Zoom positioning on top: 0 still shows image at halfway point

[btmash]

I have a large image (see http://dpldams.dev.chillco.com/islandora/object/islandora%3A580) which I'm using jquery zoom on (the image is 4239px x 2856px). When I try the zoom in Firefox (any OS), the image zooms correctly. However, if I try to zoom in any other browser, the image zooms somewhat differently and top:0 is actually outside the parent element. Going to the top left corner correctly goes to the left-most side but the "top" ends up at the middle of the image.

I'm not sure if this is a zoom issue w/ other browsers though I'm somewhat inclined to suspect it is at the moment since it does work correctly in one browser.