The only time I ever took an animal outside for sun was when I first got my turtle and, being kind of a surprise rescue, I didn't have all the equipment I needed for her. Even then she was in a box, as I never trust an animal to roam around on its own without running off.
The idea of taking any of mine outside just makes me cringe because there's so much that could go wrong, and I'd never stop beating myself up over it if something happened while I was doing something that the animal didn't even need or want.