The Total Solar Eclipse of April 8, 2024

The Total Solar Eclipse of April 8, 2024

Update April 5: we have unfortunately run out of eclipse glasses, and so have Tourism London and the London Public library. As of yesterday, Forked River Brewery still had a few dozen pairs available. And this Sunday,  Virgin Radio is giving away free eclipse glasses while supplies last.

You can still try to order online. Many vendors have sold out as well; these may still have stock (but it is not clear whether you can still get them on time): 

https://www.ppe-supply.com/products/sun-catcher-solar-eclipse-glasses

https://usa.all-startelescope.com/pages/solar-eclipse?shpxid=b6fddd83-e166-4aa7-a692-6ad1ff02b363

https://ontariotelescope.com/solar-glasses/

https://khanscope.com/collections/solar-filters

 

In the afternoon of Monday, April 8, 2024, a total solar eclipse will be visible from a narrow path that stretches from Mexico to Newfoundland and Labrador and includes parts of Ontario, but just misses London, where only a partial solar eclipse will be visible. This web page provides basic information about this awe-inspiring celestial event, important safety information and resources to help you prepare for this unique experience. You can also watch this presentation about what to expect by Cronyn Director Prof. Jan Cami.

In London, the partial eclipse starts at 2:01pm. The maximum of the eclipse occurs at 3:17pm, and the eclipse ends at 4:29pm.
Note that the Cronyn Observatory will not be open for the public on eclipse day — all astronomers will be traveling to be in the path of totality. 

First this: London will not experience a total eclipse since it is not in the path of totality. The path of totality is just south of London (see below). St. Thomas for instance will experience a total eclipse. London will experience a 99.6% partial eclipse and this is a very different experience than a total eclipse! The difference between a 99.6% partial eclipse and a total eclipse is quite literally the difference between day and night! It is definitely worth considering traveling a bit to the south to get the full total eclipse experience.

What is a total solar eclipse?

A solar eclipse is the phenomenon where the Moon moves in front of the Sun. If the Moon completely blocks the Sun, this is a total solar eclipse; if parts of the Sun remain uncovered, this is a partial solar eclipse. Total solar eclipses happen on average about once every 18 months or so. However, they are only visible from a fairly narrow path,which is why for any given spot on Earth they only occur once every 375 years on average — quite rare indeed! Partial solar eclipses are much more frequent, and in fact the last partial solar eclipse that was visible from London was just half a year ago — on October 24, 2023 — but unfortunately it was overcast that day. You can read more about the frequency of eclipses on this site: timeanddate.com  and more about eclipses in general on this cool NASA site: nasa.gov/eclipses

Where can we experience the total eclipse in the neighbourhood?

The eclipse of April 8, 2024 will be a total eclipse over a narrow path that lies just south of London. To find out more about the specifics for any given location, have a look at this interactive map. It shows the narrow path of totality. You can zoom in, and then click on any point on the map to get more information about the eclipse at that specific location. For instance, at the location of the Cronyn Observatory, the magnitude at maximum will be 0.99374, meaning that 99.374% of the Sun will be covered by the Moon — a partial eclipse indeed. The path of totality is indicated by the two red lines, and the centre line is indicated in blue. You can see that St. Thomas is just inside the path of totality; but the closer you get to the central line, the longer the total phase will last. Clicking at the centre of St. Thomas for instance, it says there is a total solar eclipse where the totality lasts about 1m14s; precise numbers depend on where you click on the map — there’s already 30 seconds difference in the length of totality between the north and the south of St. Thomas. Port Stanley beach will see 2 minutes of totality. Buffalo is smack on the centre line and will see 3m45s of totality.

Interactive map showing the path of totality

How different is a partial solar eclipse from a total eclipse?

A 99.6% partial eclipse sounds pretty close to a total eclipse, but the experience is something entirely different, and certainly not something like a 99.6% total eclipse! The last ray of sunlight to be blocked by the Moon during totality is what quite literally makes the difference between day and night. There is a good write-up about the difference between the two here: space.com . As everybody who has ever seen a total eclipse can tell you: it is worth traveling for, especially if you don’t have to travel far!

Watching the eclipse safely

You should never, ever look directly at the Sun without proper eye protection — except during the brief phase of totality (see below). The lens in your eye focuses sunlight onto your retina and burns it. This can lead to temporary or permanent damage to the eye and in the worst case result in legal blindness. “If people look without the proper protection [at the sun], they run the risk of injuring their eyes. And if they get an injury, depending on how often and how long they look at the sun without the protection, they do have a substantial risk of developing a permanent loss of vision,” said Dr. B. Ralph Chou, president of the Royal Astronomical Society of Canada and a former optometry professor. There are no immediate symptoms or pain associated with the damage — the retina doesn’t have any pain receptors — so its hard to know at the time if you’ve actually been afflicted with eclipse blindness. You can read more about eye safety and eclipses here: eclipse2024.org 

One of the best ways to ensure eye safety is to get your hands on a pair of good eclipse glasses. Beware of online shopping though, as not all products offered online are good quality. There is a list of trustworthy online dealers here: eclipse eye safety .

If you don’t find eclipse glasses, there are other ways to safely follow the eclipse during the partial phase, for instance by making a pinhole camera. There are many examples online how to build one; here is one particularly easy case: How to make a pinhole camera 

If, and only if, you are in the path of totality, you should remove your eclipse glasses during the total phase. During that brief phase, the sunlight is 100% blocked by the Moon, so removing the glasses is safe, and will in fact be necessary for you to see anything at all. The end of totality is easy to spot: this is the famous and breath-taking diamond ring phase. This is the sign that totality is over, and you should put your eclipse glasses back on immediately. You can only safely remove the eclipse glasses during the total phase of the eclipse. Under no circumstances should you look at the Sun without adequate protection during the partial phase — not even if it is a 99.9% partial phase!

Weather prospects

Eclipses can only really be experienced well if skies are clear during the eclipse. Unfortunately, the weather in early April tends to be quite cloudy, at least statistically speaking. You can find that out on this site: eclipsophile.com . This, of course, is only a statistical conclusion. Check the weather forecast a few days in advance to figure out where you will have the best chances of clear skies.

More resources