, and will serve as reference for the measurements done on the regular image. *The EXTRACT_MINAREA keyword has become DETECT_MINAREA (for aesthetic reasons), but keeps exactly the same function. Idem for CONVOLVE -> FILTER and CONVOLVE_NAME -> FILTER_NAME. *The old THRESHOLD parameter has been now split in two: DETECT_THRESH and ANALYSIS_THRESH. DETECT_THRESH is the threshold of detection, just as before. You may express it in units of sigma of the background noise, or in surface brightness units, associated to a magnitude Zero-Point of the detection frame. Ex: "DETECT_THRESH 3.0" will set the threshold at 3.0 sigma, "DETECT_THRESH 22.0,25.4" will set the threshold at 22 mag.arcsec-2 for a detection-image whose mag-ZP is 25.4 mag. (note: the "PIXEL_SCALE" should have been set to the right value). In this way, the THRESHOLD_TYPE parameter has been eliminated. ANALYSIS_THRESH is a threshold in the measurement-frame (it can be the same as the detection-frame). It is used only for estimators that need accurate informations about the object profile in the measurement frame: star/galaxy separation and FWHM. If you don't know what to do with it, just leave it to 3.0 (sigmas, you may also express it in mag.arcsec-2 like for DETECT_THRESH, but in this case the mag-ZP will refer to the measurement image). *BACK_XSIZE and BACK_YSIZE have been replaced by a single keyword, BACK_SIZE, which can accept up to 2 parameters (width and height of the background meshes). If only one number is given, width and height are simultaneously set to this value (useful because most of the time, people use square meshes!). The same happens for the BACK_FLTRXSIZE and BACK_FLTRYSIZE which have become BACK_FILTERSIZE. Similarly, the 3 Kron parameters PHOTOM_K... have been replaced by a common PHOT_AUTOPARAMS which requires 2 arguments, equivalent resp. to the former PHOTOM_KPAR and PHOTOM_KMINSIG. PHOTOM_KSIG is now set definitely to 6.0 in the code. This is because the new MAG_AUTO apertures are much more robust to crowding effects than before. Also, for aesthetic reasons, PHOTOM_APERTURE has become PHOT_APERTURES. There is an S at ApertureS, because the software can now photometer each source simultaneously through up to 4 apertures (see default.param). In default.param, MAG_APER is equivalent to MAG_APER1, and MAGERR_APER is equivalent to MAGERR_APER1. *CHECKIMAGE_TYPE now accepts a new type: MINIBACKGROUND. It produces in output a FITS image in which each physical pixel corresponds to one background mesh. This image is therefore roughly BACK_SIZE smaller than the input frame. The CONVOLVED option is now called FILTERED. - The MAG_AUTO magnitudes are computed in a slightly different way than before, leading to a gain of about 20% in photometric precision in most extragalactic fields, especially in clusters. Obviously MAG_BEST benefits from this. - The CLEAN_PARAM efficiency has increased, compared to previous versions. Smaller values (around 1.0) should now be used. Please report all bugs to bertin@iap.fr. Thanks! Emmanuel Bertin.