CD31 resolution tests

We took C2H2 Q branch spectra in himed and med modes with all slits and the pinhole.  We also took rinsed cell spectra to go with them.  Script and save files are in analysis/cd31/specfocus.

I used the pinholes to trace the path of dispersion and find the dispersion in wn/pix.  I used a linear fit for wn/pix, although a quadratic would probably be <=3% better.

I used clickfit to fit along pixels and corrected for the fact that the slits didn't run along pixels later.  This was a small effect.

For the high-med, I fit Q(9)-Q(15) and Q(15)-Q(19).  For the med, I fit Q(10) through Q(23) along with R(0) and skipping Q(20) because of a hot band.  As the slits got wider, the lower lines really blended together.  In fact, no fits were good for slit 6.

In all cases, I fit many rows of each line and then took a median of all the fits that looked good for a particular line in order to calculate the resolving power in the bottom figures.

himed Q branch with slit 4 (rotated 90 degrees in IDL to work with clickfit)

med Q branch with software rotate and only Q(10)-Q(23) (right to left) extracted

himed resolving power as a function of x pixel.  Each slit is different color.

Medium mode resolving power as function of X pixel.  Each slit is in different color.  Predictions from ETC are horizontal lines with appropriate color.  Note that Slit 6 was so broad that the fits didn't work.

After finding that C2H2 med mode was ~85% of the prediction, which seems reasonable since we bias ourselves toward the high resolution, we looked at H2O at John Carr's 1838 cm-1 setting.  The actually wn0 is a little different to provide good lines to fit.  

Followed the same procedure with pinhole and all slits.  The lines were present in the cell even when continuously pumping.  Used an aluminum plate right in front of the window and adjusted the level in software to provide a good reference.  Chose to divide rather than subtract.  

Got resolving powers that were far below ETC prediction.  We're going to look at more settings going toward longer wavelengths.  Will check the ETC, too.

Resolving power for 1838 (nearJohn Carr's H2O setting) as a function of x pixel.  Note that  the line  near x=850 was the brightest.  The fits make me think maybe it was resolved by the narrowest slits.