Roger Clark has done a very extensive and technical review of the sensor performance of the Canon EOS 7D Mark II and how it relates to the original 7D, astrophotography and general photography needs.
This review is well worth the read.
From the review…
“The data shown here for the Canon 7D Mark II indicate that the camera is operating at near perfect levels for the sensor with lower apparent read noise and impressively low pattern noise compared to all other current Canon cameras tested and better than that in the 7D Mark I. This means that for high signals, noise is dominated by photon statistics. Sensitivity is improved 14% over the 7D Mark 1, and the sensitivity per square micron is the highest that I have measured for any Canon camera to date.
The approximately 10x lower thermal dark current is a game changing factor, making this camera the top Canon camera for long exposure low light photography that I have tested. The superb autofocus system, comparable to Canon 1D series pro cameras with 65 autofocus points is another game changing innovation, as the camera is at a price point that is affordable to more people.”