The ‘H’ key: while zoomed in on an image hold down the ‘H’ key (this temporarily enables the hand tool) click and hold and the screen will zoom out to show the entire image and a box showing you your zoomed in canvass size. Move the box where you want it, release the mouse and you’re right back to your original zoom percent but now right where you want to be. Sometimes this can be quicker than the spacebar method if you want to move a large amount.