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Last modified: 12 December 2019

URL: https://cxc.cfa.harvard.edu/sherpa/watchout.html

Sherpa "Watch Out" Page

This page lists noteworthy items and issues about the Sherpa 4.12 release. For the full list of known issues please review the:


Running Sherpa

Sherpa ploting is done with Matplotlib and ChIPS is no-longer provided with CIAO 4.12

CIAO 4.11 was the last release to include the ChIPS plotting system. Sherpa in CIAO 4.12 will now automatically switch to use matplotlib if your $HOME/.sherpa.rc is still set to use chips, but you will see the following warning (shown in bold text below):

unix% sherpa
-----------------------------------------------------
Welcome to Sherpa: CXC's Modeling and Fitting Package
-----------------------------------------------------
Sherpa 4.12.0

Python 3.7.5 (default, Oct 25 2019, 15:51:11) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.9.0 -- An enhanced Interactive Python. Type '?' for help.

IPython profile: sherpa
Using matplotlib backend: Qt5Agg
WARNING: chips is not supported in CIAO 4.12+, falling back to matplotlib.
WARNING: Please consider updating your $HOME/.sherpa.rc file to suppress this warning.

To stop this warning, edit $HOME/.sherpa.rc so that the plot_pkg line reads:

plot_pkg : pylab
IPython Packaged with CIAO OTS

CIAO includes IPython in the CIAO OTS directory which is used by Sherpa and ChIPS to provide command-line user interfaces. These programs create an IPython profile in the directory $HOME/.ipython-ciao.

If IPython users want any personal customizations to be available when running CIAO, they will have to copy them from $HOME/.ipython to $HOME/.ipython-ciao.

User Python modules must not have the same name as CIAO/Sherpa modules.

When loading a module in Python, Python first looks in the current working directory for this module, then in the directories listed in the PYTHONPATH environment variable. Therefore, if you have a script named 'sherpa.py' in your current working directory, for example, Sherpa will fail to load because the script ./sherpa.py is loaded, not the Sherpa code. Please ensure that the names of your Python scripts do not exactly match those of Python modules packaged with CIAO.


Data Caveats

Spectral analyses of ACIS data with a limited pulse-height range

Before fitting ACIS data sets with restricted pulse-height ranges, please read the CIAO caveat "Spectral analyses of ACIS data with a limited pulse-height range."

A complete list of caveats for Chandra data is available on the CIAO Data Caveats webpage.