Problem(s) Encountered:

While taking spectroscopic and photometric flats, there appeared a dark blob right of center in each image. Tried to  change roi to see if it stayed. After chatting with Justin & Eric, probably something on the collimator lens or detector window. Not sure when/how it would have happened, the darkhatch and mirrors were closed while the dome was opening. Per Eric's advice, I took an image at a higher airmass to see if it stayed in the same region or if it would be out of the way but it was persistent in staying there; also took an  image with the slit position indicated in the guide star selector as a test, but the artifact/blob remained. Eric said he will have to take a look at the instrument in the morning.[Clouds were an issue so this did not result in a huge loss of hours in and of itself in the end.]

Solution:

Considering that the spot was resolved in spectral and direct imaging, it had to be somewhere below the dispersive element. Lowered the detector this morning and found a lady bug on there.  Blew it off and all is well.