The 2024 Eclipse Simulator

Instructions for use

Important Notice - Please read this first!

The eclipse simulator is a free educational tool and is intended as a general guideline for displaying the possible appearance of the 2024 solar eclipse from any given location. does not endorse or approve any specific viewing site related to the 2024 eclipse. Selection of a suitable viewing site, including due diligence, weather, infrastructure, travel, logistics, time zones, and safety considerations, is solely the responsibility of the eclipse observer. Electronic tools such as this simulator are subject to potential errors in display, rendering, calculation, performance, accessibility, and accuracy. All information displayed in the simulator is provided "as is", with no warranty or guarantee as to suitability of any specific location for viewing the eclipse, that the simulator will be uninterrupted or error-free, or that the simulator is suitable for any specific purpose of the viewer. makes no warranties or representations regarding the accuracy, completeness, or reliability of any information displayed in the simulator.


Click here for more information on eye safety.

The simulator is an online tool that allows you to see the 2024 total eclipse as it will appear from basically any location in North or Central America, the Caribbean, Greenland, Iceland or Hawaii. The area we've defined for use is as shown on the map in our location selection page.

The simulator is the best tool we've seen for showing you what the eclipse will look like from any given location. It is as accurate as we can make it, and if you've never seen an eclipse before, you'll be amazed at what they look like! If it inspires you to get into the path and see totality, then we've done our job.

Even if you can't make it into the path, you'll still be able to preview what the eclipse will look like. However, certain caveats are in order (for example, how the prominences and the corona might appear), and you can read more detail about these below.

You can experience the eclipse before it happens! This will let you:

  • Pre-plan your eclipse day viewing activities
  • See the differences between what it's like to view the eclipse from inside the path, at the edge of the path or outside the path
  • Find the best spot for viewing Baily's Beads
  • Experience the eclipse well before eclipse day, so you can share the excitement with your friends!

You are watching a simulation on a screen, so no eye protection is required for using the simulator. In real life, during an actual eclipse, you DO need to be careful about eye safety – and you WILL need to have ISO-certified eye protection ready. Make sure you read and understand all the instructions for watching an eclipse in real life before the big day arrives!

In the simulator, we show you with a special red banner at the top when you would need to be using eye protection during the real-life eclipse. You can click on the links within that banner to order eclipse glasses, or to visit the eye safety section of our site and learn more.

Having said that, we have to remind you that no matter what times you see displayed on the simulator screen, and no matter what the simulator says about using or not using eclipse glasses, on eclipse day you MUST still follow the one and only rule of eye safety: If any part of the Sun's bright disk is showing (even a sliver or a bead), you MUST use ISO-certified eye protection to view the eclipse.

In the meantime, there's no need to worry about that while using the simulator! recommends using the simulator on either the Chrome or Opera browsers. It has been tested on Safari, Firefox, and Internet Explorer as well, and gives good results on those. Other browsers have not been tested.

You'll also find that it's not really best to use the simulator on a small-screened device. There's just too much going on! We've tried to fit everything in the best we can, but it just goes to show that there's nothing like seeing an eclipse live and in person.

Wouldn't it be nice to be able to predict the weather in advance? Different types of sky conditions (clouds, haze, etc) do indeed affect eclipse viewing. Attempting to simulate that is beyond the scope of this project – and besides, we really don't want to see ANY clouds on eclipse day!

The simulator is designed with a perfect weather day in mind, and wishes you nothing but CLEAR SKIES on eclipse day!

When the simulator first loads, you'll see some pop-up instruction boxes. These will cycle you through the "big four" controls which allow you to navigate forward and backward in time, zoom in and out, and run a simulation at whatever speed you like. These controls work just as you'd expect them to, but we've provided a little more detail in the sections below.

You can use the zoom control on the left to zoom way in and see a great amount of detail in the eclipse events, or zoom way out and see the entire landscape and sky in the direction of the Sun. Drag the thumb of the zoom control up to zoom in, and down to zoom out.

You can also use your mouse wheel to zoom: Scroll forward to zoom in, and backward to zoom out.

Use this control to zoom way out and see the big picture: the hazy sky getting ominously darker during the minutes before totality, the orange glow on the horizon during totality, or the stars coming out as the sky darkens.

You can also zoom way in and see closeup effects such as you might see through a properly-filtered telescope. You'll be able to see things like the chromosphere, prominences, the last sliver of the disk fading away, Baily's Beads, the Diamond Ring – all the things you'd see in real life!

There are two time sliders you can use. The big slider at the bottom is the main one, and it moves you quickly backward or forward through time. The smaller slider just above it is the "fine" time slider, which gives you very accurate control of the simulation time. When you use the small slider, the clock shows you tenths of a second.

Use the main slider to get close to the time you want, and then use the fine slider to get exactly to the time you want. Every time you move the main slider, the fine slider will re-center. From that centered position, the fine slider will give you about 30 seconds of movement earlier and later from that point.

If you run out of room using the fine slider, just move the main slider again; the fine slider will re-center.

You'll also notice that the main slider adjusts time differently as you get closer to the time of totality. During the partial phases, the slider moves you faster through time than it does during totality, or mid-eclipse. This allows you to have more control of your position in time whenever the most important eclipse events are happening quickly.

You most likely got to the simulator from another page on our site or from a QR code you scanned. In this case, the location will be pre-loaded for you. If you want to change locations, you can use the "Select Location" link in the top left corner to be taken back to our interactive map. You can select a new location there very easily.

When the simulator loads, you will see a generic scene in the foreground. But we've also incorporated a feature that lets you select some slightly more realistic foregrounds. This scene can be anything we want, and of course it will not be the same as where you are. Just select whatever scene you like from the "Scenes" dropdown.

The simulator will show you any scene you select, so be careful not to select a nice grassy field if your viewing location is actually somewhere at sea!

The foreground scene that you select makes no difference at all to what you'll see in the sky. If you only want to see the eclipse, you can even select "none" as your foreground.

When the simulator loads, we've done our best to guess the time zone you'll want to see in the simulation, based on the location you're using. If that time zone isn't the one you want, then we've given you a list of time zones that you can choose from. They are at the bottom right of the screen.

You can read our detailed explanation of time zones on the main site, or you can simply select whichever time zone you want to use. Note that "GMT" is the standard reference time used by astronomers, but unless you're in Iceland, it won't be YOUR time zone on eclipse day!

To find out what time zone a particular place is in, you can search online. You can ask people around you, or you can also ask your favorite digital personal assistant. But remember, …

REMINDER: On eclipse day, most of North America will be using Daylight Time. This is why you only see a few time zones listed that use "ST" in their names. You will want to select a time zone that uses "DT" in its name unless you know for a fact that your location does not observe daylight time – locations like Puerto Rico, the Caribbean, Hawaii, and parts of Arizona and Saskatchewan. For absolute accuracy, we recommend you find out well in advance what time zone you will be located in on eclipse day – April 8, 2024.

Here is a list of time zones supported by the simulator:

Time Zone Name UT offset* Where Observed
GMT Greenwich Mean Time
(Also known as
Universal Time or Zulu Time)
0 Iceland
(Astronomers, pilots, and the military also use it)
PMDT Pierre and Miquelon Daylight Time GMT - 2 St. Pierre and Miquelon
NDT Newfoundland Daylight Time GMT - 2.5 Newfoundland
(and a couple towns in Labrador)
WGST Western Greenland Summer Time GMT - 3 Greenland
ADT Atlantic Daylight Time GMT - 3 Many of the Maritime Provinces of Canada
AST Atlantic Standard Time GMT - 4 Puerto Rico and the Caribbean
EDT Eastern Daylight Time GMT - 4 Eastern USA and Canada
EST Eastern Standard Time GMT - 5 Quintana Roo, and a handful of communities in Canada
CDT Central Daylight Time GMT - 5 Central USA, Canada and Mexico
CST Central Standard Time GMT - 6 Saskatchewan
(the same as MDT, as used in Alberta)
MDT Mountain Daylight Time GMT - 6 Rocky Mountain region of Canada, USA and Mexico
MST Mountain Standard Time GMT - 7 Sonora and most of Arizona
PDT Pacific Daylight Time GMT - 7 Western Canada, USA and Mexico
AKDT Alaska Daylight Time GMT - 8 Alaska
(except the Aleutian Islands)
HST Hawaii Standard Time GMT - 10 Hawaii

*This "offset" is the difference between GMT and the given time zone. For example, if it's 12:00 GMT, then to get EDT you would subtract 4 hours and end up with 8:00 EDT.

You can move the time sliders yourself to get an idea of what the eclipse will look like in real time, or you can start the clock and let the simulator run. To do that, click on the white arrow near the clock slider at bottom left. The eclipse simulation will proceed, and the clock will show you the simulated time.

You can slow down or speed up the simulation by using the clock slider control. When the simulation first loads, your clock speed is set at 1x (normal speed). This is a good compromise for seeing most events, but it is too slow for the entire partial phase series, and a bit too fast for Baily's Beads study. Change it however you like, even while the simulation is running.

Hit the pause icon to stop the simulation. You can always move around in time by using the sliders, and then re-start the clock. You can also use the time sliders to reposition yourself in time while the clock is running, but remember that the clock will keep running until you pause it!

There are a lot of menu and display items in the simulator, and if the simulator window is sized down too much, there won't be enough room for everything to fit. If you don't see a control that you'd like to use, look inside the hamburger menu – it'll probably be in there!

The shape of the corona is one thing that cannot be predicted far in advance. We have a feature built into the simulator that lets us create different "sample" corona shapes, and you can select one of the examples we've made by changing the selection inside the "Corona" dropdown.

The Sun undergoes a cycle of sunspot activity that varies from "Minimum" activity to "Maximum". The shape of the corona during totality can be somewhat predicted by where the Sun is in that cycle when the eclipse occurs. A "Solar Minimum" corona will generally be elongated, and a "Solar Maximum" corona will be more rounded. If the eclipse occurs in between the points of maximum and minimum, then the corona will be somewhat "Mixed", with both long and round elements. We've included several coronas of each type, so you can see them for yourself. (Just to note, a solar maximum is predicted for Summer 2025. This leads astronomers to believe that the corona for the 2024 total eclipse will be more rounded. But no one knows for sure until we see it!)

About a week or two before every eclipse, astronomers who study these things will come out with their best-guess predictions of what the corona might look like. When we get this info, we'll add it to the simulator, but please remember – it's still only a best guess. When you see the corona on eclipse day (if you're in the path of totality), you'll be seeing it for the first time – right along with everyone else!

This is the very thin outer layer of the Sun's disk that sits right at its edge, and is a very unmistakeable red color. It is only visible when the eclipse is "almost" total. We've simulated this as best we can, so you can zoom in and watch as the last sliver of Sun turns from yellow to red, and is then broken up by Baily's Beads as the Chromosphere disappears and totality begins.

If you're located at the edge of the path, you'll see an extended display of chromosphere and Beads. Many people position themselves there because they find this fascinating to watch!

Prominences are those red things you'll see sticking out from the edge of the Sun. In reality, they are massive outbursts of solar material, many thousands of miles in height, that shoot out from the Sun's surface.

Like other solar phenomena, the shape of the prominences can't be predicted in advance. Sometimes there won't be very many at all, and sometimes we get lucky and there are huge prominences on display during totality.

Whatever they turn out to be, to the casual observer they will not change shape at all during totality. Once you see them on eclipse day, they won't move around or grow.

The simulator selects a small random number of prominences, chosen from our large collection of samples, and places them at random locations on the Sun's disk. This is the best we can do, since we don't know in advance what they will look like, where they will be located, or how many there will be.

One thing you will certainly want to see in the simulator: Watch during totality as the Moon moves across the Sun, and either slowly covers or uncovers the various prominences. This is an amazing thing to see during the actual eclipse, as you watch the Moon move in its orbit around the Earth!

In real life, the Diamond Ring is what you see when the last bit of sunlight just barely remains visible through that last lunar valley, right before totality starts. The sky is darkening greatly at this point, and the "Diamond Ring" is an effect you experience during that brief period of excitement just before totality.

People who watch eclipses from the edge of the path report that the Diamond Ring doesn't have as much of an impact in those locations. This is because the beads really dominate the scene from the edge, and the sky stays reasonably dark during the whole process. We've incorporated this feature into the simulator.

This is a very subtle effect, but if you position yourself at a location where the shadow is coming toward you from the direction you're looking, then you'll be able to see the Moon's shadow approaching from the West or the Southwest.

This stunning effect is only visible during the very last few seconds before totality. (It's even better if you're located high above the surrounding horizon, on a cruise ship with the ocean as your flat horizon, or high above the ground in an airplane!) You'll be able to see the dark shadow appear to "rise up" out of the horizon and cover the entire sky as totality begins. When the edge of that black "curtain" touches the Sun in the sky, that's when totality starts. The effect is very humbling in real life, and is a worthy culmination to all the excitement leading up to totality.

In the simulator, we've made the effect very subtle – just like what you'll see in real life. (It is most prominent if you're on the centerline.) To give you the most accurate rendering of this phenomenon, we've based the appearance of the shadow in the simulator on the detailed calculations of its exact location and shape as seen from your position.

NEW FEATURE as of January 2023! (Dedicateed to the memory of the late Dr. Jay Pasachoff)

If you’re simulating the 2024 total eclipse, in a location where the maximum magnitude is more than 97%, you’ll be able to see the Moon’s shadow in the sky just like in the real eclipse! (Why 97%? Well, if the magnitude of the eclipse is less than that, you’ll simply never be able to see the shadow in the sky – it’s too far away from you!)

In a real eclipse, the Moon’s three-dimensional shadow forms a very long, narrow cone in space, whose tip scrapes across the surface of the Earth. If you’re in or near that shadow, then you’ll see it in the sky as it passes over you. If the Sun is low in the sky, you’ll also be able to see the shadow clearly as it approaches you. It’s a very amazing experience!

What you’ll see in the simulator is a very subtle shading of the sky, possibly with some color banding (depending on the color depth of your display), that appears to move through the sky just before, during, and just after totality. And if you’re in a place just outside the path, you’ll also see the movement of this darkening effect even though the eclipse won’t be total for you. If you’re at a location where the Sun is very low in the sky during mid-eclipse, the sky darkening will be very pronounced.

The effect is extremely subtle in most cases, and this matches what happens during a real eclipse. But because it’s so subtle, it can be very difficult to observe. To let you see the shadow better, we’ve provided a “Study Shadow” mode. If you check the box labeled “Study Shadow”, the main sky darkening will be turned off. (This could NEVER happen in a real eclipse!) In this mode, we still show you things like the stars, the orange horizon glow, and the appearance of the Sun during the eclipse. But all the other sky-darkening features are turned off so that all you see in the sky is the Moon’s shadow sweeping by. Check it out! Select a location in or near the path, set the simulation to a time near mid-eclipse, check the “Study Shadow” box, and move the main time slider back and forth. The effect is truly amazing.

Is this accurate? How do you do it?

The short answers are "Yes", and "A lot of math"! The rectangular projection of the real sky on the simulator view window creates some unavoidable distortion, but the overall location and darkening of the shadow in the sky is accurate. The position of the Moon’s shadow with respect to the observer is known at all times. The simulator generates the set of 3D vectors drawn from the observer to the point in the sky represented by each pixel on the viewing window, and then decides whether each of those thousands of vectors intersects the Moon’s shadow cone. For those that do, the distance from the observer to the near and far edges of the shadow is calculated. That determines how much to darken the sky for that pixel. This process is repeated for every pixel, and for each instant of the eclipse. The result is what you see: a simulation of the Moon’s shadow sweeping past you. It’s just one more amazing thing you can look forward to experiencing during the eclipse!

Once totality has begun, you'll see something that eclipse chasers always tell you to look for – the orange "sunset" glow that extends all around the horizon. This glow is present because locations that are far away on your horizon are not in totality; the Sun's light is as bright as day over there, and any sunlight that is getting over to you has had to travel horizontally through a lot of atmosphere to make it this far. Just as all that air absorbs so many wavelengths of light to make sunsets appear orange, this horizon glow will also be orange. It is another stunning effect of totality that is impossible to miss.

The glow will be very even if you are on the centerline. However, if you are close to the edge of the path, or if you're in a location where the shadow is very long in one direction, you may not see orange at all in some places on the horizon. The simulator calculates the distance to the edge of the shadow at every moment, in every direction, and includes that detail in determining how bright or dim the orange glow will be.

In the top right corner of the screen, you’ll see a “Shadow Map” whenever the eclipse is close to being total. This is an overview map that is centered on your location, and it shows the position of the dark shadow of the Moon at whatever time is being displayed in the simulator. If you move the sliders or run the clock, you’ll see the shadow move along with the time.

The simulator uses the shadow outline on the Earth’s surface to calculate the orange glow on the horizon. The glow is always strongest in the directions where there is just the right amount of shadow between you and the horizon. If you’re too close to the opposite edge of the shadow, there won’t be much glow. If there’s too much shadow between you and the horizon, then the glow is too far away for you to see it!

You can resize the Shadow Map window to show more of the map, and you can click the check box below the window to turn the Map on and off.

The Shadow Map window is only available when the shadow is close to your location. The eclipse has to either be total, or a partial eclipse of more than 97% coverage.

One of the features of the simulator that we are most proud of is its ability to show you the actual appearance of Baily's Beads, as they will appear from your simulated location. We'll describe them below, but to see them best, you'll need to zoom way in and check the "Study Baily's Beads" check box at top left. This will turn off the corona and other effects, and will give you the best view of the Beads at all times when they are visible.

(Checking this box for a partial eclipse, or during the partial phases of a total eclipse, will not affect what the simulator is showing you. It only has an effect during totality.)

As the Moon covers up more and more of the Sun, we see the bright part of the Sun (through your eclipse glasses, of course!) as a very thin sliver that shrinks – slowly at first, and then quickly in the moments just before totality. At a certain point, that thin sliver of Sunlight is so thin that it gets broken up by the mountains and valleys at the very edge of the Moon. This causes you to see alternating bright and dark areas instead of a continuous thin strip of sunlight. Baily's Beads are those last remaining bits of the bright disk of the Sun, and they do indeed look like beads! They move around and change shape in real time as you watch them, and what they look like is very much dependent on where you are located.

It used to be that we had only a basic idea of the Moon's rugged topography at the edge of its disk. When NASA launched the LRO, and we began to receive detailed lunar terrain information, it became possible to calculate where and when the Beads would become visible, and exactly what they would look like.

As you might imagine, it is very difficult to do this. A LOT of math is involved, but has done all the heavy lifting for you. In the simulator, you'll see how the beads will actually appear from your given location, as determined by all these calculations. And if you look very carefully, you'll see that we're also displaying the effect of the lunar mountains and valleys on the chromosphere! Look for that as variations in the thickness of the red chromosphere after the last beads have faded away, but before totality starts. The chromosphere is still visible for just a few seconds at that point! It is an extremely subtle effect, so don't be disappointed if you don't see it at first.

Another thing you might try is to position yourself on the edge of the path. (You can do this by using the "Select location" link at the top left of the screen.) At these locations, the beads don't just take place at the beginning and end of totality – they can actually occur for the entire duration of the deepest phase of the eclipse! Many people go to the edge of the path intentionally, sacrificing seconds or minutes of totality for the chance to the see the sparkling Beads dance around the edge of the Moon. But just as a warning - you have to be EXACTLY (within 200 yards or so) on the edge of the path to get this effect!

Remember that when you observe Baily's Beads, you are looking at actual pieces of the Sun's bright light streaming through valleys on the Moon. This means that you have to use eye protection to watch them in real life. You won't have that worry in the simulator, though – so study them to your heart's content!

To see Baily's Beads in the best way in the simulator, you'll need to check the "Study Baily's Beads" checkbox and zoom WAY in. This will let you see the Beads without any distractions. (You have to be in the path, or at the very edge of the path, for this to have any effect on what you see.)

Check this box to see the round outlines of the Moon and Sun. Of course, you wouldn’t see these in the real sky, but it can be helpful to see the full outline of the Moon as it moves over the Sun. It also makes the Sun easier to see when you are zoomed way out. (See how the Moon looks so much bigger than the Sun? This is because at this particular time, it's close enough to the Earth that a total eclipse is even possible!)

You will definitely be able to see the brightest stars and planets during totality, if you know where to look. We are lucky for the 2024 eclipse, because both Venus and Jupiter will be very prominent for most eclipse observers. The famous constellation Orion will be to the "left" of the Sun, as well.

In the simulator, you’ll see the stars during totality, as well as after sunset (if the eclipse is still going on at sunset - this only happens far out in the Atlantic Ocean). You can move your mouse over any star or planet to see its name and brightness. Astronomers call an object's brightness its "magnitude" - the is NOT the same as the "magnitude" of an eclipse! (Learn about what “magnitude” means.)

The 2024 eclipse only occurs at sunset in the middle of the ocean, well east of Newfoundland. Even though most people will not be able to view totality from there, we’ve included sunset features (like the apparent "squishing" of the Sun and Moon caused by the atmosphere, and all those pretty sunset colors) in the simulator for those locations so you can experience it for yourself! (This is not really applicable to the 2024 eclipse, but it will come into play spectacualrly for the 2023 annular eclipse!)

This feature is included in the simulator to show you just how bright the Sun actually is. It’s difficult to simulate how bright it looks – and that’s not part of the eclipse anyway! But we’ve put this option in place so you can see the big difference between how the Sun regularly appears, and how amazing that contrasts with what happens during totality. Normally, the glare of the Sun completely overshadows everything else, and that’s why you need eclipse glasses to protect your eyes – even when you are watching a 99.9% partial eclipse.

Experiment a bit:

  • Move to the beginning and the end of the eclipse using the large time slider. This will show you how the eclipse progresses over the course of the day.
  • Turn on the outlines of the Sun and Moon to watch how the Moon’s disk moves over the Sun – even during totality!
  • Place yourself somewhere on the edge of the path, and watch Baily’s Beads dance around the edge of the Moon’s disk.
  • Place yourself just outside the path, and see how the Moon just barely misses covering up the entire Sun. You can also see some of the eclipse effects that WILL be viewable from those locations. (This is most helpful for people who cannot make it into the path, but would still like to know what they’re going to get to see.)
  • Zoom out and watch the shadow rush up to you from the west in the moments before totality.
  • See what stars will be visible during totality.
  • Study the characteristics of the eclipse that are the same – or different – from viewing locations in Mexico, the USA and Canada.
  • Place yourself far from the path and see what a very small partial eclipse looks like.
  • Learn conclusively when you will need to use your eye protection. (The presence of the red banner at the top of the screen will give you a guide, but remember to follow all the rules in the Instructions for viewing the eclipse!)


  • See how much of the Sun has to be covered up before the sky becomes noticeably dark.

This is because different screens and different computer settings only display a certain number of colors. While that number of colors is very large, it may not be enough to cover all the possible variations of color that are present within a wide and ever-changing gradient. We’ve done our best to smooth out that gradient, but some browsers (like Firefox) or screens currently just don’t display it as well as we’d like.

We’ve found the best results to be on a plasma screen, and in the Chrome browser. We haven’t yet seen any examples of where this banding interferes with the basic concept of what’s being portrayed on the screen, though – it’s just a limitation of technology that you certainly won’t see in the real sky on eclipse day!

You might expect to be able to click and drag the display around in order to view what’s going on in another part of the sky. Because of the way all the eclipse effects are drawn, a lot of calculating is done when the simulator first loads. Moving around the sky would require a lot of real-time calculation updates that would make your experience with the simulator not as good as we’d like. To avoid slowing down the display, we needed to disable clicking and draging to move around.

As a trade-off, we have a formula in place that keeps the Sun in a comfortable viewing position on the screen. This is true regardless of your location, the time of day, or the zoom factor you’re using. We also show you compass directions so you can keep your bearings at all times. (It will also help if you keep the simulator window at the largest size your monitor will allow.)

The Diamond Ring is a bright phenomenon, but it is small compared with the size of the Sun’s disk. To see it, you must be zoomed in to at least a zoom factor of 5 or so.

And if you are at a location near the edge of the path, the Diamond will not be as obvious to you. At these locations, the Beads dominate, and the events are happening too slowly to give you the large and sudden changes in brightness that create the "Diamond" effect.

If you are zoomed way out, and the eclipse is in a very deep partial phase, then you could lose sight of the Sun altogether. That’s simply a limitation of the display, caused by that very small sliver of Sun being smaller than what can be displayed by the pixels of a screen using standard technology.

If you’re in this situation, just zoom in a little. The Sun will become visible again!

Yes, in the simulator it does (and so do the stars). For performance reasons, we have had to compromise a bit on the way the curved sky is portrayed on a flat screen. You may remember from school that the classic Mercator projection really distorts land masses in the far North – for example, making Greenland look larger than Africa. We are using a similar projection in the simulator (called a "Plate carrée projection"), and that causes objects that are higher up on the screen to shift more over time than they would in the real sky. In the real sky, for instance, you would NOT see the Sun shift by more than one of its diameters during the time of totality. But if the Sun is high in the sky during totality from the location you’re simulating, you’re going to see it move more than you would in the real sky.

We have maintained the round shape of the Sun and Moon, and their relative positions to each other as well as to the stars. We have also maintained the accuracy of the directional labels you see at the bottom of the screen. The result is a compromise that does not detract from what you’ll see when it comes to the eclipse events and phenomena. If you need 100% positional accuracy (including RA/Dec or alt/az coordinate grids) for all the celestial objects, we’d recommend using an astronomical tool like Celestia, RedShift, Stellarium, or others. (But they don’t show all the various eclipse phenomena as well as our simulator!)

The goal of the simulator is to show you what the various eclipse effects and features look like. For each eclipse phase, we’ve simulated the use of eye protection or not, depending on whether you need it at that time.

For example, everything you see during totality is what you’d see WITHOUT eclipse glasses on.

During the partial phases, the view of the Sun is filtered down to what you’d see WITH eclipse glasses on. (Though that’s not true of the scenery in the foreground. Looking through eclipse glasses, you wouldn’t see any foreground at all, but we needed to keep the horizon in place so you could maintain your bearings.)

When you’re zoomed in and looking at Baily’s Beads, you’re seeing what the eclipse would look through a certified solar filter installed on a video camera, binoculars, or telescope.

In every case, in real life you must follow this simple rule: IF ANY BRIGHT PART OF THE SUN IS VISIBLE, YOU MUST USE ISO-CERTIFIED ECLIPSE SAFETY GLASSES!

But with the simulator, we’re not endangering our eyes at all. That means we can show things as they would appear to someone who is using the most appropriate eye protection at all times, according to the viewing instructions we all have to follow. And we can pick and choose what we show at any time, to make it as helpful for you as possible!

Yes. Behind the scenes, we can update delta-T (and even the Besselian Elements) on the fly, as predictions are further refined during the run-up to eclipse day. You can be sure that we will stay on top of this critical and ever-changing value, to keep the simulator as accurate as possible.

We have included the 2023 annular eclipse in the simulator, because that will be an event of great interest for those in North and South America during the lead-up to 2024’s total eclipse. We are planning to add more eclipses to the simulator in the future, as well. Please look for those, coming soon!

Even with the limitations it has, we expect the simulator to make a very positive contribution to eclipse study among scientists and the general public. Thousands of hours of effort went into creating this tool, and what you see is the result of the power of math combined with the art of capturing the actual experience of witnessing a solar eclipse. We also believe very strongly that the eclipse (and the sky itself) belong to everyone, and it’s all about giving YOU the best information possible, as you prepare to observe the 2024 eclipse!

Ultimately, two things were in play to create the majority of the features you see on display in the simulator: First, the raw mathematics of calculating the Moon’s location, movement and libration (the "wobbling" that it does during the course of its orbit) are performed for every viewing location in or near the path of totality. This in itself was a major undertaking, as eclipse calculations – even with Bessel’s great method – are very difficult. Lunar libration calcuations are even more intricate, and are really impossible to simplify if you want to achieve a usable level of accuracy. And as any astronomer will tell you, predictions involving the Moon are very intricate; the Moon is strongly acted on by the gravity of nearly every other body in the solar system, and for precise results literally hundreds of effects must be taken into account!

Second, the various events that you see during the eclipse were simulated based on the calculations of magnitude, time, location, libration, lunar/solar elevation, and all other factors – according to the observations, memories, and recollections of the most experienced eclipse observers, using algorithms we designed specifically for the simulator. The specialized calculations for Baily’s Beads, for instance, are on the cutting edge of what is currently possible mathematically. Only in the last few years has the eclipse community become fortunate enough to receive and incorporate NASA’s LRO lunar topography data into eclipse predictions, and this has become the gold standard of expectation for veteran eclipse observers everywhere.

We created this simulator to bring you the best possible tool for learning about eclipses, and for helping you plan your eclipse day viewing activites. On April 8, 2024, you’ll be treated to the REAL show, and we can only hope that you’ll find it many times more inspiring and amazing than we’ve been able to capture in the eclipse simulator!

CLEAR SKIES to all, from!