You could perhaps build an imaging spectrometer something like the NMSU Acousto-optic Imaging Camera (NAIC) used for planetary work ? No need to isolate a point in the field. Just use it like a tuneable filter, taking the whole field and imaging the output as the wavelength is swept to build up a data cube.
AOTF-Based Spectral Imaging for Balloon-Borne Platforms
Journal of Astronomical Instrumentation, Vol. 3, No. 2 (2014)
http://www.worldscientific.com/doi/p...51171714400054
Sounds an ambitious project though !
Robin