I’ve used a lens from quality sunglasses over the lens of an outdoor installation, and after 3-4 years it has suffered no noticeable loss in picture quality (detail, contrast, colours). So, as the above answer suggests, a rudimentary filtering out of the useless UV would be helpful. Have a look at outdoor CCTV cameras for industry use (factory perimeter e.g.). The polarized glass is one thing, but these cameras stay online for a decade in all weather.
It’s just a 640x480 streaming ethernet (I think I used wget+curl to grab jpgs, and perhaps vlc to grab the stream) camera with manual focus, so installing the overlay (the sunglass lens) was trivial. It faces direct sunlight max 5 hours per day. There has been no noticeable degradation in the images. I have not made a baseline with an unfiltered lens. Google UV lenses for CCTV cameras; your wide lens needs something bigger.
Trivia: the PV / solar panel crowd have done a lot of interesting research into what diminishes the effect of their panels... I would test a filter over a 5V cell, and see the current with a multimeter across a low-ohm power resistor. Anything that gives high transparency, but very low current - compared to the unfiltered baseline - would probably be a good filter. Glass with a metal component alone diminishes effect a lot.
Also know that professional installations often utilize a small heating element (a power resistor would do, or some nichrome wound around a ceramic element) to ‘push’ out dampness and condensation. It would be prudent to use a thermocoupler (MAX6675 on I2C is ok, and low-power) to turn that heating element on/off w. a MOSFET (IRF3202 is very good, but perhaps overkill, needs 10V to gate for full on, NTD4906N is logic level and a better choice), or a DS18B20 (onewire?) A DHT22 (I2C) would let your system know both temperature and humidity, and then trip heating element based on ambient humidity. Essentially, humidity is dissipated if internal temperature exceeds external temperature. I heard this from an electrician who installs camera systems. To further protect electronics, they can be coated in nail polish (Great scott made a youtube video about this), or embedded in epoxy.
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