An illustrative run of xselect on ACIS data.

First we read the data in... 
genji.gsfc.nasa.gov> xselect
 
                         **  XSELECT V2.0   **
 
 
 Notes: XSELECT set up for      ASCA
 Time keyword is TIME       in units of s
 Default timing binsize =   16.000
 
xsel:ASCA > read e
> Enter the Event file dir >[./] 
> Enter Event file list >[] screened.evt
Got new mission: AXAF
> Reset the mission ? >[yes] 
 
 Notes: XSELECT set up for      AXAF
 Time keyword is TIME       in units of s
 Default timing binsize =   16.000
 
 
Setting...
 Image  keywords   = X          Y           with binning =    4
 WMAP   keywords   = CHIPX      CHIPY       with binning =   32
 Energy keywords   = PHA                    with binning =    1
 
 
Getting Min and Max for Energy Column...
Got min and max for PHA:     0  36855
 
Could not get minimum time resolution of the data read
Number of files read in:            1
 
******************** Observation Catalogue ********************
 
Data Directory is: /local/genji/data3/kaa/SSA13/primary/
HK Directory is: /local/genji/data3/kaa/SSA13/primary/
 
 
        OBJECT      DATE-OBS    LIVETIME DETNAM      READMODE    FIRSTROW    NROWS
      1 S-Z CLUSTER 1999-12-03T 0.98E+05 ACIS-23678  TIMED       NOT_FOUND   NOT_FOUND
The DETNAM keyword indicates that chips 2,3,6,7, and 8 are active. These correspond to 3 spectroscopy and 2 imaging chips. To see the entire detector plane make an image with the default binning... 

xsel:AXAF-ACIS-FAINT > extr image
extractor v3.79  21 Jun 2000
 Getting FITS WCS Keywords
 Doing file: /local/genji/data3/kaa/SSA13/primary/screened.evt
100% completed
          Total      Good    Bad: Region      Time     Phase       Cut
         620026    620026              0         0         0         0
===============================================================================
   Grand Total      Good   Bad:  Region      Time     Phase       Cut
        620026    620026              0         0         0         0
   in  99174.     seconds
 Image            has   620026 counts for  6.252     counts/sec
xsel:AXAF-ACIS-FAINT > plot image
Now let us suppose we are interested in the data collected by chip S3. We select events and GTI for this chip... 

xsel:AXAF-ACIS-FAINT > select chip s3
Processing file: /local/genji/data3/kaa/SSA13/primary/screened.evt
Set XYCENTER to   4317,   3877
and XYSIZE   to   1478
with current binning image will be    370 x    370
Note that the select chip command has scanned the output events and found the min and max in X,Y coordinates. It automatically sets the XYCENTER and XYSIZE to cover these min and max so any extracted image will only be of the part of the focal plane occupied by the selected chip(s). Before doing anything else we make sure that we don't lose this new event file by saving it... 

xsel:AXAF-ACIS-FAINT > save select
> Give output file name >[] s3screened.evt
Now we want to make a maximum resolution image of the selected chip so we reset the xybinsize and extract... 

xsel:AXAF-ACIS-FAINT > set xybinsize 1
xsel:AXAF-ACIS-FAINT > extr image
extractor v3.79  21 Jun 2000
 Getting FITS WCS Keywords
 Doing file: /local/genji/data3/kaa/SSA13/primary/xsel_work1001.xsl
100% completed
          Total      Good    Bad: Region      Time     Phase       Cut
         278323    278323              0         0         0         0
===============================================================================
   Grand Total      Good   Bad:  Region      Time     Phase       Cut
        278323    278323              0         0         0         0
   in  99174.     seconds
 Image            has   278323 counts for  2.806     counts/sec