Criterion RV-6 Fan Cap

Used to equalize the telescope's internal temperature with the environment, and to keep the mirror below the dew point. I think? I don't know, I'm still just starting out and the weather hasn't been great for imaging, so I designed this in my boredom.
I use a 12v 40mm Noctua fan with the included speed limiter wired to a barrel jack to use with the rest of my 12v astro gear. You could add a switch by drilling an appropriately sized hole.