Introduction

Photographing an eclipse of the Sun is fun and easy. However, you will need to use a special Solar Filter to protect your eyes and your camera.

A solar eclipse occurs whenever the Moon's shadow falls on the Earth. This can only happen during New Moon when the Moon passes between the Sun and Earth. Although there is a New Moon every 29 1/2 days, there are usually only 2 or 3 solar eclipses each year. That's because the Moon's orbit is tipped 5 degrees to Earth's so the Moon's shadow misses Earth during most New Moons. (see: Solar Eclipses For Beginners)

Watching and photographing an eclipse of the Sun is a relaxing activity since it progresses at a leisurely pace. The eclipse begins as a small notch slowly appears along one edge of the Sun. During the next hour, the Moon gradually covers more and more of the Sun's bright disk. You'll need a Solar Filter to both view and photograph the partial phases. If the eclipse is an annular one, the last remaining minutes of the partial phases can be quite dramatic and beautiful. The crescent Sun grows thinner as it extends more that half way around the Moon's black disk. When the tips of the crescent horns connect with each other, the Moon's entire disk is seen in silhouette against the Sun. This is the amazing annular phase, sometimes referedto as the "ring of fire".

Solar Filters

Telescopes, camera lenses, and binoculars offer the possibility of seeing a magnified view of the eclipse. But this can only be done by using a special filter designed for viewing the Sun. Such filters fit snuggly over the FRONT END of the telescope or lens and permit just a tiny fraction of the Sun's light to pass through.

Solar filters for telescopes, camera lenses, and binoculars are available from a number of companies in the list below. Additional filter sources can be found through the American Astronomical Society.

These filters are essential for safely viewing both the PARTIAL and ANNULAR phases of an eclipse. No portion of this type of solar eclipse is safe to view without using a solar filter.

Visit Safe Solar Eclipse Viewing for more information.

Safe Eclipse Glasses from American Paper Optics (click here)

Cameras

Over the past decade or so, digital cameras have completely replace film cameras in virtually all aspects of photography. Solar eclipses can be captured easily with all types of digital cameras. The simpler Point and Shoot cameras have a non-interchangable lens with a single focal length. Better models are equipt with a 3x or larger zoom lens. The most versatile (and expensive) cameras are the DSLR (digital single lens reflex) and the ILMC (interchangeable-lens mirrorless camera). These cameras allow you to replace the kit lens with any number of other lenses from wide angle to super telephoto. You can even connect a DSLR or ILMC directly to a telescope so that the Sun fills the entire frame. No matter what kind of camera you own, one or more of the following techniques can be used be used to shoot a solar eclipse.

For simplicity, we will refer to both DSLRs and ILMCs as DSLRs. But all comments refer to both types of cameras.

Lenses and Image Sizes

A solar eclipse may be safely photographed provided that certain precautions are followed. Almost any kind of camera can be used to capture this rare event; however, a lens with a fairly long focal length is recommended to produce as large an image of the Sun as possible. A standard 18mm lens on a DSLR yields a minuscule image of the Sun, while a 200mm telephoto or zoom produces an image four times larger. A better choice would be one of the small, compact catadioptic or mirror lenses that have become widely available in the past decades. The focal length of 500mm is most common among such mirror lenses and yields a great image scale for capturing solar eclipses.

The sensor size of most DSLRs falls into on of two categories. The Full Frame Sensor (measuring 24 x 36 mm) is used in professional or upper end DSLR cameras. The Crop Sensor (measuring 16 x 24 mm [Nikon] or 15 x 22 mm [Canon]) is used in the less expensive consumer DSLRs. Either category can take excellent eclipse images, but the sensor size plays a determining roll in the apparent size of the Sun as seen with various focal length lenses.

As a general rule of thumb, the relative size of the Sun’s image appears 1.5 times larger in crop sensor DSLR compared to the image in a full sensor DSLR when using the same focal length lens. For example, a 500mm lens on a full frame sensor DSLR produces the same relative image size as a 330mm lens on a crop sensor DSLR (see diagram above).

The following table gives the field of view (in degrees) for a various focal length lenses. Note that crop sensor cameras have a smaller field of view than full frame cameras for any one focal length lens. For reference, the Sun's (and Moon's) apparet diameter is about 0.5°.

If full disk photography of partial phases of the eclipse is planned, the focal length of the optics must not exceed 2500mm on a full frame DSLR (1700mm on a crop sensor DSLR). Longer focal lengths permit photography of only a magnified portion of the Sun’s disk. The figure below shows the apparent size of the Sun during mid-annularity in both full frame and crop sensor formats for a range of lens focal lengths.

Based on the above diagram and table, the optimum focal length range for photographing an annular solar eclipse is:

1. Full Frame DSLR - 750 mm to 1500 mm
2. Crop Sensor DSLR - 500 mm to 1000 mm

These are unusually long focal lengths for most photographers but do not be discouraged. Resonable results can be achieved with shorter focal lengths and cropping the images in post processing.

It is also advisable to turn off autofocus because it is not reliable under these conditions; focus the camera manually instead. Use sunspots and the horns of the solar crescent to refine your focus as annularity approaches. A piece of masking tape or gaffers tape around the focusing ring will help ensure it it is not changed accidentally. Preparations should be made for adequate battery power and space on the memory card.

Sturdy Tripod

A sturdy tripod is needed to support a telescope or long telephoto lens while photographing the eclipse. The Sun slowly moves across the sky from east to west (moving its own apparent diameter every two minutes), so you will need to recenter it in your camera every few minutes. This can be done with tripod having an adjustable pan head. Some tripod manufacturers offer a head with slow motion knobs to make fine adjustments and these work well for eclipse photography. For example, the Manfrotto 410 3-Way, Geared Head is one the author has used for many years.

An even better solution is to use a star tracker. This is a motorized device that rotates the camera/lens/telescope to counteract Earth's rotation, and thereby track the Sun, Moon, and stars. Most star trackers can be mounted on a sturdy camera tripod, replacing the original head. A good review article is AstroBackyard's Choosing a Star Tracker for Astrophotography. PetaPixel offers a more recent article on Best Star Trackers in 2023.

A star tracker must be set up with its polar axis pointed towards Polaris (the North Star) in order to work properly. To do this in the daytime, see the Sky & Telescope article Daylight Polar Alignment Made Easy.

2005 Annular Eclipse Sequence
This seven image sequence captures the essential stages of the eclipse.
Annular Solar Eclipse of 2005 Oct 03 (Carrascosa del Campo, SPAIN)
(click to see more photos)

Partial Phases and Correct Exposure

A solar filter must be used on the lens throughout the partial phases for both photography and safe viewing. Such filters are most easily obtained through manufacturers and dealers listed in Sky & Telescope and Astronomy magazines. The American Astronomical Society has also created a list of Sources of Solar Filters These filters typically attenuate the Sun’s visible and infrared energy by a factor of 100,000. The actual filter factor and choice of ISO speed, however, will play critical roles in determining the correct photographic exposure.

Almost any ISO can be used because the Sun gives off abundant light. An ISO of 200 is an good for eclipse photography. The easiest method for determining the correct exposure is use the camera's built in spot meter mode on the uneclipsed Sun. With a solar filter on your lens or telescope, put the camera into manual exposure mode and adjust settings while metering on the Sun. Take a shot and examine it using the camera's histogram display - a good exposure should peak in the middle of the histogram range. If it does not, make any necessary adjustments to the exposure. If your camera does not have spot meter mode, you can determine the best exposure through trial-and-error. In manual exposure mode (and using a solar filter), shoot a series of exposures of the mid-day Sun at a fixed aperture (f/8 to f/16) using every shutter speed from 1/1000s to 1/30s. Select the best exposure using the camera's histogram display.

Make note of the best exposure since you will use it on eclipse day. The Sun’s surface brightness remains constant throughout the eclipse, so no exposure compensation is needed except for the narrow crescent phases and annularity, which require one or two more stops due to solar limb darkening. Bracketing by several stops is also necessary if haze or clouds interfere on eclipse day.

Always use the camera RAW file format to get the best quality images. Smaller JPEG files can be made from RAW files after the eclipse is over.

2005 Annular Eclipse Matrix
This 25 image sequence captures the entire eclipse from start to finish.
Annular Solar Eclipse of 2005 Oct 03 (Carrascosa del Campo, SPAIN)
(click to see more photos)

Timed Exposures

From start to finish, an annular eclipse lasts about two and a half hours. Many eclipse photographers choose to shoot a sequence of images spanning the entire eclipse. But it can be monotonous to sit next to a camera shooting an image every few minutes.

Fortunately, there is an easy solution. Many cameras have a built in interval timer. The start time, interval between shots, and the number of shots can all be set in advance. The photographer only needs to keep the telescope or camera lens trained on the Sun during the eclipse. Battery operated star trackers work well in this regard.

If the camera does not have a built in interval timer, there are inexpensive external timers available from camera shops and Amazon. The typical interval between each image is one to five minutes. After the eclipse, the images can be combined with editing software into a linear sequence or a two dimensional matrix that illustrates the entire eclipse in one composition.

An excellent resource on eclipse photography and processing is the eBook written by Alan Dyer: How To Photograph Solar Eclipses.