Imaging a Solar Eclipse

Total solar eclipse
Jonathan Kern and Wendy Carlos's composite of the Sun's gossamer corona approximates the view with the naked eye during the 1999 eclipse. Carlos digitally combined five scanned negatives with Adobe Photoshop. Four exposures were through Kern's custom-made radially graded filters — two by him from Rimnicu-Vilcea, Romania, with a 1,500-millimeter lens and Kodak PRO 400 PPF film (10 and 40 seconds) and two by Carlos from eastern Bucharest with a 1,200-mm lens and Fuji NPH 400 film (1 and 4 seconds). A fifth unfiltered 1/30-second image by Carlos was added for the lunar limb and prominences.
© Wendy Carlos & Jonathan Kern.

Nothing quite matches the experience of viewing a total eclipse of the Sun. Whether it's the black disk of the Moon set against the ghostly, pearly white corona, the solar prominences like pink rubies on the lunar limb, or the spectacular diamond-ring effect bursting forth, the image of an eclipse remains forever etched in a viewer's mind.

The human eye is superb in its ability to discern and resolve a wide range of brightnesses and details during an eclipse — from the diaphanous, faint wisps of the outer corona to the fine, hairlike structures in brilliant prominences. However, with the advent of high-speed, ultrafine-grain film and high-resolution video cameras, it's an ethereal scene almost anyone can capture using only modest equipment.

Choosing the Right Equipment

The type of camera lens you should use depends mainly on what you want to record. For wide-angle shots of the sky with a film camera, a standard 50-millimeter lens is all you need. Although it gives only a minuscule (0.5 mm in diameter) image of the Sun on film, it is well suited to capturing the surrounding sky with Venus, Mercury, and possibly a few bright stars. For dramatic effect, try to include foreground objects in the scene. Fisheye lenses can capture the whole sky and are especially good for documenting the approach and retreat of the umbra (lunar shadow) and the 360° sunset — twilight colors that ring the entire horizon.

Totality
The adage “A picture is worth a thousand words” is never truer than with an image of the totally eclipsed Sun. For sheer beauty and magnificence, perhaps no celestial phenomena can compare with it. Sky & Telescope associate editor Edwin Aguirre captured this sequence showing 2nd contact (left), totality, and 3rd contact (right) during the July 11, 1991, total eclipse in Baja California, Mexico, on Kodachrome 200 slide film with a tripod-mounted 4-inch f/10 Schmidt-Cassegrain reflector.

If you want to show the Sun's disk reasonably large on film, however, you need a telephoto lens or telescope with a focal length between 500 and 2,000 mm, preferably on a steady mount. A 1,000-mm lens yields a solar image 9.2 mm across and is perfect for framing the outer corona, which can easily extend more than ½° from the Sun's limb.

For close-up shots of the eclipse's partial phases, Baily's Beads, diamond rings, chromosphere, solar prominences, and inner corona, you'll want a lens or telescope with about 2,000 mm focal length. This produces a solar image approximately 18 mm in diameter, which nearly fills the frame of a standard 35-mm camera. (Focal lengths longer than 2,600 mm will not show the entire solar disk.) You can boost the effective focal length of lenses with a 2x or 3x teleconverter. For any particular focal length, the diameter of the Sun's image is roughly equal to focal length divided by 110.

Veteran eclipse photographers often test their equipment on the Moon around the time it's full. Not only is the Moon's apparent size about the same as the Sun's, but it has roughly the same total brightness as the corona. A series of exposures, made along with careful notes, can reveal potential problems with focus and vibration, as well as internal reflections and vignetting in the lens.

If you plan to photograph the eclipse's partial phases, make sure you have a visually safe solar filter securely mounted on the front of the telephoto lens or telescope objective. Polarizing or photographic neutral-density filters are not safe for visual use. Be sure to test your setup on the midday Sun well ahead of the eclipse to determine the best exposure to use.

The Importance of Focusing

Diamond Ring
Johnny Horne of the Fayetteville Observer-Times captured this magnificent image of the 'diamond ring' during the total solar eclipse of February 26, 1998. A Sky & Telescope contributing photographer, Horne observed the event from the deck of Holland America Line's Statendam.

Don't let poor focus ruin your eclipse photographs. This is especially important when using telescopes and long telephoto lenses that do not have a fixed infinity setting. Most 35-mm cameras have optional magnifiers for the viewfinder, which aid with focusing. Once you achieve optimum focus, place a piece of adhesive tape across your lens's focus ring or telescope's focus knob to prevent it from accidentally being moved during the eclipse. The same technique also applies when setting zoom lenses, which can slip without warning, especially when aimed high in the sky.

For full-disk photography of the Sun, focus on the solar limb when the is image framed the way you want it — don't move the limb to the center of the field for focusing. Schmidt-Cassegrain telescopes in particular have curved focal planes that make the edge focus a little differently than the center. Be sure to recheck your focus as the eclipse progresses, since changing temperature can cause the focus to shift slightly.

Mountings

Deck of a cruise ship
Mobility is often essential for successfully observing a solar eclipse, especially when the weather prospects are poor. Cruise ships have the advantage of being able to maneuver to dodge clouds on eclipse day. Sky & Telescope associate editor Edwin Aguirre took this snapshot of the MS Veendam’s crowded foredeck during the February 1998 eclipse in the Caribbean Sea.

Whether you're traveling by land, sea, or air to your observing site, try to keep your mount as portable, light, and easy to assemble and operate as possible. Portability is especially essential if you need to relocate in a hurry to escape clouds.

If the Sun’s altitude will be high during the eclipse, make sure your camera tripod can be aimed this high. A pan head with slow-motion controls offers smooth guiding when you are manually tracking the Sun, which moves at about ¼° per minute across the sky.

To improve a tripod's stability, hang a jug of water or a duffel bag filled with sand under the center post. You can also wrap plastic bags of sand on each leg or set the tripod on rubberized footpads to dampen vibrations. The mirror slap in single-lens reflex (SLR) cameras can cause blurred images, especially in long exposures on slow film. To further minimize vibrations, work the shutter button with a long cable release. Lock the viewfinder mirror up beforehand if possible. Last, choose your site so it's shielded from direct breeze; erect a windbreak if needed.

Use Film or Go Digital?

Totality from Aruba
Japanese astro imager Shigemi Numazawa melds conventional photography with digital technology to obtain this highly detailed portrait of the February 1998 eclipse from Aruba. Numazawa made a series of exposures from 1/60 to 4 seconds long on Fujichrome Velvia 50 film with a Pentax 4-inch f/7 refractor and 2x teleconverter yielding an effective focal length of 1,400 mm at f/14. Using a technique he calls 'multiple-layer digital processing,' he digitized and composited nine exposures with Adobe Photoshop to produce this final image.

Selecting the best film for eclipse photography has never been easy, especially with the bewildering assortment of emulsions available today (Sky & Telescope: January 1999, page 143). In general, however, color-negative emulsions (those used for prints) offer greater exposure latitude; that is, they record features over a wider range of brightness with a single exposure than transparency (slide) films do. On the other hand, slides render rich, vibrant colors that are not vulnerable to variations that occur when one makes prints from negatives.

When choosing the film's speed (ISO rating) bear in mind that the faster the film, the shorter the exposure. Short exposures tend to minimize blurring due to vibrations, rolling of the ship (if you're at sea), and tracking errors. But fast films tend to be grainier than their slower counterparts.

There is nothing worse than running out of film in the middle of totality. During an eclipse of 2 minutes or longer, it's easy to use up a 36-exposure roll, especially if your camera has a motor drive. And nobody wants to waste precious seconds fumbling in the dark to change films! The best advice is to load a fresh roll in the minutes just before totality begins. Pace yourself and keep track of the number of exposures made. It's the quality that counts, not the quantity. It's better to have a few perfect corona shots than three dozen poor ones.

The Digital Alternative

Totality
Sky & Telescope senior editor Dennis di Cicco used a Nikon Coolpix 990 digital camera and a Meade ETX70 refractor to acquire this image of totality on June 21, 2001.

The current trend in still photography is toward digital cameras, which use a CCD chip instead of film for capturing images. A digital camera's resolution is often measured by the number of pixels in its image. The more pixels, the higher-resolution the image will be.

Digital cameras range from entry-level point-and-shoots costing $200 or so to studio cameras costing from $3,000 upward. The newest category on the mass market (near the middle of this price range) are digital SLR cameras, which look and feel like 35-mm SLRs and have detachable lenses.

Digital cameras typically use removable memory cards to store images. High-resolution pictures require more memory, so eclipse imagers must plan ahead in order not to run out of memory at a critical time.

Eclipse Videography

Video diamond ring
Using an 8-millimeter camcorder with a 200-mm zoom lens and piggybacked to a Celestron C5 telescope, Imelda Joson and Ron Hise captured this video image of the 1991 eclipse's diamond ring at second contact. Changing the lens's focal length and aperture (f/stop) emphasized various features of the event, with the longest focal length and smallest aperture best for recording the prominences and inner corona, the shortest and largest for the outer corona.

Nothing evokes memories of an eclipse better than a video. That's why more and more eclipse chasers are choosing camcorders as their primary recording medium. Camcorders offer instant gratification in the field unmatched by conventional photography. All of today's camcorders use CCD or MOS (metal-oxide semiconductor) detectors that have high sensitivity yet will not be harmed by brief exposures to direct sunlight.

The Hi-8 and S-VHS formats offer better resolution than the old 8-mm, VHS, or VHS-C formats. The compact size and light weight of 8-mm camcorders make them ideal for travel. There are dozens of models and prices to choose from, with features such as flip-out LCD viewfinders and image-stabilized optics.

All camcorders have zoom lenses, some with up to 32x optical and 330x (or more) "digital" magnification. Optical zoom is what matters, since it increases the image scale on the detector. (Digital zoom simply crops in on the center of the view, reducing resolution.) The easiest way to determine the approximate size of the Sun in your camcorder is to shoot the Moon, zooming in from lowest to highest power. If your camcorder doesn't have enough magnification, consider adding a teleconverter (2x or more) to the front of the lens. Or shoot through a telescope's eyepiece.

As with still cameras, you need a proper solar filter over your camcorder or scope when recording the partial phases. You can take 2- to 3-second clips every five minutes or so to produce a time-lapse sequence that compresses the hours-long partial phases into just minutes. High-end camcorders have manual controls for adjusting the gain, f/stop, and "shutter" speed so you don't overexpose the bright inner corona or cause blooming (streaking) of the image. Again, it's best to test your setup on the full Moon well in advance. On eclipse day, be sure to use a battery freshly charged at least a half hour before totality. Keep a spare one as backup.

The Digital Darkroom

Recording the corona's full range of brightnesses and details in a single view has been the Holy Grail of eclipse imagers. In the past astronomers have used different techniques, including special radially graded filters, to suppress the bright inner corona and capture the solar atmosphere's full shape and structure. They have also spent countless hours in the darkroom stacking negatives and using sophisticated dodging and masking techniques to bring out subtle coronal details.

Totality
This dramatic view of totality shows delicate streamers in the corona — the Sun's million-degree outer atmosphere — and several red jets of hydrogen gas peeking out from behind the silhouetted Moon. By merging and processing 16 exposures, 4 shot by Jonathan Kern using radial graded filters and 12 unfiltered images that she herself took, Wendy Carlos created a view of totality that faithfully reproduces how the eclipsed Sun actually appeared in the sky over her observing site at the Barn motel in Lusaka, Zambia, on June 21, 2001.
© Wendy Carlos & Jonathan Kern.

Such darkroom work is a thing of the past in the age of computers and image-processing software. Astrophotographers can now take a range of exposures, select the best ones, and use graphic-arts programs such as Adobe Photoshop to combine them into a single image (Sky & Telescope: January and July 1998, pages 117 and 50, respectively).

Each exposure is digitized and processed with an unsharp mask. With just a few mouse clicks, you can easily retouch any film defects (dust specks, scratches, or fingerprints) and adjust the image contrast, brightness, and hue. A half dozen or more images can be processed this way and then sequentially coadded to improve the image quality and produce a smooth composite, which can be printed on a high-quality photo printer or sent to a photo lab to produce prints or slides.

Helpful Tips

Based on my previous eclipse expeditions, here are some suggestions worth keeping in mind:

  • Use a pocket tape recorder to document your observations and reactions.
  • During the March 1988 eclipse in Mindanao, Philippines, the umbra was so dark it was difficult to read the camera's shutter dial. On the other hand, the July 1991 eclipse in Baja California was so bright it was possible to read a newspaper during totality! Be prepared and keep a small pocket flashlight handy.
  • When packing your things, put delicate equipment like cameras, telephotos, and camcorders in your carry-on baggage to ensure safe handling. Commercial airlines are now restricting the amount and size of carry-on baggage, so be sure to check with them or your travel agent to avoid problems during boarding.
  • New, more powerful security X-ray machines are in use at many airports. These can damage film. Even lead-lined film pouches are no longer impenetrable. So ask that your films be hand-inspected.
  • For safety, ask your photofinishing lab to leave your developed (slide) films uncut. You don't want the lab accidentally slicing your best shot in half because the separation between frames is difficult to see.

Final Thoughts

I know it's difficult, but take a few moments to leave your gear alone and enjoy totality with your unaided eyes or through binoculars. I've often heard tales of people so engrossed with their imaging that they missed seeing the eclipse visually. In all my eclipse chasing, I've always made it a point to catch (between exposures) good glimpses of the spectacle going on above me. No photograph or video can compare with the real thing.

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