Hubble Space Telescope Highlights for July and August 2014

The WFC3 visible light camera is actually two physically separate CCDs put right next to each other. There's actually a small gap between them in the images by default, for the sake of making an intact-looking image I closed that gap as much as possible, but there's still going to be either a seam in the images or you'll see that they're slightly disjointed since there's physically a small gap between the pixels on one CCD and the pixels on the other. Leaving a small seam is actually less visually distracting.

[link to documents.stsci.edu]

On some images they'll actually take an additional image with the pointing offset from the rest of the exposures just enough to cover up the gap with image data. The NGC 6744 image is an example of this. They don't always do that though, these images were all taken for scientific reasons, not to make aesthetically pleasing images. I'm just taking raw scientific data as they release it and doing my best to turn them into aesthetically pleasing images.