HI Big_Eddy, hehe I was sure I'd hear from you!
All I know is one is called a Quebec hydrotherm (got mine from Covell's, SKU is HA-MHYDQUE5988. And the other is....*reading package*....a precision hydrometer.
So I am indeed dealing with two different beasties. And what is an atmospheric thermometer and how do you use it?
And yes the red line, whichever I am using, is always either right at surface or just slightly over. If it's more than 2 hashmarks over I fix it with distilled.
Been tapping since 2008.
2018 - 17 taps/7 trees...819l sap, approx 28l syrup
2019 - 18 taps/8 trees...585l sap, 28l syrup...21:1 ratio
2020 - 18 taps/8 trees...890.04l sap...gave away about 170l, 30l snafu'd....23l total for me from approx 690l
2021 - 18 taps/8 trees...395l sap, 12 l syrup
2022 - 18 taps/8 trees....7 sugars 1 red due to #2 having surgery so had the season off....582l sap, 18.5l syrup
2023 - 18 taps/8 trees...all sugars again. 807l sap, so far approx 14l syrup