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How to Put the Astro in Photographer
Many people ask how my astrophotographs were produced.
They also ask what kinds of astrophotographs they can create.
I’ll try to answer both of these questions here.
How Astrophotographers Do It
Firstly, you can count the number of full-time “professional astrophotographers” on Earth with the fingers of one hand. The vast majority of fine-art astrophotographs are created by dedicated amateur artists like myself. (Professional astronomers are interested in data, not pretty pictures). My specialty is expansive views of nebulae (faint clouds of gas) that cover a few degrees of sky. Medium format film is still the best method for that.For optimal photography, a clear dark location is required. Unfortunately light pollution from humanity’s nighttime lighting is increasingly stealing the night skies from us. It is also important that the moon be near its darkest phase, because its light, too, fogs film. In New England where I live, the weather is cloudy and unpredictable, which makes it a difficult location for astrophotographers. If the weather is favorable, I am obliged to photograph until dawn; an average of three nights per month may be usable. Mainly I use locations in New Hampshire, where few cars pass at night. A couple times per year I bring the equipment to highly favorable locations in the Southwest U.S.
I need to pack thousands of dollars of delicate equipment into my hatchback for the trip North. I like to arrive before sunset, because the setup takes a couple of hours. I use a portable, rigid aluminum pier to hold a massive mount head that tracks the stars. On the head goes the telescope (essentially a 900mm f/7 APO lens). On the telescope goes a Pentax 6x7 camera. Then a bunch of other supporting optics and electronics are attached. Then I go through an involved process of drift alignment. By carefully watching the slightest drift of stars in the field of view, I align the system to within arc seconds of the true North pole. The ideal situation is a permanent observatory in a superb location; perhaps someday I'll have that.
In advance, I use software to create custom printed maps of the sky that portray the exact composition of the shot. This is important, since I usually cannot see the object I’m shooting in the camera’s view finder, only patterns of stars. Focusing the camera precisely is an exact science and requires custom tools and techniques. Finally the shutter can be opened, while the electronics ensure that the system is precisely locked onto the target. A typical exposure is 60 minutes. For the best resulting images, I'll take multiple exposures of the exact same field of view, to be digitally combined (stacked) later for increased clarity.
If I’m fortunate, I'll have an exposed roll of 120 film for one night’s work. The film may be gas-hypersensitized ISO 400 professional color print film or perhaps plain old Kodak E200 slide film. The film can be developed normally by a lab.
Now the second half of the work can begin. The film frames are scanned on a medium format scanner into digital format, yielding up to 200MB of data per frame. The frames are stacked (if there are multiples) using special software. Adobe Photoshop is used to curve the images (establish pleasing contrast and color saturation). I may need to use anti-vignetting techniques or special kinds of blurring or sharpening. I take care to make sure that the resulting colors are as true to life as possible.
These images can then be uploaded to my web site, printed, or emailed to a magazine or to a stock photo agency.
How Can You Get Started?
You can take beautiful star trail astrophotographs with equipment that you may already have. Again, the best images require a dark, clear, moonless location. Set up the film-camera (e.g. 35mm SLR) on a tripod, focus at infinity, and open the shutter for at least an hour. As in terrestrial photography, you want to use fine-grain (slow) film for best quality. On ISO 200 film (Kodak E200 is excellent), you would typically use f/5.6. A lens shade helps keep away stray light and dew. If the location is dewy, you may need to use a dew remover. Including trees, buildings, etc. usually livens up the composition.If you have the means to get the film frames expertly scanned and can manipulate them in Photoshop, you will get the best results. By the way, virtually all digital cameras are unsuitable for shooting star trails.
After you master star trails, the next logical step would be an investment in a motorized equatorial mount for wide-field astrophotography of constellations and the Milky Way. Will you be ready when the next great comet comes along?
