The geiger counter went on a high altitude mission last week.
It traveled together with a (arduino) transmitter under a high altitude balloon up to an altitude of 30km.
I designed a shield for the arduino mega containing a GPS, SD, Temp Sensor, 433Mhz transmitter and some IO.
I’m now working on a single board version.
Condensation could indeed be a problem as temperature rises again at this altitude.
Going to look into it .
The radiation should keep rizing with altitude as its cosmic radiation.
But its also something I have to look into.