Great video Kamil. I really enjoyed watching as a lot of work is involved here. Obviously based in the Alps you have a better chance of cleaner air because of the high altitude you can access. I not familiar with the tripod you are using but i have found that a video tripod (ball-head) with stabilised legs gives good stability. On the point about inspecting the exposed image, it is as well to check both the image displayed on the screen and also the Histogram. Best to trust the latter but with such a difficult subject it is perhaps even better to bracket exposures. Quite easy to do with the pro-camera when set in hi-speed mode. Cards are cheap but getting to these locations is not, so have a few handy. Another important point especially when working on long exposures and cold conditions is the state on the cameras batteries as this technique is very draining of power. I am not aware of any Reciprocity issues with digital cameras but film users need to be aware of this factor effecting exposure. I love you photos on UKC and we are lucky to have such a talented photographer posting on this site.