The sharpness of the line is dependent on how clear the liquid is. If the liquid is hazy or has a bunch of particulates in it, the line will be hazy. If the liquid is bright - transparent - the line will be sharp. When I take readings during fermentation, I always filter the biggest particulates out so I get a "line" maybe one degree of SG wide. Oh, and my refractometer is a relatively cheap model, in the $40 range.Mine is cheap (Amazon ~$20), and it has a blurry line even with focusing, and if all is as it should be...
Has anyone experienced this, would the investment of ~$60 be worth it for a quality built refractometer ?