Hey Ken, Nice work there. I too had exactly what you have installed. A 4x4" treated beam but with a 10’ steel commercial grade pipe (also Lowes). I found that even with cement in the ground the weakness in this design is the attempt to increase the height of the pipe (PVC or steel) higher. The higher you go the more sway you will have. I have mine mounted on top of a sand dune on the beach where 50mph winds are common in the winter. The higher I tried to cheat the pole up the fasterners the more sway and vibrations leading to false precipitation there was.
It appears you have a very nice chimney there on your house would you consider using a multiple metal strap and steel pole combination to elevate Sky above a safe zone from fireplace heat??? The good news is Sky won’t care if the temperature is off a little (of course too close and you’ll melt Sky).
If you don’t want or can’t do a chimney assembly, I’ve reverted to 6 bags of cement ($2.64 60lb bag)
and a 16’ beam of 4"x6" with an 18" heavy duty PVC pipe. (see image).
I’ve had NO false readings since I used the height and “beef” of the 4x6 and just a little 18" of PVC.