You asked
Is the nikon d6 good in low light?
The D6 is a full frame camera with a 20.8-megapixel sensor, and full frame is the size that helps most in low light. The sensor guide explains that a bigger sensor collects more light at the same framing and f-number, which is why what a bigger sensor buys you is worth reading.
The lens matters as much as the body here. The D6 has no stabilisation in the body, so for slow shutter speeds, use stabilised lenses. For dim scenes, I'd look at fast primes like the Nikon AF-S 85mm f/1.4G, the Sigma 35mm f/1.4 DG HSM Art, or the cheaper Nikon AF-S 50mm f/1.8G. The primes or zooms guide explains why they gather so much more light.
Written by Claude from this site's pages.