Tips for Imaging a Partial Solar Eclipse

The advancing Moon takes a bite out of the Sun in this image taken early during the partial solar eclipse of May 10, 1994. Sky & Telescope's Rick Fienberg captured this view from Ogunquit, Maine, using an 8-inch f/10 Schmidt-Cassegrain telescope and a metal-on-glass solar filter.

Here are several simple tips that will help you succeed at capturing a partial solar eclipse on film:

  • To show the Sun's disk reasonably large, you need a lens or telescope with a focal length between 500 and 2,000 millimeters. This means you also need a firm tripod or mounting.
  • Use a visually safe solar filter over the front of the camera lens or telescope. (Check the article "Solar Filter Safety" for details.) Special solar photographic filters, designed to pass more of the Sun's light than visual solar filters, are okay only if used with caution.
  • Do a dry run on the uneclipsed Sun at least a couple of weeks beforehand. Begin by letting the camera's light meter choose the exposure. Then try a variety of other exposures on either side of it. Keep notes and see which comes out best.
  • If you're near the path of totality, the Sun will become very thin. When this happens, increase the exposure — both for esthetic effect and to compensate for the fact that the Sun's surface brightness is less near its limb.
  • If the Sun nearly fills the frame, focus to make the solar limb look sharp where it will actually fall on the film, near the frame's edges; don't move it to the center to focus on. Schmidt-Cassegrain telescopes in particular suffer from field curvature that makes the edge focus slightly differently than the center.
  • To reduce vibration, work the shutter button with a long cable release, or use the camera's delay timer. Lock the viewfinder mirror up beforehand if possible.

  • Don't forget to take a picture of the uneclipsed Sun at the start of your series to dramatize the change when the eclipse begins.

    A Wide-Angle Eclipse Sequence

    On a single piece of film, Akira Fujii acquired this striking sequence of the February 16, 1999, annular eclipse over Western Australia.
    Close-ups of the Sun's notched disk are easy to take through a filtered telescope, but a wide-angle sequence of images can be spectacular. Each solar disk should be exposed with the filter in place, of course. But you must remove this filter to expose the foreground scene and place the solar images in a deep blue sky. Be sure to underexpose the sky by one or two f/stops so the solar disks will stand out prominently in the final image.

    Astrophotographers of one school insist that the camera be left undisturbed on its tripod, with the same lens in place, for each image throughout the event. That way all elements of the scene are scientifically recorded in their proper, relative places; to do anything else would be "cheating." During an eclipse the Sun moves across the sky by its own diameter every 2 minutes or so, so an interval longer than this is needed to keep the images from overlapping (many people like to use a 5-minute interval). The foreground scene can be exposed earlier or later in the day when the uneclipsed Sun is well outside the frame.

    Other imaging enthusiasts prefer to leave the compositing until later — a necessity if your film or digital camera can't take multiple exposures. You can then select a foreground to your liking and plan the eclipse sequence for dramatic effect. One idea is to take the solar images through a normal or telephoto lens, arranging them along a shorter arc of sky than they would traverse in real life. The possibilities are endless for amateurs willing to let their imaginations run wild.

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