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Last modified: 18 May 2010

URL: http://cxc-newtest.cfa.harvard.edu/ciao4.2/bugs/dmcoords.html

Bugs: dmcoords


Caveats

  1. dmcoords does not work correctly on the ACIS blank-sky background files (28 Jan 2010)

Bugs

  1. Incorrect azimuth and off-axis angle for HRC event files

  2. Using "op=cel celfmt=deg" gives incorrect results (28 Dec 2009)


Caveats

  1. dmcoords does not work correctly on the ACIS blank-sky background files (28 Jan 2010)

    The pointing (PNT) header keyword values in the background files are set to zero:

    unix% dmlist bgevt2_c7.fits header |grep PNT
    0058 RA_PNT                                  0           Real8        Pointing RA
    0059 DEC_PNT                                 0           Real8        Pointing Dec
    0060 ROLL_PNT                                0 [deg]     Real8        Roll (fake)
    

    These values indicate where the optical axis was during the observation. Having zero-values will cause the CIAO tool dmcoords to produce incorrect results when run with the background file.

    Workaround:

    Follow the workaround in the The ACIS "Blank-Sky" Background Files thread (S-Lang or Python) to update the PNT header keyword values.


Bugs

  1. Incorrect azimuth and off-axis angle for HRC event files

    A keyword was dropped when filtering columns from HRC evt2 files in the pre-CIAO 3.0 data model. This causes dmcoords to not have correct knowledge of the aspect solution; the tool therefore computes an incorrect zero point for the azimuth (phi) and off-axis angle (theta).

    Workaround:

    Use dmstat to get the DETX,DETY values:

    unix% dmstat "evt2[sky=region(reg)][cols det]"
    

    and then use dmcoords to convert these to theta and phi values.

  2. Using "op=cel celfmt=deg" gives incorrect results (28 Dec 2009)

    The results will be clearly incorrect, e.g.

    unix% dmcoords evt2.fits op=cel celfmt=deg ra=179.316235351 dec=-60.6187044
    % pget dmcoords x y
    -28175.51334419422
    1883.330449415633 
    

    Workaround:

    The results are correct if "celfmt=hms" is used instead.


Last modified: 18 May 2010