How can I stop DiskUtilities from requesting permission every time I try to create an image from a CD
Mac OS X Snow Leopard is a DVD not a CD and I'd imagine some of the other discs you're trying to copy are DVD's too. Anyway, I can replicate your situation however, I also can do it from Disk Utility without being prompted for my password.

To do that, first unmount the disc and then select the parent node, e.g. on my Apple SuperDrive it's HL-DT-ST DVDRW GX40N, and option-click (right-click) and select: Image from HL-DT-ST DVDRW GX40N Media

In the subsequent dialog box change Save As: to something more user friendly, and change Format: to: DVD/CD master

Click the Save button and the disc will then start coping without being prompted for your password.

When finished click the Done button. 

You can mount then disc image by double-clicking on it in Finder.



The above instruction are for Data DVD/CD discs  not Audio CD discs. Also note that I do not have a Hybrid Data DVD/CD/Audio CD disc to test whether or not the method shown above will work with that kind of disc.