Confusion between Science Slit List and Mechanical Slit List

[Andrew DeGroot]

Hi Nick,

 I have encountered a new and strange event while reducing data using the DRP. I am using the latest DRP version, v20140610, to reduce data taken in June 2014. When running the step, Wavelength.fit_lambda_interactively(), I encountered the problem that some slits refused to display for wavelength fitting. Looking into this, I found that in CSU.py around line 249 (this is where you map the science slit number to a mechanical slit) the science target fails to be found in the mechanical slit list. Further digging shows a peculiar detail that is present from the beginning when the DRP first creates the science slit list and the mechanical slit list from information in the image header, in IO.py around line 366. The science slit list contains all the correct slit names for objects placed on the science mask configuration, but the mechanical slit list displays a list of names that corresponds to the alignment mask configuration including all the alignment stars.   

I hesitate to call it a DRP bug because it is a pretty confident assumption that the mechanical slit list should have the science slit mask targets on it but I am looking for a workaround if possible. I have tried a few fixes myself but none will allow the DRP to correctly reduce the mask. I have now had this problem on three masks taken on 2 nights which may be evidence of a user error or a bug during observations. Any help you can provide would be great appreciated. Thank you. 

-Andrew DeGroot