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Last modified: 17 July 2024

Frequently Asked Questions

Answers to common CIAO questions. For common warnings and error messages, refer to the bugs pages.



  1. How do I install CIAO?
  2. How do I upgrade CIAO?
  3. What is the conda package manager?
  4. Which should I choose to install CIAO: conda or ciao-install?
  5. What is a "standard" CIAO installation?
  6. How do I know what version of CIAO is installed?
  7. Which CALDB version is installed on my system?


  1. How do I stop Conda from changing the prompt?
  2. How do I get conda to install into a different directory (eg not my $HOME dir)?
  3. How do I remove old cached versions of packages?


  1. What Python version and packages are provided with CIAO 4.16?
  2. Can I use jupyter notebooks or install Python modules like Astropy, matplotlib, and Scipy with CIAO 4.16?

Data Products

  1. Why are the data files divided into primary and secondary directories?
  2. When was my observation performed?
    When was the file created?
    What version of data processing was used?
  3. What does the CREATOR header keyword mean?
  4. What is the sky range of each detector?
  5. What was the aimpoint of the observation?
  6. What is the difference between the RA and DEC NOM, TARG, and PNT header keywords?
  7. What is the focal plane temperature for my observation?
  8. Why are there sometimes multiple asol1.fits files for my observation?
    How do I treat these in my analysis?
  9. What is the CYCLE keyword?
    Should I be concerned if it's missing from my data?

Parameter Files

  1. Why does a tool not execute when I get the following error?
    pget: parameter not found...
    parammatch : can't find parameter PARAMNAME in reference list
    parameter error?
  2. Why should I delete my parameter files after upgrading CIAO?
  3. How do I run multiple instances of a CIAO tool without clobbering the parameter file?
  4. The tool is failing because ")sval" has somehow shown up in the parameter value.

Data Model

  1. How do I change the MEM option when I get this error?
    # DMCOPY (CIAO): WARNING: Creating large image: 999 MB. Current max set at 500 MB.
      Increase maximum using [opt mem=n] or increase blocking to reduce size.
  2. How can I define a region around a single chip?
  3. Why should I filter on sky coordinates rather than the CCD_ID column?
  4. How do I copy a block from one file to another?
  5. What does this Data Model error mean?
    # DMCOPY (CIAO): DM Parse error: cannot mix EXCLUDE and FILTER
  6. What happened to my FITS structural keywords?
  7. Why does using an exclude filter take so long?
  8. What does this warning mean?
    WARNING: Zero length polygon line segment at (x,y) (index = z)


  1. Why am I getting an ARDLIB error about a bad pixel file from a different ObsID?
    ***ARDLIB error: Unable to find data file acisf01842_000N002_bpix1.fits[BADPIX7]
  2. What does this ARDLIB warning mean?
    ***ARDLIB warning: Filename some_file.fits does not specify an extension. 
    Assuming the first "interesting" extension.
  3. How can I tell CIAO to use a different HRMA effective area file?

Computer Environment

  1. What is a shell?
    What shell am I using?


  1. What is the maximum size region file that CIAO can process?

User Interface


  1. Why can I only see a subsection of the event file? Where are the rest of the data?
  2. Can I use a newer version of ds9 than the one packaged with CIAO?
  3. How do I build polygon regions in ds9?
  4. How do I rotate a region in ds9?
  5. How do I display a source list on my data?



  1. Why hasn't the CALDBVER keyword been updated after I run this tool?
  2. Why is my level 2 event file larger than the one from the pipeline?


  1. How can I specify the datatype of the output image?


  1. How do I extract many spectra with one command?
  2. Why do I get a parse error with this region file?
    # Region file format: CIAO version 1.0	
  3. Why does dmextract convert arcseconds to arcminutes when I use pset?


  1. How can I make a mask from an exposure file?


  1. How can I calculate the centroid of counts in a region?


  1. Why is the column moved to the end of the table when I try to update it in place?


  1. What if the tg_create_mask extraction regions extend beyond the detector edge?


  1. Why do I get an error message that the size of the PSF image or Exposure map does not match the infile?
    # wrecon (CIAO): ERROR: psf image size (3874, 3988) does not match input image size (8192, 8192)