From: '''newspam'''@nonad.co.uk   
      
   On 28/11/2025 10:31, Don Y wrote:   
   >>>  > Much like a regular Joe would do:  "It's cloudy tonight.  No need to   
   >>>  > protect   
   >>>  > the cold sensitive plants as it likely won't get very cold."  His   
   >>> knowledge   
   >>>  > of the past/future isn't anywhere near as specific as that of a   
   >>> machine   
   >>>  > -- yet,   
   >>>  > serves him well (enough).   
   >>> For that you probably want windspeed and a simple skyward and ground   
   >>> facing thermocouple pair   
   >>   
   >> Preferably coated with something having a high emissivity in the far   
   >> infra-red.  A small piece of Kapton tape folded over each junction   
   >> would be fine for initial testing.   
      
   Any pigment carbon black paint will do. Even white paint is black in the   
   thermal infrared band. For this reason modern observatory domes are now   
   painted with a hybrid aluminium/white pigment so that after dark the   
   dome surface does not supercool and cause cold air to drip in through   
   the dome slit creating avoidable turbulence.   
   >   
   > Do I need that much more "resolution" than simply imaging (sky and soil)   
   > with an Ir camera?   
      
   The idea is to have a two pixel imaging system consisting of a pair of   
   thermometers with low thermal inertia one facing upwards shielded from   
   the ground and another that is ground facing and shielded from the sky.   
      
   The temperature difference and its rate of change gives you the extent   
   to which the situation is likely to allow a frost and/of fog to form.   
      
   You also need windspeed and relative humidity. This is probably the   
   simplest kit configuration to predict risk of frost of fog.   
      
   Dew point was always very important to astronomers and highway traffic   
   monitors so you can get purpose built kit for this sort of thing.   
      
   --   
   Martin Brown   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)