During an exposure, the imaging sensor of a DSLR warms up, resulting to noisy images. By cooling down the sensor, it is possible to eliminate or somehow minimize this thermal noise.
I have made a number of attempts to accomplish this with a Canon 450D and a Peltier module, however, it appears it is very difficult to implement without running into problems such as condensation and frosting.
Related link: View all home-brewed DIY astronomy equipment
Night Sky in Focus © Anthony Urbano | Bacoor, Philippines