Partial Solar Eclipse Photography: Comparing It With an Annular Eclipse

What a Partial Eclipse Looks Like

Through a certified solar filter, the partial phase begins as a small bite on one edge of the Sun. The Moon's dark limb moves steadily across the disk, and the uncovered part shrinks into a thin crescent before the eclipse ends. The change is gradual. Over most of the event, the difference between one frame and the next is small, so the sequence you record is what shows the progress.

The Moon's shadow never falls fully on your location during a partial eclipse. The sky does not darken noticeably, and the air does not cool in any way you would feel. The eclipse is visible across a wide region of Earth's day side, but your position within that region sets how much of the Sun is covered at the maximum point.

Your naked eye cannot safely judge the eclipse at any stage. Through a solar viewer that meets ISO 12312-2, you will see a dark notch or crescent cut into the Sun. Use this view to check that the eclipse is progressing as expected before you point a camera at the Sun.

The Dark Notch and the Crescent

Near the middle of the event, the uncovered region is usually the largest visible crescent, and the covered part looks like a dark notch against the bright disk. The shape depends on how much of the Sun the Moon hides at that point. A shallow partial eclipse produces a wide, bright crescent. A deep partial eclipse leaves only a narrow sliver. In both cases, the edge of the Moon is sharp against the Sun's bright surface, which makes it useful for practising focus.

How It Differs From an Annular Eclipse

In an annular eclipse, the Moon is at a distance from Earth that makes its apparent disk slightly smaller than the Sun's. When the Moon is centered on the Sun, a thin bright ring stays visible all around its edge. The ring is the visible part of the Sun for the whole time the centerline passes over you. The annular phase is therefore a central event, and it lasts only a few minutes at most at any location.

The partial eclipse has no ring. It is an off-center alignment, so the Moon covers one part of the disk and leaves the rest bright. Because of this, the partial eclipse can be seen from a much wider area, while the annular path is narrow. Your decision about where to observe depends on which event is happening.

Comparing the Two Events

Appearance

A partial eclipse shows a crescent or notch, and the Sun's disk stays uneven in brightness across the event. An annular eclipse shows a complete ring at its peak. In a photograph, the partial eclipse has a dark bite that moves across one side, while the annular eclipse has a symmetric bright halo with a dark center. The two images are easy to tell apart, which is one reason the comparison teaches useful habits. Partial eclipse images reward careful framing of the crescent. Annular images reward accurate centering of the Moon.

Difficulty and Timing

The partial eclipse is usually easier to find, because it covers a large region. You have more places to observe from and more time windows within the event. The difficulty is in holding a long sequence. The partial phase can last well over an hour, and you must take frames at regular intervals and keep the Sun in focus and in frame the whole time.

The annular eclipse is harder to reach. Its central phase is short, and the path is narrow. Your timing must be accurate, and you may need to travel. Once you are in position, however, the ring takes less frame-to-frame effort than the changing crescent. Photographers who plan for annular eclipses often prepare a single, precise sequence rather than a long run of frames.

Technique

Both events need a certified solar filter on the lens or telescope. A full-aperture filter must cover the front of the instrument, not the eyepiece, because light entering the instrument without filtration can damage the eye and the equipment. Both events also benefit from a solid mount, a clean focus, and short exposures, because the Sun is very bright. The main technical difference is the subject. The partial eclipse calls for patient tracking of a changing crescent. The annular eclipse calls for careful centering and, often, a brief set of exposures around the ring's peak.

What Each Teaches

A partial eclipse teaches you how the Moon's edge moves across the solar disk and how to plan an unattended sequence of frames. It also shows how quickly the Sun's light changes shape even when its overall brightness remains constant. An annular eclipse teaches you how the Moon's apparent size changes with its distance from Earth and how precise alignment must be for a ring to form. Studying both gives you a full picture of how the Sun and Moon line up over time.

Equipment for Solar Photography

Solar Filters

Use only filters that meet ISO 12312-2. For a camera lens, this usually means a filter film or a solid filter that fits the front of the lens and covers the full aperture. For a telescope, use a full-aperture filter at the front of the optical tube. Never use a filter that threads onto an eyepiece, a filter of unknown rating, or improvised materials such as exposed film, smoked glass or sunglasses. Inspect the filter before each session for scratches, pinholes or damage, and replace it if you find any.

Camera and Telescope Setups

A camera with a telephoto lens, or a telescope with a camera adapter, will record the partial eclipse well. The focal length determines how large the Sun appears in the frame. At about 1000 mm focal length, the Sun's image is roughly 9 mm across, so a crop may be needed to fill more of the frame. A 130 mm reflector or a refractor of similar size is a practical choice for many photographers. A smart telescope can also run a solar program if its manufacturer supports solar filtering, but confirm that the filter is certified before use.

Planning Around Your Local Sky

Check the date and time of the eclipse for your location using a planetarium program or a local astronomical almanac. The partial phase is visible across a wide region, but the Sun must be above your horizon during the part of the event you want to record. An eclipse that begins before sunrise or ends after sunset will show only part of its progress at your site.

The Sun's altitude changes with latitude and season. Observers at 35° N, 50° N and 35° S will see the Sun at different heights above the horizon at the same clock time. A higher Sun gives a steadier image and reduces the amount of atmosphere you look through. Observers in the Southern Hemisphere at 35° S will see the Sun in the northern part of the sky for the same season, so check the direction on your own site before you set up. The same applies to 50° N, where the Sun may sit lower during the cooler months.

In a suburban sky, the Sun's brightness means light pollution does not limit the partial eclipse. The main limits are haze, heat shimmer rising from roofs and pavement, and nearby smoke. If the air is unsteady, use shorter exposures and accept a softer image rather than forcing sharp focus on a turbulent frame.

Capturing a Partial Eclipse Sequence

Setup Steps

Mount your camera or telescope on a stable tripod or mount, and confirm that the mount can track the Sun. Attach the filter before you point the instrument toward the Sun, and keep the filter on until the eclipse is over. Aim using the finder or a shadow, never by looking through the optics. Use a solar viewer to check the Sun's position before you remove any protective cap from your camera.

Set a timer or an interval shooting function that records frames every few minutes. A regular interval makes it easier to assemble the progress into a sequence later. Record the time of each frame, and keep a note of contact times so you can match your images to the published timing.

Focus and Exposure

Focus on the Sun's edge using live view with the filter in place. Magnify the view if your camera allows it, and adjust until the limb is sharp. Because the Sun is bright, start with a fast shutter speed and a low ISO, then adjust by checking the histogram. Many photographers find that a fraction of a second at base ISO is a reasonable starting point with a certified filter, but test your own setup before the event. Avoid overexposing the disk, because a blown-out edge hides the Moon's outline.

Check focus and exposure every so often during the event. Temperature changes, wind and mount drift can shift the image, and a single check at the start is not enough for a long sequence.

Eye Safety

Whenever any part of the Sun's disk is uncovered, your eyes and any instrument must be protected by certified solar filters. This applies to every stage of a partial eclipse, including the first and last minutes. Use an ISO 12312-2 solar viewer for direct observation, and a full-aperture filter on any camera lens or telescope you point at the Sun. Do not remove the filter to check framing, because the Sun remains bright enough to cause harm even when it appears partly covered. Keep children and pets supervised, and never look at the Sun through a camera's viewfinder or an optical instrument without a certified filter in place.