My goal was to find a solution very easy to build, without sacrificing too much performance, as often happens with the home-made examples, so far with razor blades, pencil-sharpeners or similar, thath gave me performance rather limited. I was also looking for some kind of reflective solutions, to allow proper tracking of the stars during the exposures.
The easiest thing that came to my mind was to cut a piece from a mirror of good optical quality, recovered from a copier, and practice at the centre of its reflective surface a very thin line with the tip of a sharp cutter against a guide, applying a very minimal pressure, so only carry reflective scratch without causing absolutely no etching glass substrate. (photo 1 & 5 ).
I immediately stuck with tape this mirror to my simple modular spectroscope, instead of its origial slit, and pointed at the Sun. As expected, the remaining transparency of the reflective layer lit up the image a bit, by preventing the observation of the absorption lines, but it was enough to apply at its back a piece of black paper in which I cut a narrow window ~ 1 mm wide, corresponding to the mirror slit, to see a myriad of absorption lines with a fineness rarely achieved even with expensive commercial slits . A fantastic image, compared with the extreme simplicity of my construction!
Encouraged by this initial result, poking a little in my hobby lab, I immediately made a montage a little less precarious, as shown (photo. 2).
I installed this new slit on my simple modular teaching spectroscope, equipped for the occasion with two lenses of old reflex 200mm / F4, 5 (bought on eBay for a few bucks) and a grid of 1000 lines / mm, blazed (photo 4) . This simple equipment so realized has been more than adequate to show perfectly even the finer and weaker details. Than I applied the camera and made some images, from which I have extracted the first examples here.
NOTE: The slit was mounted with the reflective surface facing the Sun. Solution planned for possible future use for star tracking (photo 3)
The image 5 is a section of the slit photographed under a microscope greatly enlarged.
Note, for example, a small extract around the triplet of Mg ....
These are only the earliest recorded images.
However, other latest images show further significant improvements and will be included here soon.