Capturing celestial crinoline

When thin clouds or tiny airborne particles wash over the Sun or Moon in the sky, a colorful phenomenon called the atmospheric corona may encircle these bodies like a crinoline skirt. The spectacle consists of two parts: a bright glow (known as the aureole) with a smoggy orange fringe centered on the object, and a series of fainter colored rings (graduating from blue on the inside to red on the outside) surrounding the aureole. You can photograph both with DSLR or manual cameras. Here’s how.

Capture the rings
The Sun will produce the brightest and most colorful ring displays, but don’t shoot directly at its face. Plan ahead and use a nearby terrestrial structure, such as a rooftop or streetlight, to block the disk.

This photo of the atmospheric corona around the Moon is a composite of two exposures: A 3/10-second one with a 160mm lens at f/2.8 and an ISO of 400, and a 1/1,600-second one that shows details of the Moon’s surface. An occulting object is not necessary to image the Moon’s atmospheric corona, although the author partially used one here. All photos: Stephen James O’Meara

Typical coronal ring displays reach only a few degrees in apparent radius, and many are short-lived. So have your camera preset and ready to shoot. I suggest starting with a 50mm lens.

Prepare the camera by setting its mode to manual and the aperture to f/16. Now, apply the “blue-sky (f/16) rule” to fix the shutter speed: 1/ISO. So, if the ISO is 100, dial the camera’s shutter speed to 1/100 second; for an ISO of 200, set it to 1/200 second, and so on. Finally, focus to infinity, then turn the lens focus mode switch to manual.

A colorful interference pattern known as an atmospheric corona can result when light from the Sun or Moon passes around the edges of tiny water droplets, airborne particles, or needle-like ice crystals. It consists of a bright inner aureole and a series of concentric, colorful rings. Photographing one around the Sun requires blocking out the solar disk with a terrestrial object, like a rooftop.

After taking your first shot, review the image on the camera’s viewing screen and make fine adjustments. If the corona’s colors appear washed out, increase the f/stop or decrease the ISO or the shutter speed; if the image is too dim, do the opposite. If the corona appears too small, switch the 50mm lens for a telephoto and try the same settings. Use wider lenses to create scenic shots.

Imaging lunar coronae requires mounting the camera on a tripod and employing either the camera’s self-timer or a remote to release the shutter. Full (or near Full) Moons make the best photos. Start with a 50mm lens set at f/1.8 or faster and an ISO of 200 or 400 (your choice). Then take a series of exposures ranging roughly from 0.5 to 10 seconds (or longer depending on the intensity of the display).

To capture the Venus aureole with an artistic twist, the author used a wide-angle lens to shoot in the deep twilight. He then combined it with a telephoto shot of Venus to create the composite image seen here.

Because the Moon will appear washed out in these long exposures, you could also add a short exposure — for instance, 1/800 second at f/2.8 and ISO 200 for a Full Moon — that you can later incorporate into a composite image in Photoshop.

The Venus aureole
Venus is also bright enough to produce an aureole visible to the unaided eye. A time exposure will enhance the view, revealing a soft aqua inner glow collared by a warm orange ring. It’s easiest to capture the Venus aureole with an f/2.8 or faster telephoto lens (100mm to 200mm). As with the Moon, mount your DSLR camera on a tripod and use a self-timer or remote. Set the ISO to 400 and take a series of 3-second exposures while varying the f/stop between f/2.8 and f/5.6. The higher f/stops will create a beautiful ray pattern around Venus. You can combine the images afterward.

As always, let me know how you do at someara@interpac.net.

Up Next