...
### object obj_id posslit objtracefile
0061 RXJ2248 NGC4258 3 A fire_0059.fits
0062 RXJ2248 NGC4258 3 B fire_0060.fits
0063 RXJ2248 NGC4258 3 A fire_0059.fits%
0149 RXJ2248 3 A fire_0154.fits
0150 RXJ2248 3 B fire_0155.fits
0151 RXJ2248 3 B fire_0155.fits
0152 RXJ2248 3 A fire_0154.fits
### posslit
0059 A
0060 B
---------------- end of snippet ---------------
The line beginning with ### is critical, as it tells firehose the format of the subsequent lines of text. The "###" field denotes an exposure number, then the next 4 fields are keywords to be edited in the fire structure. OBJECT is the object name, which needn't be edited, but I like to change it so I know which objects I'm extracting, then obj_id is the unique number given to each object to group them for reductions (these two should already be set).
POSSLIT and OBJTRACEFILE are as described above and need to be set - these are the fields that will set the reference star exposure. In the case above, frames 59 and 60 are telluric exposures taken just before frames 61, 62, and 63, which are science exposures. Frame 59 is in the A position, and 60 is in the B position. We make sure that the posslit field in 59 and 60 are set correctly in the last few lines.
Once you set these properly, the code will run reference star object tracing when selected during extraction.
In case you are interested in what happens when you run this: The code matches the centroid of the object trace to the centroid of the reference star. Then, it calculates the FWHM of the reference star. FIREHOSE performs sky subtraction, masking out pixels within 2sigma of the trace (with sigma determined from the reference star fit) during estimation of the sky. After 2d sky subtraction is finished, it performs an optimal extraction using the reference star's spatial profile, unless boxcar extraction is selected, in which case it performs a simple sum.
If you are feeling adventurous, it is possible to create co-added 2D, rectified spectra of each order. For this, you have to run firehose in reference star mode as described above, and then you can take a look at "fire_addrectified.pro" in your $FIRE_DIR/Utils location. That is not presently supported but you are welcome to try it as well as fire_extrectified.pro (although the latter is still in development).