Ok, that is not that bad. Just two more test to make sure. With the setup on the screen, move the times/div to the next step to the right, I just want to see a few more cycles in the screen. Then move the volt/div two steps to the left, making the instrument more sensitive to try to cover the whole screen from top to bottom.
I just want to make sure that is not a tube voltage problem, depending on the result of the above test it will seem that is not enough deflection being applied to the tub