Water inside pipe in my test give camera more time for escape
15% it is not deviation from zero
3-6% inside air also is not deviation
step by step when Earth is making rotation around own axis
camera see ( brightness ) step by step how change angle ( pipe angle to velocity arrow 30 km/s )
it is close to zero velocity ( perpendicular direction to 30 km/s ) and also it is close to maximal volume ( parallel direction to 30 km/s)
deviation of my camera ( NIKON 5000 ) can be near 5-6 % it is NIKON on stative and I'm using not natural LIGHT ( picture time is very long 8 sec. exposition ISO 200 , F 29 )
PLEASE INFORM NIKON THAT THEY HAVE DEVIATION IN CAMERA ( but not forget about special astronomy time , special direction , and geographic wide - I'm sure that NIKON will like Your story and they will like eliminate mistake form CAMERA
