Here is a link to the handbook. (dated feb 2016)
https://www.sxccd.com/handbooks/Handbook%20for%20the%20SX%20Spectrograph.pdf
The spectrum images there show very bad astigmatism, which is claimed to be an advantageous feature ! (It is not for serious use) though the spectra in the video did not look as bad as this so perhaps some improvements have been made.
Robin