https://joe-cali.com/eclipses/EQUIPMENT ... lters.html
After 19 years, I found a pinhole in the Baader Astrosolar filter I made in 2004 for my ED80. Time to make a new one. I could have simple made a new filter sandwich and kept the old flange for the tube but I decided to try something different. I found some pieces of clear anodised 1mm thick 150mm wide aluminium sheet in an engineering shop scrap bin (bonus). I put two 5mm edge bends on it then cut it on a table saw to 140x140mm squares.
Next I cut two sheets of self-adhesive foam core sheet to fit exactly inside the bent metal sheet. I cut two 116mm holes that were a tight fit so that this flange fits neat and very tight over the lens hood. Once on it takes considerable force to remove it so no accidental blow offs.
The 76mm/3 inch hole is a few mm smaller than the objective's 80mm
I used the two circular cutouts to make a circular filter sandwich. One self adhesive circular piece is stuck to the aluminium piece, the Astrosolar film is sandwiched between this piece and the second piece. The filter material is now recessed about 1/4 inch 6mm from either surface. This protects it from accidental damage even if dropped unless it’s dropped onto a sharp object.
Here is the filter on the ED80
And here is the filter and holder bundled up and safe with covers over both sides of the filter. Ready to be packed for travel to next months total eclipse.