Background
The
lspecfocus task is used for focusing LRIS in
spectral mode. With some tweaking, it can also be used to
investigate variations in spectral focus along the dispersion.
See the instructions below.
Requirements
- A set of spectral focus images, acquired with either a
longslit or multislit mask.
Procedure
- Launch IRAF on any HQ machine (preferable a fast one).
- Load the keck and lris packages.
- Run the lspecfocus task, being sure to set the
following parameters:
- logfile: set to the name of a logfile to save
- ndisp: set to the number of dispersion
subsamples to generate. Reasonable values are 3-5.
- Mark 1 or 2 desired slit regions to perform analysis.
- After analyzing a region, specfocus will
plot the variation in focus along the dispersion. At this
point, use the following keystrokes in the graphics window to
access different plots:
- b to display the best focus plot (the
starting plot)
- p to plot spectral profiles within each
dispersion subset
- s to plot spectra within each dispersion
subset
- w to display spectral widths within each
dispersion subset
- When done analyzing results, type q in the
graphics window to exit specfocus.
- If you selected a second slit region to analyze, repeat the
previous 2 steps for the additional region.
- When done, results are saved to the specified logfile for
reference.