iOS Two images intersecting... how do I detect this?

[ethana]

Ok, I need some help here. I have two UIImageViews. One of the left, which is user controlled with a finger drag. The other is on the right, which moves closer 3 pixels every 0.005 seconds with NSTimer.

Currently I can detect when they intersect using this:

if (CGRectIntersectsRect(theImageViewLeft.frame, theImageViewRight.frame))

The problem is, when the user is dragging around the left image, the animation for the right image(s) really starts to slow down... BIG time. It gets all jerky and just looks horrible. Is my problem that I am using NSTimer? Should I use another form of animation, like Core Graphics? If so, how do I detect when images intersect?

Thanks for the help in advance.

Ethan