Solar filter for binoculars (with 42mm objective lenses)

Solar filter for binoculars with 42mm objective lenses.  These work both on my Nikon Monarch HG 10x42 and Nikon Monarch 7 10x42 binoculars and will probably fit other similar sized binoculars.

This solar filter fits nicely on the end of the binocular objective lenses. It is held on by friction fit and won't fall off on both of my binoculars. The inside diameter of the body is 54mm, so measure your binoculars to see how well this works - you can probably scale this up or down slightly to fit (scale the cap the same percentage). You will need the actual solar film to construct this as the 3D printed parts are only the frame. You can buy this on Amazon or any telescope supply company. I like both Thousand Oaks Optical “SolarLite” film, which gives a yellowish cast to the sun, and Baader AstroSolar ND5.0 Visual solar film, which gives a more natural white (slight bluish) cast to the sun. Each A 4"x4" sheet is just large enough as the actual film is cut to a 55mm diameter each. Use the cutting template and razor knife to cut the film.

This is a threaded design the the solar film is held in place by pinching it in between the body and cap. They are threaded with a ultra-fine M56x1 thread.  This thread can be frustrating with 3D printed parts, but some patience is useful. Use a 0.4mm nozzle and very fine layer height for the threaded feature (0.07mm - 0.10mm layer height). Use variable layer height for the body as the rest of the body can be made with 0.30mm layer height. I like PLA+ for these and have had better luck with PLA+ than PETG for fine threads like this.  I've added a loose fit cap that can be useful to at least getting the threads started on the body. Work the threads in by twisting back and forth and then cleaning any plastic debris/dust and the then the threads should be relatively smooth. Finally, assemble the filter with the film.