Originally posted by angerdan The F* 300mm F4.5 is a very good lens, that's why i'd already recommended it here (there had be a copy for 530 bucks in Wyoming).
If you find it at that price you could buy it, it's a bargain. My specimen is better than this one in every sense and I bought it in Italy 6/7 years,
it is still an investment because it is part of those optics that are difficult to find and buy cheap.
I think the Sigma (Bigma) 50-500mm or 170-500mm are the candidates without duplicators or anything else.
Otherwise the 70-200mm f/2.8 for brightness but they are short, or you could go to the Pentax-DA 55-300mm F4.5-6.3 ED PLM WR.
A lot depends on how you want to use it.
Here the link
F* 300mm F4.5
Good Luck, Mario