My Month-Long Battle Against Moisture (Part 3)
So I’ve had those sensors I mentioned in part 2 running on my Night Sky Pi through all of May. We’ve had everything from scorching hot days to some pretty nasty storms, so I think I’ve collected enough real-world data to figure out what the heck is actually going on with my setup.
Results
Before diving into the data, I had to clean things up a bit. There were chunks of time when my internet decided to take a break, meaning the weather API couldn’t be reached. I had to strip those periods out from all the datasets to keep everything comparable. Once I did that and lined everything up properly for graphing… well, something jumped out at me right away.
My sensors were running WAY hotter than what the weather API was reporting. At first I thought they were broken, but then it hit me - they’re sitting in direct sunlight with practically zero airflow. Of course they’re cooking!
Open Weather API vs External Sensor
Looking at the graphs, you can literally see where day turns to night - those temperature spikes are like clockwork. The external sensor consistently shows these crazy peaks compared to what the weather API reports. The sensor itself isn’t lying - it’s just that its little housing is basically turning into a mini-oven when the sun hits it.
What’s interesting though is how quickly it cools off in the evening. The temperature actually drops faster than the API reports, probably because by late afternoon my setup gets some nice shade and cools down pretty rapidly after sunset.
External vs Dome Sensors
If I thought the external sensor was bad, the dome is a complete disaster. It’s showing the same spiky pattern but reaching absolutely bonkers temperatures - we’re talking 70°C (158°F)!
What’s happening is pretty clear: the dome is acting like a greenhouse, trapping all that heat with nowhere to go. Add in the electronics inside generating their own heat, and we’ve got a serious problem. No wonder I’m having issues with condensation - hot air holds more moisture, and when it cools down rapidly in the evening, all that moisture has to go somewhere (namely, all over my camera lens).
These temperatures aren’t just annoying - they’re going to absolutely murder my hardware. We’re talking shortened lifespans, potential failures, and definitely poor performance. So my evening moisture problem isn’t even my biggest headache anymore - I need to figure out how to stop my equipment from basically slow-cooking itself every sunny day.
Conclusions
Looking at all this data, it’s pretty obvious I’ve got two big problems with my camera setup, and they’re feeding each other. First, there’s the moisture issue I’ve been obsessing over, but now I can see the real villain is that ridiculous heat buildup in the dome. The physics is simple but annoying - hot air holds way more moisture, and when it cools down fast (which mine clearly does after sunset), all that extra moisture has to go somewhere.
So instead of just focusing on dealing with moisture, I need to tackle the root cause - that greenhouse effect turning my dome into a sauna. I’ve got to figure out some way to get air moving through the system. Maybe a small fan system that can pull in cooler outside air and push out that hot stuffy dome air? Getting the temperatures more balanced with the outdoors should automatically reduce how much moisture condenses when evening rolls around.
The Remaining Moisture Problem
Even with better airflow, I’m not naive enough to think the moisture problem will completely disappear. There’s still going to be some condensation when temperatures drop at night. My plan is to add a simple heating element - probably just a ring of resistors around the inside of the dome that I can switch on when the temperature gets within a few degrees of the dew point.
The combo approach should work pretty well: circulate the air during the day to prevent heat buildup (which reduces moisture capacity to begin with), then use minimal heating at night to keep the dome just warm enough to stay above the dew point. It’s not exactly rocket science, but hopefully it’ll keep my lens clear and my equipment from cooking itself! I’ll post updates as I implement these changes and see if they actually work in the real world.