The JMI Telescopes Piggyback Camera Mount allows you to attach any camera to the outside of your telescope. This can be done with altazimuth-mount scopes for shorter exposures of up to about 7 minutes, but for sharp pictures free of star drift that go beyond that time you'll need a properly aligned equatorial-mount telescope.
This version wraps around the optical tube assembly and works with Celestron's NexStar 4, 4GT, and 4SE series telescopes.