By using an equatorial mount to track tlie stars during an exposure, you can reach deep into space and record fainter targets.
The next step up in complexity still uses the camera's own lens to shoot the sky, but now the camera rides piggyback on a platform that follows the stars. The advantage is that stars will record as points, even in 10- to 30-minute exposures. Because the exposures can be so long, a piggybacked camera is able to capture stars and nebulosity far fainter than any stationary camera will record.
However, the platform must be aligned as closely as possible to the celestial pole. As the focal length of the lens goes up, so does the intolerance for poor alignment. For example, telephoto lenses with focal lengths of 100 to 300 mm demand alignment within 1/5 degree. Just aiming at Polaris or Sigma Octantis will not be sufficient.