Responsive Header Image

Hello,

I have made a website using the “Oblique” theme, and have just had a problem with the header image.

The website is currently not live, due to the work on it, but when I have uploaded a header image, in the ‘customise’ editor, it looks perfect, yet when I go onto the actual page, it gets all distorted and looks awful.

Whilst playing with it, I noticed when I made my browser window smaller, the header image once again went back to how i wanted it.

I was just wondering if there was a way to stop the header being so responsive, or if there was a way I could limit the width of the page, no matter how large/wide the screen/browser window.

Thanks

Aaron