How can I use my DS9 preference file through Sherpa's image_* routines?  

In order to avoid possible conflicts between multiple DS9 sessions the Sherpa image_* routines initializes DS9 in a manner where previously defined preferences saved to a DS9 preference file is not loaded into the session. For Sherpa to utilize the DS9 preferences, create a sub-directory, .sherpa, in your home directory and link the DS9 preference file to one prefixed with "sherpa". For example using the DS9 v8.7 preference file:

unix% ln -s ${HOME}/.ds9/ds9.8.7.prf ${HOME}/.sherpa/sherpa.8.7.prf