I'll join the zombies.... Petr was right about my results improving with my digital refractometer. I've been using it long enough to conclude that its correction factor is effectively nonexistent, 1.00, with any apparent discrepancy with saccharometer readings attributable to the vagaries of eyeballing a thing floating in turbid, bubbly liquid. I am now confidently using mine throughout the process from mash to FG. I'm using the BF calculator which uses the Novotný cubic I believe, but this and the two Dave mentions all converge pretty closely and all, as Dave says, "close enough." In fact, I'd go along with "dead nuts."