I was able to capture the trail of the sun by stacking a 77mm B+W 10-stop filter, a Lee Big Stopper and a Lee 0.6 ND Grad Hard.
This is a single exposure of over 2 hours. Yes, it is processed from a single RAW file and there is absolutely no other external materials used from other exposures. It is not a stacking of multiple frames. No dark frame subtraction was performed to reduce the noise, and the battery life did not permit long exposure NR either. The sensor of the D800E is amazing in maintaining a control of hot pixels throughout the ultra long exposure. The sensor of the D4S looked so much inferior in terms of noise control, even for merely 45 minutes.
The greatest challenge was to keep the tripod safe from crowds.