Mg emits radiation at 285 nm. Could a spectroscope be used to detect this emission?

You can not use a spectroscope to detect this emission

Explanation:

Visible spectroscopy is one of the most widely and most frequently used techniques in chemical analysis. For a substance to be active in the visible one it must be colorful: that a substance has color, it is because it absorbs certain frequencies or wavelengths of the visible spectrum and transmits others.

The visible range is considered from 380 to 750 nm. The range of the near Ultraviolet or Quartz is 190 to 380 nm.

The spectroscope is an instrument that allows us to determine the different regions within the visible spectrum (380 to 750 nm wavelength), in this case the Mg emits radiation at 285 nm so it would fall into the ultraviolet spectrum and would not be Visible to the human eye and therefore could not be detected with a spectroscope.