He will use it for astronomy - star and planet gazing. Thanks for all comments so far!
This is a nice scope around $500.
http://www.telescopes.com/telescopes/catadioptric-telescopes/celestronnexstar127sltcomputerizedtelescope.cfm
One bit of advice I would give is that the quality of the mount is just as important as the telescope itself. If you can get something with a sturdy equatorial mount that has a computer drive, it would be worth the money you pay for it. In the link above, the equatorial mounts are those where the telescope doesn't sit directly on the tripod but instead is fixed to a small arm with counterweights at the other end. Without getting too complicated ... this arrangement allows the "arm" of the mount to be pointed at a single point in the sky around which the telescope can rotate to maintain its focus on an object as the earth turns.
I'm not sure what the circumstances of this gift are, but is it possible for your husband should be involved in selecting it? I don't want to ruin a surprise gift, but with this kind of thing I'd want him to be comfortable with what he's getting before you spend the $500 on it.
You can see a very good offering of scopes at Orion Telescope and Binocular http://www.telescope.com/
Long focal ratio refractors are the best for planetary viewing, shorter focal ratio reflectors and refractors for deep sky. Whatever you pick out, get a really solid mount. The stuff at Walmart, etc. is junk. A bad mount will spoil any desire to pursue star gazing further. I’d go for a manual mount rather than an automated one. You will learn to locate stuff (not that hard) and it takes time to set up the auto mounts. Also, get a mount with slow motion controls. Not sure if you can squeeze this into $500 but you might come close. Feel free to Freepmail me with any questions. I have about 8 small scopes - all refractors.
If your husband hasn't worked with small telescopes before, he should be prepared to be a bit "disappointed" with what he sees in the sky. Any impressive color images you see in telescope ads don't really look anything like what you see in the sky. Most objects in the night sky are far too distant to show any kind of colors to the human eye, so the photos you see are typically done using a camera setup on the telescope with a motorized mount that allows for extended film exposure to bring all those colors out.