Animation question

How can I make this animation look less choppy?

I used Animation Shop 3 for the animation. The frames are set at a 25/100 second interval. The frame pictures themselves were created in Photoshop 7. There are four of them and each was turned at a 90 degree clock-wise angle and then saved to be added to the animation.

I think the angle rotation is the problem but I could not figure out how to do a smaller rotation using the arbitrary rotation tool without making the picture itself shrink and rotate with the added white border.

I hope all that makes sense and would appreciate any help anyone could provide.

Cheers!