Background image problems on resize, iphone/ipad

[Repost from How-to and Troubleshooting]

Hello all,

I have two problems with my background image at http://radiusensemble.org/

Problem #1
My blog is 960px wide. But my background is wider (1300px). When the browser is resized to less than 960px, the blog is no longer centered; it’s flush left. The resulting problem is that the blog does not align with the background image if the browser width is too small.

Problem #2
I just looked at my blog on an ipad and am horrified. The content loads just fine, but the background image, which is quite large, shrinks to fit the screen. Can I force the image to load at the same scale as the blog? I don’t care if the sides and bottom of the background image are invisible on a particular device; I made it large intentionally so that it would fill the screen. The “overflow” should be hidden, not shrunk to fit.

FYI, I have installed a mobile plugin and have a pretty good mobile version of the site that looks great on my iphone, but when I turn it off I see the same problem (#2) on my iphone, so this may be a safari mobile issue. Android doesn’t load the mobile site automatically, so this is an issue there as well.

Thank you for your help!