|Single frames capturing portions of the Milky Way are beautiful, but a panorama displaying the galaxy edge to edge is particularly dramatic. This takes some technical mastery using tools like the Really Right Stuff PG-02 Pro Omni-Pivot Package (reallyrightstuff.com) shown below right. Glenn Randall uses this setup for precise control over the horizontal and vertical movements and PTGui software (PTGui.com) for stitching the images together. The final panorama presents the Milky Way's full spectacular arch.|
Of all the wonders of the night sky, the most spectacular subject for photographers who lack a telescope is surely the Milky Way. The only hardware required is a sturdy tripod, a relatively new DSLR with good high-ISO capabilities and a wide-angle lens, the faster, the better. This article will provide the other key ingredient: the information you need to make your own spectacular photos of the Milky Way.
Let's start with a refresher on your college astronomy class. We live in the Milky Way galaxy, which is shaped like a plate, not a sphere. Our solar system lies partway between the center and the rim. The Milky Way is the band of light formed by billions of very distant stars that you see as you look along the galactic plane. You can see the Milky Way every clear, moonless night of the year, but it's not equally bright in all directions. If you look away from the center of the galaxy, you're looking through a region with relatively few stars. If you look toward the center of the galaxy, however, your line of sight leads past many more stars, so the Milky Way is much brighter and has more interesting structure.
The center of our galaxy and the most photogenic part of the Milky Way lie in the direction of the constellation Sagittarius. Like any celestial object, Sagittarius appears to rise and set as the Earth rotates. Sagittarius is most prominent in late spring, summer and early fall, and isn't visible in winter because it's only above the horizon during the day.
Even the brightest part of the Milky Way is relatively dim. Get as far away from city lights as possible, and shoot on a clear, moonless night during the interval between astronomical dusk and astronomical dawn, when the sky is as dark as it will get. Programs like The Photographer's Ephemeris (photoephemeris.com, free for desktop computers) provide moonrise and moonset times, and the times of astronomical dusk and dawn.
The sky is always brightest near the horizon. It gets darker as you look higher into the sky. That's true at night, as well as during the day. To make the Milky Way stand out against a dark sky, shoot when Sagittarius is as high in the sky as possible. Sagittarius reaches its highest elevation above the horizon, an altitude of 23º as seen from the latitude of Colorado, when it's due south. As with any landscape, the best Milky Way photographs include more than sky. When planning your shoot, therefore, think about compositions in which you're looking roughly south at something interesting. Arches, sandstone towers and dramatic peaks make good land elements. You don't need to worry about foregrounds; the depth of field is so shallow at the wide-open aperture you'll be using that you won't want anything in the frame closer than 20 or 30 feet.
Carina Software's SkyGazer program (carinasoft.com, $29 download) can tell you when Sagittarius will rise and set, and when it will reach its maximum altitude. After installing the software, open the Window drop-down menu and be sure Time Panel, Location Panel, Display Panel, Info Panel and Sky Chart are checked. Then choose Display > Milky Way, and be sure Show Milky Way and Photorealistic Milky Way are checked. Finally, open the Center drop-down menu, click Constellations, then choose Sagittarius. You can adjust the date and time in the Time Panel. SkyGazer then will display a view of the sky, including major stars, Sagittarius and the Milky Way. If Sagittarius isn't initially visible, click Center in the Info panel to display it.
Once you arrive at your chosen location, you face the next two challenges: focusing and composing at night. Auto-focus is useless; turn it off completely so you don't accidentally trigger it. Nor can you simply set the lens to the infinity mark. That's not sharp enough, either. Instead, point the camera toward a bright star, set the lens to infinity to get close to proper focus, engage Live View, magnify the view to 10x and focus manually on a star. You may need to disable exposure simulation in your Live View menu to actually see a star. Composition is a matter of guess and check, since you can't see the Milky Way through the viewfinder. Level the camera left to right with a hot-shoe level, point it in approximately the right direction and shoot a test frame. Adjust, as needed, and try again. I use the red LEDs on my headlamp when working at night to let my eyes adapt to the dark as much as possible.
A good starting-point exposure for the Milky Way on a moonless night is 30 seconds, ƒ/2.8, ISO 6400. But here's the catch: You need a 16mm lens on a full-frame camera to use such a long exposure without the stars forming streaks due to the rotation of the Earth. The shorter the focal length, the longer the exposure you can use before the stars move noticeably. Refer to the chart above to determine the longest non-streaking exposure you can use with different focal-length lenses.
Holding detail in the land can be difficult. You can get some detail in the landscape from starlight, particularly if there's lots of snow on the ground. To obtain more detail, shoot just before astronomical dusk or just after astronomical dawn. The full moon will provide great detail in the land, but it will wash out the stars. A good compromise is to shoot when the moon is 15% to 30% illuminated and providing texturing sidelight to the scene. Avoid backlighting. All of these approaches create a trade-off: brighter land means a dimmer Milky Way, and vice versa. You can try shooting at ISOs above 6400 if your camera offers them, but the noise may be intolerable. A better, but more laborious solution is to shoot a frame with a shutter speed long enough to record detail in the land, ignoring the resulting star trails, then combine the correctly exposed land with the correctly exposed sharp stars from a frame with a shorter exposure. The image on your LCD probably will give you a false impression of how much land detail you've actually captured. Go into your menus and turn down the LCD's brightness, and be sure to check your histogram.
If you're shooting with a daylight white balance, you may be startled by the yellow-green color of the sky in your first Milky Way shots. Even on the darkest night, the sky is never completely black. Instead, it exhibits a faint greenish glow caused by a variety of processes high in the atmosphere. We don't see the night sky as green, of course; in fact, we don't really see color at night at all. I usually set the color temperature to about 3200 degrees K in Lightroom to restore the blue-black color we imagine the night sky to be.
Milky Way Panoramas
Single-frame photographs of the Milky Way are beautiful, but the Milky Way offers other photographic possibilities, as well. Look closely with dark-adapted eyes, and you'll see that the Milky Way forms a gigantic arch in the sky that extends from horizon to horizon. This arch is far too large, in an angular sense, to be captured in a single frame, even with the widest rectilinear (non-fish-eye) lens. The best way to shoot it is as a stitched panorama with a multi-row panorama head.
Shooting a Milky Way panorama is easiest in the spring just after Sagittarius has risen high enough to be above any foreground mountains. At that time of year, the Milky Way arch is relatively compact. The high point of the arch will be due east and considerably lower in the sky when the sky is fully dark and Sagittarius is in the right position than it will be later in the summer. For example, the top of the arch is roughly 50º above the eastern horizon on April 1 at the ideal time of night, but closer to 90º on September 1.
|Camera Settings For The Milky Way|
|This chart assumes you're using a full-frame camera such as a Canon EOS 5D Mark III or Nikon D800. If you're using a camera with a "sub-full-frame" or APS-C sensor, multiply the focal length printed on the lens by the appropriate "crop factor" or "multiplication factor," then use the result as the focal length for the purpose of this chart. For example, if you're using a 16mm lens on a camera with a 1.5 crop factor, multiply 16 by 1.5 to get 24. The longest exposure you can make with that lens without visible star motion is 24 seconds. Note that this chart assumes you're viewing a print made at normal resolution for a high-quality print (file resolution of 240 to 300 ppi). If you zoom in to 100% on your monitor, you'll see some very short star trails.|
|Focal Length||Angle of view (horizontal dimension in landscape mode)||Angle of view (vertical dimension in landscape mode)||Maximum shutter speed to avoid visible star motion in a print|
My favorite hardware for multi-row panoramas of the Milky Way is a Canon EOS 5D Mark III, a Canon 50mm ƒ/1.4 lens and a Really Right Stuff multi-row panorama head (the PG-02 Pro Omni-Pivot Package, $895). The RRS pano head lets me rotate the camera in precise increments both horizontally and vertically. Photoshop can't handle stitching of this complexity, so I use PTGui, which has two major advantages over Photoshop. The first is that PTGui lets you define the grid in which the individual frames will be placed. You can, for example, tell PTGui that you shot four rows of 10 images each with a 20º pan between images in each row and a 30º pitch in between rows. This information allows PTGui to create a rough layout of the images. PTGui's second advantage is that you can add control points manually. Control points, which always come in pairs, mark the identical point in the overlapping portions of two adjacent frames. As with any panorama, be sure you use manual exposure, focus, white balance and ISO so that the component images will stitch together seamlessly.
Don't let the technical details of a complex Milky Way shoot overwhelm the experience of being there. Take a moment during the shoot to turn off your headlamp and soak in the beauty of the night sky. It's the best way I know to truly appreciate the immensity of our universe.
Go to www.glennrandall.com to see more of Glenn Randall's work, sign up for his monthly newsletter, read his blog and learn about workshops.