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Rom,
The original slit was two polished stainless steel blades, which could be "set" to any nominated gap width. The latest LhiresIII uses a chromed multi-slit plate (4 slits).
We found it VERY difficult to cut and polish s/s slit jaws to the required accuracy; then position them to maintain parallel, square surfaces to give the required consistant guide star image. In the end we gave up.
The Astronomical Spectroscopy group has recently got around this problem by designing, developing and getting OVIO (France) to make a Custom chromed reflective slit plate. This plate has 9 slits (100 to 20 micron) and three pinholes (100 to 20 micron). These are now available to members.
We are currently designing and prototyping an indexable holder and guide transfer mirror/ lens system (this will also incorporate a flip mirror/ lens system for reference lamps).
Hope this helps.
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