Hi,
Although the document is referencing solar observing have a look at this: http://www.spectrohelioscope.org/net/spectro.pdf
It’s essentially the same design as Cristian Buils work (a Littrow is a Littrow….) but using very basic components. I built this out of thin plywood and other scrap. I even used the objective from and old pair of binoculars, just like the spec and the only thing I bought was a “b” grade grating from Edmund Optics. It worked brilliantly! I even used it in demos about spectroscopy. You could beef up the design for telescope mounting without too much difficulty but without a way to view the slit it’s akward to use for stellar astronomy ( I tried and gave up…).
Anyway, it’s a very basic and cheap way to start.
cheers,
Bill.