Pardon my taking liberties with the terminology for equipment relating to observing/recording astronomical spectra. From the multitude of ray-traced diagrams and other postings of scope designs I've seen, all attempt to avoid chromatic aberration... and understandably so! However, some optical designs seem to naturally create a really well-defined spectrum - which is the point of the tools for spectral observation, is it not??
With such designs in mind, whether done intentionally or the result of just poorly performing designs, can't these designs be used as is or be lightly 'tweaked' for use in spectroscopy? What I mean is that some designs just seem to need neither slit nor diffraction grating (reflective or transmission) to generate a clear spectrum (some vastly clearer than others, of course). Or, is it I just don't know how to interpret those diagrams and designs that show all the pretty colors all neatly separated and lined up - ripe for the picking by eye or camera?
I am hoping for some insight so it can help me understand more detail and theory involved in the design of some spectrographs out there. I've seen many web pages that go through the calculations for what follows once a "pinpoint" of starlight is obtained but it seems to first combine all that light that was once (maybe) already well on its way to producing a full blown spectrum.
It just seems like a lot of "re-engineering" is being made to undo what is naturally occurring in some basics optics - only for it to be redone by, yet, more optics. Just look at some of those designs in the "Post your Optical Design!" thread for some examples. What am I missing, here??