Film Versus Digital

Film isn't dead yet. In fact, piggyback photography is one area of the hobby where film still performs very well, producing first-class results. So if you've invested heavily in film cameras, use them! Film has the resolution and velvety smoothness for this type of photography that general-purpose consumer digicams can't yet quite match.

That said, for piggyback shooting many films produce disappointing results. During a 5- to 20-minute exposure most films pick up lots of stars but exhibit an objectionable greenish cast. They also fail to record the glowing red nebulas that make wide-field Milky Way scenes so attractive. Why? Because manufacturers purposely block films' red sensitivity to make them more suitable for taking people portraits. As of early 2005, the two best color films in the market for piggyback shooting were both slide films: Kodak's Ektachrome E200 Pro and Fuji's Provia 400F.

The film camera of choice is the traditional 35-mm SLR (single-lens reflex) model. If you've purchased such a camera in the last few years, chances are it uses battery power to keep the shutter open. Even a couple of 15-minute exposures in the cold night air can quickly drain the battery, shutting down the camera. In the past, astrophotographers opted for low-cost, no-frills SLRs with mechanical shutters that worked without batteries (for sky shooting you don't need the autoexposure and autofocus features). Classic mechanical models such as the Pentax K1000, Canon F-1, Nikon F2, Minolta SRT-101, and Olympus OM-1 are still available at used-camera stores and through online auctions such as eBay.

On the other hand, digicams are taking over just about every sector of celestial imaging. For piggyback photography, the best choices are today's digital SLRs. These "prosumer" cameras offer 6 to 11 million pixels (megapixels) of resolution and inter-changeable lenses, usually the same lenses that fit on older film SLRs. (Most compact point-and-shoot digicams, the kind with nonremovable lenses, generate too much electronic noise during exposures lasting more than a minute.) While they depend on batteries, digital SLRs can deliver one to two hours of long-exposure shooting before you need to recharge the battery.

Film die-hards scoff at digital SLRs — until they see the results appear on the camera's built-in LCD viewing screen as soon as the exposure is completed. Then they sell off their aging film gear. I know I did! Digicams are wonderful for on-the-spot checking of the framing, focusing, exposure time, and tracking. A lot can go wrong during even a 5-minute exposure. Having instant feedback allows instant fixes, thereby improving your best-to-blooper ratio. Admittedly, digital SLRs are still pricey (starting at $700 to $1,000), but their cost has been coming down steadily.