For those starting out in astro imaging with digital cameras, the first and most obvious target is
the Moon. It offers bright, sunlit scenery with a wealth of surface detail. Alan Adler took this close-up of the 85-kilometer-wide crater Tycho (near the bottom, with a central peak) and the Straight Wall (at upper left) with a
Nikon Coolpix 950. He attached the camera to his 8-inch f/6 Newtonian reflector fitted with a 10.5-millimeter eyepiece.
"Nothing is permanent except change," said the Greek philosopher Heraclitus. Anyone who follows the rapidly evolving digital-imaging world has to agree. Consumer-level digital cameras are becoming ever more powerful, small (if you want), and cheap. They have replaced film cameras as the tool of choice for the snapshooting public. But how good are they for astronomical imaging?
Film still surpasses all but the highest-end digital cameras for resolution and color accuracy. And, unlike dedicated astronomical CCD cameras that use cooled chips, the sensors in consumer cameras generate objectionable "noise" during long exposures, so their useful exposure times are generally limited to a matter of seconds. This is fine for bright subjects such as the Moon and planets, but too short for the deep sky — though you can beat the problem by taking many short exposures and digitally stacking them. Digital cameras generally need a computer to manipulate and print images, but the technology is evolving rapidly, and photo printers that work without a computer are now mass-market items.
Of course, the advantages of going digital are many. You get instant results and can adjust what you do accordingly — no waiting for pictures to come back from the photo lab. You can shoot all you want and throw all but the best pictures away without worrying about film and processing costs. The camera's memory can probably hold many more images than a roll of film.
Planets are also prime targets for digital cameras. Edwin Aguirre obtained this view of Venus with a Coolpix 990 coupled to the 12-mm eyepiece of his 8-inch f/10
Meade Schmidt-Cassegrain telescope.
Since the camera’s output is already digital, the images are ready for computer processing with programs such as
Adobe Photoshop, which can correct color imbalances, optimize brightness levels, dynamic range, contrast, and color saturation, and enhance image quality by stacking exposures. You can create a wide-field mosaic by stitching together adjoining frames. The images are Internet-ready — you can e-mail them or share them on the Web. They can be easier to sort and organize and take up less storage space than photo albums or shoeboxes.
Digital cameras are versatile — they can be used to digitize prints and 35-millimeter slides by recopying them. They can also be coupled a spotting scope for wildlife photography. The price of high-resolution cameras is constantly dropping. All these features make digital cameras very attractive for astro imaging. If you already have one, you should certainly see what it can do.
