The video astronomy revolution

The reason DSLRs are not used for high-resolution lunar and planetary work is that another, much cheaper, instrument works much better. Just before the DSLR revolution came the video astronomy revolution. By aligning the best frames from a video recording, it suddenly became possible for amateurs with modest telescopes to take pictures like Figure B.1, which were, until then, almost beyond the reach of any earth-based telescope.

The resolution of planetary images is limited by the turbulence of the atmosphere. By aligning hundreds or thousands of images, the video astronomer can see right through the turbulence. Air movements that are different in every frame cancel each other out, and what's left is what all the frames have in common, namely the true appearance of the planet.

What's more, imperfect tracking is actually an advantage. If the planet image moves all over the sensor during the recording, no single pixel or dust speck will have much of an effect.

Using a webcam or video imager

A webcam is a cheap CCD camera that delivers a continuous stream of video to the computer by USB or FireWire connection. These are commonly used for low-cost videoconferencing. For astronomy, the lens is unscrewed and replaced with an eyepiece tube adapter (Figure B.2). Because the IR-blocking filter is in the lens, which was removed, it is desirable to add a UV/IR-blocking filter at the end of the eyepiece tube.

Webcam adapters are sold by many telescope dealers.