This picture contains the final result of 60mm. This happend to be the final sparklenght, because I selled it on Ebay the next day. I wasn´t very satisfied because the lenght not even equals the windinglenght (75mm). Maybe I build a better one some times.
Here you see a strong corona field that rises between Primary and Secondary (not good!)
Here you see that I got lots of primary hits, but the obit still works.
Here you see a light ion-field that builds up from the ground-connected wire