Tony, I propose a summary of the actual situation...
The UVEX initiative proves that it is possible to produce a spectrograph meeting the initial requirements: high-performance for a reduced cost.
The main high performance concerns the very broad spectral coverage allowed by the use of an achromatic optical configuration (a nearly « all mirror » solution) and a minimal optical surfaces number. We are also helped by the providential new generation CMOS cameras i.e. very consistent qualities with our need: low price, back-illuminated sensor with high quantum efficiency and extended spectral range.
The reduced cost come from the use of simple spherical mirrors available on the shelf, the same for the grating, and a stripped optical formula. In this sense, the « 3D printing » solution is technically credible in a context of industrial production, as well in a context of a by itself realization (diffusion of CAD design). The critical components prepositioning also simplify the adjustment procedure - thanks to the « 3D printing » !
The project is however far from being finalized, besides adjustments concerning CAD, it is necessary to underline two points:
(1) At this stage, the spectrograph can not be placed in all hands due to the lack of a narrow slit guidance/pointing system. Without such a device, the use of the instrument is not a simple task. For the same reason, the productivity is seriously affected, even though the radiometric efficiency is intrinsically high - so we are wasting a lot of potential here. Implementing this slit system in a very small volume is not an easy task. Nothing is however insoluble, but there is still work ...
(2) The astigmatism of Czerny-Turner formula is only partially corrected by the use of a classical cylindrical lens just in front of the detector. For an almost perfect correction and as an option, the use of a variable curvature radius cylindrical lens along the spectral axis is a fine solution. We can use the optical machining technology called "free-from" to achieve this result, which has a cost. UVEX can work without this enhancement, but this makes the instrument almost perfect.
So there are some milestones to go through, but UVEX has fascinating capabilities and is leading the way in the generation of instruments that can further democratize spectrography and produce more and more scientific data.
So you have to be a little patient (my job is optics, but mechanics and CAD it takes more effort for me
Christian
