Yes, the only way to accurately line up your scope is to put in in the exact same place every session. I have done this by accurately aligning first then down to the hardware shop for a bag of ready made concrete. Then, being very careful, lift each leg of the tripod up, scoop out a good few trowellfulls of soil (assume it is the lawn!!) and replace with mixed up concrete. level up the scope when you have made a little dent in it with the leg, and wait to harden. Repeat with other 2 feet. I have got 2 of these constructions at strategic locations in the garden depending on what trees I wish to avoid.
HINT Send wife to hairdresser so she doesn't see you cutting large holes in the grass. It works a treat.