3" Feather Touch フォーカサー用 42mm 大型写真用フラットナー (SFF3-3FT-42)

I was worried about back focus spacing, but this flattener dialed in my stars edge-to-edge on the first try with the f-7 refractor. The 42mm chip size gives me room to breathe with my larger sensor.

The threads on this 42mm unit mate perfectly to my 3" Feather Touch, no adapters or wrestling required. Corners on my f-7 refractor are finally round stars across the whole chip, which is exactly what I needed for my larger camera sensor.

The stars in the corners of my images are perfectly round now, which was impossible with my old setup. Threading it onto the 3" focuser was straightforward and the fit feels rock solid.