The sun gives off a heck of a lot of infrared, but the water in the atmosphere absorbs some frequency ranges. There's a pretty deep valley around 940 nm, and 94

The sun gives off a heck of a lot of infrared, but the water in the atmosphere absorbs some frequency ranges. There's a pretty deep valley around 940 nm, and 940 nm illumination sources are cheap and readily available. Combined with a sufficiently narrow bandpass filter, sunlight may be less of a problem than you expect.