I had a quick question regarding testing of CYA. I know the directions for the test state to be in full sunlight with your back to the sun, tube at waist level, etc. etc. However, when following these instructions, the 50 ppm CYA standard that came with my test read approximately 30 ppm instead of 50 ppm. I have read from a couple threads that the correct practice is to just "find a testing place where you get 50 ppm", since the standard is pretty accurate. Is this definitely the right way to treat the standard? I'm asking because I want to make sure I do the test properly, and I will likely have to test it in vastly different conditions than the directions say to get it to read 50 ppm.