improve.rst

Command Line Commands

Here we have a directory called "miri_example" that has some MIRI cals. JHAT can also be run from the command line in the following way:

run_st_wcs_align.py miri_example/jw02666001001_02101_00001_mirimage_cal.fits --outrootdir '.'
        --outsubdir aligned  --overwr -v --refcat gaia --saveplots -tt -pp --histocut_order dxdy

Which produces the following plots:

Improving Alignment

Sometimes, in particular if there are not enough sources or the images are particularly poorly aligned, JHAT has a difficult time finding a good alignment (or it can be improved). Here are a few methods for improving the results. First we add cuts on sharpness, roundness, and brightness:

run_st_wcs_align.py miri_example/jw02666001001_02101_00001_mirimage_cal.fits --outrootdir '.'
        --outsubdir aligned  --overwr -v --refcat gaia --saveplots -tt -pp --histocut_order dxdy
        --roundness1_lim -0.5 0.5 --objmag_lim 14 21.5 --sharpness_lim 0.6 0.85 --refmag_lim 16 25

Next we increase the allowed distance between matches between the reference and target catalogs (d2d_max), and limit the difference between measured magnitudes between the catalogs.

run_st_wcs_align.py miri_example/jw02666001001_02101_00001_mirimage_cal.fits --outrootdir '.'
        --outsubdir aligned  --overwr -v --refcat gaia --saveplots -tt -pp --histocut_order dxdy
        --roundness1_lim -0.5 0.5 --objmag_lim 14 21.5 --refmag_lim 16 25 --delta_mag_lim -2 2 --d2d_max 1.5

Finally, we might use the previous results to guess the rough needed offset, and apply it directly before the matching begins:

run_st_wcs_align.py miri_example/jw02666001001_02101_00001_mirimage_cal.fits --outrootdir '.'
        --outsubdir aligned  --overwr -v --refcat gaia --saveplots -tt -pp --histocut_order dxdy
        --roundness1_lim -0.5 0.5 --objmag_lim 14 21.5 --refmag_lim 16 25 --delta_mag_lim -2 2
        --d2d_max 1.5 --xshift 3 --yshift -4