Tämmösen löysin;
Using Pavel’s formula: Focal Length/(Range 150-200) = Bar Thickness + Inter-Bar Gap, I came up with the following design for my Tak Mewlon 180mm F12 with a focal length of 2160mm.
2160/180=12mm, giving a Bar Thickness of 6mm and an Inter-Bar Gap of 6mm.
NOTE: The divisor range of 150-200 allows for a Bar Thickness/Bar Gap dimension that doesn’t come out as an awkward value of, say 6.5735mm.