Thanks David! Yes, I discovered the leaky sieve like nature of the shower tent at the onset of a big rainstorm (40 mm in an hour)
Ironically, once the tent was completely soaked through it no longer leaked - there was even a pool of ~ 10 litres of water trapped on the roof/fly the next morning.
I keep the scope/mount under a Telegizmos cover and a heavy duty tarp within the shower tent, which keeps me confident that the electronics + scope will stay dry.