Photo Ephemeris Web includes a number of tools to help you plan photography of solar eclipses. This page discusses the functionality available and how it is intended to be used. You should already be familiar with the basics of Photo Ephemeris Web before continuing with this tutorial.
If you are an experienced eclipse observer, you may wish to consult the Technical Note.
If you need guidance on camera settings (exposure etc.), we recommend Fred Espenak's advice.
What is a Solar Eclipse?
A solar eclipse occurs when the Moon passes between the Earth and Sun and casts its shadow on the surface of the Earth. Here's by far the best way to understand eclipses conceptually, courtesy of astrophysicist Katie Mack:
- <-- lunar eclipse
- <-- solar eclipse
- <-- apocalypse
There are three basic types of solar eclipses:
- Partial: the Sun is partly obscured by the Moon (magnitude is less than 1.00, obscuration, i.e. % area covered, is less than 100%)
- Annular: the Moon is positioned completely within the Sun, but is not close enough to Earth to cover it - this is the so-called 'Ring of Fire' eclipse (magnitude < 1.00, obscuration < 100%)
- Total: the Sun is completely covered by the Moon (magnitude >= 1.00, obscuration = 100%)
(You'll also see references to 'hybrid', 'annular-total', and 'broken-ring' eclipses - more on those below.)
Who can see a Solar Eclipse?
Lunar eclipses appear essentially the same for everyone on Earth, other than that the timing and position of the Moon in the sky varies based on your location and over time. But, if the Moon is risen, we all see basically the same phases of the lunar eclipse.
Solar eclipses are much more picky!
Because the Moon is small relative to the Earth, its shadow can at most reach a small portion of the Earth's surface during an eclipse. And, as the Earth is rotating, the point that the shadow reaches changes rapidly over time, during the course of the eclipse.
For this reason, what you see during a solar eclipse depends on where you are - and timing is everything.
What eclipse types should I care about?
All of them, of course! But, in reality, while a partial eclipse (a bite out of the sun, observed with proper eye protection) is interesting, it's not really where the 'action' is.
If you can get to observe a total eclipse, do it - it truly is an astonishing experience. (I write this having seen only one so far, in Aug 2017.)
Annular eclipses are also very well worth seeing, but don't bring quite the visual 'awe' of a total eclipse.
When will an eclipse occur?
In Photo Ephemeris Web, solar eclipses are included in the events list, for example:
You can find the dates of solar eclipses the events table. Broadly speaking, somewhere on Earth there are around two solar eclipses per year, more or less six months apart. The date and time shown are for the so-called 'General Circumstances' of the eclipse - the time corresponds to the moment when the greatest eclipse magnitude is reached, but says nothing about where that will be.
Where can I see the eclipse?
Now you know when an eclipse is happening, the next question becomes 'where can I see it'? When you select the date of the eclipse, a path is displayed on the map (zoom out if you don't see it):
The map shows the northern and southern limits of the path plus the central line.
The eclipse shown (Oct 14 2023) is an annular eclipse, so the path is shown where you can observe annularity (the 'ring of fire'). For a total eclipse, it represents the path of totality.
The central line is where the duration of the eclipse is greatest - i.e. the observer is 'deepest' in the shadow of the moon. The northern and southern limits show the transition area between seeing a total or annular eclipse vs a partial eclipse.
In the screenshot above, an observer at the red map pin location in Colorado will not see an annular eclipse, but only a partial eclipse.
IMPORTANT: eclipse paths are not currently shown for partial eclipses and may be missing or incomplete in polar regions. See Technical Note: Solar Eclipse Functionality.
When will it start and end?
To know when a solar eclipse will start and end, you need to know the local circumstances for your location. These will indicate key characteristics of the eclipse, in particular, the contact times. The contact times for a solar eclipse are defined as follows:
- C1, First contact: the moment when the Moon starts to cover the Sun, i.e. the start of the partial phase
- C2, Second contact: the moment in a total eclipse when the Moon completely the obscures the Sun - this is the start of totality. In the case of an annular eclipse, this is when the Moon moves completely within the bounds of the Sun's disc.
- Max eclipse: not strictly a 'contact' time, but this is the moment of greatest magnitude for the eclipse at the selected location
- C3, Third contact: the end of totality as the Moon no longer completely obscures the Sun (total) or moves outside the bounds of the Sun's disc (annular)
- C4, Fourth contact: the end of the partial eclipse, when the Moon no longer covers any portion of the Sun's disk
A partial eclipse only has C1, Max eclipse and C4. Total and annular eclipses have all five contact times. The closer you are located to the central line, the longer the time between C2 and C3, i.e. longer totality (or 'annularity').
Contact times are shown in the timeline for PRO subscribers. Here's an example for the Apr 8 2024 total eclipse, for an observer at Mazatlan, Mexico:
The azimuths shown are those of the Sun, although between C2 and C3, the azimuth of the Moon is naturally close to the same value. The value of 1.021 shown in the 'Max eclipse' timeline event is the magnitude.
You can adjust the selected time by clicking any event in the timeline or by adjusting the time slider (see also the Eclipse simulator notes below).
What will I see?
A note on eye protection
IMPORTANT: Eye protection is essential for observing eclipses at ALL times except during totality (between C2 and C3). Never observe the unobscured Sun without a certified solar filter, particularly through a telescope or camera lens.
The Eclipse Simulator
A simulation of the eclipse is available for PRO subscribers. It appears automatically at the lower right of the map when the selected date/time/location corresponds with a solar eclipse. To display the simulator, place the red pin within the eclipse path and select a date/time between C1 and C4.
The simulator shows the predicted appearance of the eclipse, together with some key data (magnitude, time until next contact, obscuration %). You can select any of the contact times from the controls at the top of the simulator, and in the case of C2 and C3, the times 5 seconds before and after the actual contacts - more on that below).
You can increase or decrease the zoom level of the image of the Sun and Moon by using a scroll gesture on your screen, mouse or trackpad.
In addition, you can use the play/pause button at the lower left to play back the simulation in real time (×1) or at an accelerated speed (×5 - good for totality, ×100 - good for the longer partial phase).
The current time and the value of DeltaT is shown at the bottom right (primarily for comparison with other eclipse data sources).
During the partial eclipse, the appearance of the sun/moon is shown - the position of the 'bite' will match what you can expect to see from the given location. Note that the obscuration (coverage) percentage is less than the magnitude - obscuration reflects the area of the Sun that is covered. The level of light in the sky is proportional to obscuration.
Diamond Ring before C2
In the case of a total eclipse, just before totality begins (C2) the diamond ring effect can be observed:
Note that magnitude is almost 1.000 and obscuration is almost 100%. The precise appearance of the diamond ring may vary based on the effects of the lunar limb - the peaks and valleys on the Moon's surface can cause the diamond ring to shift in position slightly, and Baily's beads to appear.
See the technical note for additional information.
C2 Second Contact
At C2 in a total eclipse, magnitude is 1.0 and obscuration is 100%. The simulator shows the time until C3 - this is the duration of totality, 4 minutes and 18 seconds in this case:
Two effects are shown in the simulator:
- the Sun's Corona, the outer atmosphere of the Sun, consisting of plasma that extends millions of miles above the surface. This is one of the most visually striking elements of a total solar eclipse. Its appearance can be predicted in advance, but only by a few days, and that lies outside our scope here. The image of the corona you see above, and that of the Diamond Ring effect above, are taken from the 2017 eclipse photographed in Alliance, Nebraska. They should be considered as representative, rather than authoritative!
- the Sun's chromosphere is visible as a very thin pale pink line at around 10 o'clock in the screenshot above. The chromosphere is another striking visual effect seen during totality and is easily captured by cameras (no filters required). Don't mistake it for chromatic aberration in your lens - it's the Sun's inner atmosphere!
At maximum eclipse, the magnitude reaches its greatest value. This occurs roughly half-way between C2 and C3. For 'deeper' total eclipses, i.e. those which occur with the Moon closer to Earth, and therefore apparently larger, the Sun's chromosphere is likely to disappear around this time:
C3 Third Contact
At third contact, magnitude is once again reduced to 1.0 (for a total eclipse - it never reaches 1.0 in an annular eclipse). The chromosphere has appeared once again at around 2 o'clock, along with a solar prominence - prominences vary in appearance from eclipse to eclipse, just like the corona, so again, this aspect of the simulation is figurative, not predictive:
Diamond Ring after C3
Before we return to the partial phase, the diamond ring once again appears at the calculated position angle derived from the local circumstances. Magnitude is less than 1, obscuration is less than 100% and eye protection is once again required:
The eclipse is now once again in its partial phase.
Adventures at the Edge
If you are a first time total eclipse observer, or have only seen a couple previously, you likely will want to maximize your time in totality and therefore should locate a point close to the central line and not too close to the extreme ends of the path.
However, if you're a veteran eclipse chaser, or are limited in where you can travel to, you may be observing from a location on the edge of the path. Here is where interesting things happen!
Observing near the northern or southern path limits
- The eclipse paths shown are accurate to only 1-2km due to the effects of the lunar limb and observer elevation above sea level (see Technical Note). If you position yourself very close the path limit, there's a chance you might miss totality!
- But - you'll likely observe plenty of: chromosphere and prominences (the Sun's limb is only just obscured by the Moon); Baily's beads (the topography of the Moon reveals glimpses of the Sun's photosphere during the course of the eclipse)
- We've read that Baily's beads can be more easily observed at the northern edge, presumably due to the greater variability of the Moon's topography
Observing near the ends of the path
- The ends of the eclipse path are defined by the limit of where the Sun is above the horizon - if the Sun is not visible, there's no eclipse to see
- If you're near the ends of the path, the Sun is by definition low on the horizon during the eclipse
- Atmospheric refraction will affect the appearance of the Sun and Moon and the shape of the Moon's shadow outline on the ground. The Sun and Moon may appear flattened or oblate. Timing is unaffected as the geometry of the eclipse alignment occurs outside the Earth's atmosphere
- Generally speaking, when the Sun is low on the horizon, the potential for interference from clouds and haze is greater
Recommendation: if observing at an edge location, be sure to read the Technical Note to understand limitations and consult other reliable sources to verify your plans.
Other eclipse types
Hybrid or Annular-Total
Certain eclipses are known as 'hybrid': they are observed as annular eclipses towards the ends of the path, and total at locations in the middle of the path ('ends' means the east/west limits and 'middle' refers to longitude rather than latitude, broadly speaking). Check the magnitude at max eclipse to determine the local circumstances. Examples from Apr 20 2023:
- At this location in the southern Indian Ocean, the eclipse was annular
- But near Exmouth, Western Australia, it was total
As the boundaries between the Sun's atmospheric layers are not discrete, there is a transitional zone in which an eclipse may appear not quite total or annular, but also distinctly different to a partial eclipse - this is the zone of the 'broken ring' eclipse. There is some debate on terminology and classification of such eclipses. It's primarily a philosophical divide between those who prefer definitions based on the mathematics of the circumstances vs. the on-the-ground observational experience. In any case, be aware that in eclipse circumstances where magnitude closely approaches or only just reaches 1.000, interesting edge effects are sure to be seen.
Some eclipses are characterized like this along much or all of the path, because the Moon's umbra only just reaches the surface of the Earth. A famous example is the hybrid eclipse of Apr 17 1912, occurring just two days after the sinking of the Titanic.
Near Paris, the path width is only 2km, and the eclipse scrapes its way to magnitude 1.000 for a grand total of 2.6 seconds! (Link)
So what sort of shot plan should you consider? As always, it depends. Options include (but are not limited to) long telephoto, medium telephoto, wide angle. Here are some brief thoughts and guidelines:
- If you have a 300mm (35mm equivalent) lens or longer, you can make the sorts of shots shown in the simulator above. There are many eclipse phenomena you can aim to capture, including:
- The 'diamond ring'
- Baily's beads
- The chromosphere
- Solar prominences
- The corona
- Generally speaking, eclipse phenomena are unique to each eclipse - the only exception possibly being the diamond ring, which can can appear similar from event to event.
- However, long telephoto shots are unlikely to become rarities - there may well be many photographers, depending on the location - and they won't really convey a sense of place (although, assuming your shot alignment is fixed relative to the zenith or ground, the orientation of the corona can give a clue as to where the shot was taken along the path)
- Medium telephoto shots (say 70-200mm focal length equivalent) may are suitable for locations where the sun is closer to the horizon (< ~20° in altitude) and can be juxtaposed against some other element (e.g. horizon, topography, even clouds? 😱). This shot plan might be the exception rather than the rule.
- Wide angle shots are the most likely to provide a unique record of an eclipse. Given the comparative rarity of an eclipse passing over the same the geographic area, if you manage to capture a wide angle view of, say, a total eclipse over a distinctive landscape, then chances are you'll have something rather special. I somewhat regret not making plans to shoot the 2017 eclipse somewhere over the Rocky Mountains in Wyoming for this very reason - there's not another opportunity to do that in my lifetime.
- That said, a wide angle shot necessarily cannot capture the distinctive aspects of the Sun's state at the time of the eclipse in the way a long telephoto lens can. If you only shoot wide angle, you may not even get to observe some of these phenomena.
- If the Sun is high is the sky at the time of the eclipse, wide angle compositions may be harder to find. You can check the required field of view using our Field of View calculator. The April 8 2024 eclipse on the central path north of San Antonio, TX will reach totality with the Sun at an altitude of +67°. To capture a foreground landscape, plus the eclipsed sun, you'd need to use a 14mm lens pitched up +30° - that's going to leave the Sun looking pretty tiny in your shot.
- Finally, if you're shooting a total eclipse, be careful not to lose precious seconds of totality to changing your camera setup. Stop shooting and remove solar filters with plenty of time to spare. Set up bracketed sequences so as not miss exposure sensitive details (e.g. chromosphere vs. the corona)
- Multiple photographers in your group? Divide and conquer. Alison and I managed to capture a variety of different phenomena between us back in 2017 - the only thing we missed were Baily's beads, likely because our central path location resulted in them being of short duration or not visible.
- Got multiple cameras? Great! Use them.
PS. If you need guidance on camera settings (exposure etc.), we recommend Fred Espenak's advice.
Suggestions and Feedback
Got any suggestions or feedback on this page? Please write to us - we'd love to hear from you.
- Besselian Elements: Eclipse Predictions by Fred Espenak, NASA/Goddard Space Flight Center Emeritus
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