Night! Camera! Action!
You may find this hard to believe, but for recording the Sun, Moon, and planets, these venerable tools all pale in comparison to the video cameras found in millions of today's households. No static drawing or photograph can rival the ineffable sense of reality and the emotional impact of a dynamic video recording. Richard Berry, one of the pioneers of electronic imaging for amateur astronomers, summed it up: "Seeing a video recording isn't experiencing the real thing, but it's the next best thing. Although it is impossible to reproduce the effect of a live video in the pages of a magazine, it is utterly wonderful to see the Moon, the planets, or the Sun on your television looking as good as they ever appear in a high-power eyepiece."
Each minute of videotape contains 1,800 discrete images, a number that dwarfs what even the most nimble photographer can achieve by tripping the shutter and winding the film-advance knob of a conventional camera! And just like with today's ever-capable digital cameras, video avoids the need to wait for film to be developed and printed to see your results.
The videographer has an insuperable advantage over the still photographer using film to capture fine details on the planets. Recording the colorful cloud belts of Jupiter requires an exposure of 2 or 3 seconds on a relatively slow, fine-grained film, while more distant and dimmer Saturn requires exposures of 4 to 8 seconds. But Earth's turbulent atmosphere limits the duration of perfect images to fleeting moments typically only fractions of a second. That's why professional astronomers are investing small fortunes to install adaptive optics systems on their telescopes that actually compensate for atmospheric seeing. With its ability to record 30 discrete images every second, video can be considered as "the poor man's adaptive optics."
Stills of the Night
"The moving finger writes and, having writ, moves on," lamented Persian poet Omar Khayyám. Both the visual observer and the still photographer must maintain an uninterrupted vigil so as not to irretrievably miss the all-too-rare moments when the air steadies and delicate details flash out in what legendary observer Percival Lowell called "revelation peeps." But a video recording captures an entire observing session, preserving those fleeting lucid moments like insects caught in amber.
Unlike 35-mm single-lens reflex (SLR) cameras, only a handful of the most expensive camcorders are equipped with removable lenses that would allow easy attachment to a telescope (using special adapters). Camcorders with permanent lenses require you to use what's called the afocal system. Here's how it works. The rays of light from a very distant object emerge from a telescope's eyepiece in parallel bundles. You bring this parallel light to focus on the camcorder's CCD by holding the camera's lens up to the telescope eyepiece. It's important to first have the telescope accurately focused, and this can be done by eye as long as you either have 20/20 vision or wear glasses that correct any near-or farsightedness to 20/20.
Sound complicated? Don't worry: most people find that focusing a telescope for afocal work is easy, especially since the real-time video image is visible in the camera’s viewfinder.