Compute 2nd moments for Med Res data

With respect to determining the alignment for medium resolution exposures, as discussed today during the SpS hardware telecon, please compute using the 2D DRP second moments for the following medium-resolution HgAr visit sets:  

3443...3450
18052...18059

and the following lines:

696.7352, 727.494 , 795.0362, 912.5471, 966.0435

Note that as the above data are based on the HgAr lamp, the continuum needs to be removed.

These data would be used to compare with the plots generated by fmadec using the SEP python module (https://sep.readthedocs.io/en/v1.0.x/) in slide 12 of the following presentation: https://sumire.pbworks.com/w/file/fetch/140734437/LAM_Subaru_SM1_20200715.pdf

So a similar set of plots should be generated for this ticket.