Jcdua3f4q_flc.fits jcdua3f4q_sci1_exclude.reg None A more complete description of the 'exclusions' file can be found in the Notes section of the TweakReg task.įor our particular example we create a file 'exclusions.txt' with the following two lines: Also, if we do not want to use region files with the *last* extensions then we do not even need to use 'None' with those extensions. When we do not want to provide a DS9 region file for some images and/or extensions, 'None' (without apostrophes) can be entered instead of the DS9 region file name. This file must list region files for ALL input images and ALL 'SCI' extensions in these files. This can be achieved by providing TweakReg an exclusion file (through the 'exclusions' parameter). Let's assume that we want to exclude some regions of the SCI,1 extension of the 'jcdua3f4q_flc.fits' file from being used for sources finding. Using region files to exclude detected sources NOTE: all region files must comply with the DS9 region file format and all the regions must be provided in *image* coordinates. In *addition* to the old interpretation of regions as "exclude" regions, TweakReg now allows the use of both "include" and "exclude" regions (a property of regions in DS9) that can be used to tell TweakReg to find sources only within the "include" regions or not to find sources in the "exclude" regions (or a combination of the two). The new version (Drizzlepac 2.0) allows the following additional DS9 regions: circle, ellipse, polygon, and box. In the previous version of TweakReg, only circular regions could be used and these regions were treated as "exclude" regions, that is, sources inside these regions were excluded from the source list. Below we will show how to use TweakReg include/exclude DS9 regions. The include/exclude DS9 regions can be used to tell TweakReg to look for sources only in specific parts of the image, or to exclude some parts of the image from sources finding without using very restrictive parameters for source finding. to reduce the number of false detections even further, however, if these parameters are too restrictive, this may lead to some "good" sources not being found. We can still adjust detection threshold, use roundness/sharpness parameters, etc. However, there are still many sources detected either as cosmic rays or located inside extended galaxies (which could affect the accuracy of positions of these sources). These sources are shown as green dots in Figure 1. This has reduced the number of sources detected in 'jcdua3f4q_flc.fits' by almost a third to 5305 (from 13758). Updatehdr=False) Figure 1: Sources found by TweakReg in 'jcdua3f4q_flc.fits' (red points) *without* excluding "bad" pixels using DQ information and sources (green points) found in the same image *with* bad pixel "filtering" based on the DQ. Imagefindcfg=dict(threshold=50,conv_width=4.5,dqbits=0),\ In order to do this, we set the TweakReg parameter 'qdbits' within 'imagefindpars' to 0: We can reduce the number of cosmic rays detected as sources by enabling TweakReg to use DQ flags associated with image pixels. TweakReg found 13758 sources in the SCI,1 extension alone in the 'jcdua3f4q_flc.fits' image. The red points show the sources found by TweakReg when run with the above command. In Figure 1 we show a part of the 'SCI,1' image of the FITS file 'jcdua3f4q_flc.fits'. Imagefindcfg=dict(threshold=50,conv_width=4.5),\ With almost default parameters, TweakReg will find plenty of sources with most of them being either cosmic rays, extended sources, or point-like sources located inside large extended sources. We provide the ACS/WFC FLC files so that the user can re-create our results. This example is based on observations of 'MACSJ1149.5+2223-HFFPAR' (proposal ID: 13504, files 'jcdua3f4q_flc.fits' and 'jcdua3f8q_flc.fits'). In this example we show how to use DS9 regions with TweakReg in order to exclude spurious detections and parts of the input images that might trouble a proper identification of sources for alignment.
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