I got my hands on some leftover stiff pink insulating foam. I cut some rough chunks to be manageable, and stacked them on top of each other to be able to make a matched set. I taped them together with painters tape so they’d stay together while I cut them. ?I had access to a hot wire cutter, and cut two concentric circles in the double layer. The inner circle matched the outer diameter of my scope, and the outer one was an extra 2” on the radius to make a rigid doughnut (4” total extra diameter). Hint: cut the outer circle first, so you can use the same center reference for both circles.

I sandwiched the film between the two foam circles, and glued it in place. And then I coloured the whole thing black with a marker, so it wouldn’t look so obvious. I put black hockey tape around the outside edge to reduce any chance of the layers coming apart. Bonus: it hides some of the imperfections. Works like a charm, and fits snugly.

One thing I would change: I glued it on a table top. Turns out my bottom-of-the-line scope tube isn’t quite round, so the filter is perfectly flat… until I put it on the scope. I’d suggest anyone doing this glue it together while the ring is on the scope, and mark which way needs to be up.

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