What’s a total Solar Eclipse?
A Total Solar Eclipse is a rare, astronomical event where the disk of the Sun slowly disappears over the course of a few hours during the day, briefly displays parts of the Sun we normally can’t see because of its glare and then re-appears just as slowly.
Total Solar Eclipses as we know them are unique to Earth and occur naturally nowhere else in the Solar System.
The easiest way to think about a Solar Eclipse is when the Moon covers the disk of the Sun and casts a shadow over the Earth. Because of a strange, celestial fluke, the size of our Moon and the Sun as seen from the Earth are the same during total solar eclipses.
Why is Totality the most spectacular phase of a Solar Eclipse?
Totality is when the disk of the Sun is entirely covered by the Moon.
The bright glare of the Sun’s Photosphere – the “surface” we normally see during the day – is blocked out by the Moon – so we can see some of the fainter details of the Sun.
This means that outermost regions of the Sun’s atmosphere called the Solar Corona (from the Latin for “crown”) are visible during a Total Solar Eclipse. It’s often possible to see a thin reddish pink line around the Sun’s disk. This is a region known as the Chromosphere which is a lower part of the Solar atmosphere. This extends some 2000km from the Photosphere. Solar Prominences are arcs of magnetised plasma that can be seen as “flames” between the Chromosphere and the Corona. (There’s also other phenomenon sometimes seen such as the Diamond Ring effect and Baily’s Beads which are not part of the Sun, but artifacts from the eclipse process itself.) Totality lasts only a short period of time, often only a couple of minutes or less. You can see the Chromosphere and Solar Prominences in this photo below taken during the 2017 Solar Eclipse.
Image via Jun Ho Oh (KAIST, HuboLab)
Please note that these features on the Sun don’t suddenly appear during an eclipse – they are always there. It’s simply the Moon blocking out most of the light from the Sun that lets us see these fainter details. (A dedicated Solar Telescope like the Coronado PST will let you see Prominences and details on the Chromosphere during any sunny day. They won’t let you see the Sun’s Corona – without highly specialised gear you’ll still need an eclipse to view this.)
Can we predict exactly what I’ll see during a Total Solar Eclipse?
We can predict the time, date of an eclipse for any location. Assuming clear weather, you’ll see the sky darken and once totality happens, you can expect to see the Solar Corona. The exact appearance of other features like Solar Prominences and the Chromosphere are harder to predict. Folks who’ve been lucky enough to experience several Total Solar Eclipses will comment that no two eclipses are the same!
When and where is The Ningaloo Total Solar Eclipse?
It’s called The Ningaloo Total Solar Eclipse as totality passes directly over Ningaloo in the far northwest coast of Western Australia. It also passes over the mining town of Exmouth. It will happen on the 20th of April 2023, starting at 10.03 am local time and finishes at 1.00 pm local time. Totality will last just over a minute and commences at 11.28 am local time.
Can I still see the Eclipse on the 20th April 2023 if I’m not in northern Western Australia?
Yes. A Partial Solar Eclipse will be visible across much of Australia
Areas outside the path of totality will experience a Partial Eclipse. This is when not all the of disk of the Sun is covered by the Moon. Much of Australia will experience a partial eclipse on the 20th of April. You can find a good eclipse map that you can use for the details of the Eclipse for your location here.
What a partial eclipse will look like depends on how far you are from the path of totality. Perth will see approx. 72% of the Sun covered. Over 20% of the Sun will be covered by the Moon in Adelaide, while Sydney will see just under 10% of the Sun covered.
Visit timeanddate.com to see what the 2023 eclipse will look like from your location.
Simulation of the 2023 Eclipse as seen in Perth via timeanddate.com
You won’t get to see the spectacle of the Sun’s Corona being visible during a partial eclipse, but it’s fascinating to see the slow progress of the Moon covering part of the Sun.
Why is this eclipse called a hybrid eclipse?
After Total and Partial, there’s another type of Solar eclipse called an Annular Eclipse. This is when the Moon is slightly further away from us appears too small and doesn’t cover the Sun’s disk entirely, leaving a “ring” of light visible.
An Annular Solar Eclipse in 2012 – Image credit: Dale Cruikshank
The Ningaloo Solar Eclipse is an even rarer event called a Hybrid Eclipse.
All Total Solar Eclipses are by their nature also Partial Solar Eclipses. Away from the thin path of Totality, the Eclipse will be a seen Partial Eclipse as mentioned above. A Hybrid Eclipse means at some point along the path of totality, due to the curvature of the Earth changing how the Moon is away from us, what was a Total Solar Eclipse becomes an Annular Eclipse.
How do I observe a Solar Eclipse?
YOU WILL NEED EYE PROTECT TO OBSERVE SUN AT ANY TIME!
There are several ways to safely observe the Sun, regardless of when an eclipse is happening. The easiest way it simply with a pair of eclipse glasses. These are low cost and hold special ultra-dark plastic film in front of your eyes to protect them from the Sun’s light, much like welding glasses or welding helmet. They’re only $4.50 from the BINTEL website.
Specialised binoculars for viewing the Sun are also available.
You can attach filters to the front of telescope and camera lenses to block excess light.
Can I photograph the eclipse?
Yes. BINTEL can advise on the best filters to protect your telescope and cameras. Given it’s now less than 100 days until the Ningaloo eclipse and with other eclipses in happening soon, it would be best to organise solar filters and accessories ASAP.
If you’re lucky enough to be in the path of totality, is it worth considering simply observing the eclipse with your eyes or a telescope or binoculars? There will be lots of photos taken and this is an exceedingly rare event!
Any equipment used for viewing or photographing a Solar Eclipse can be used for Solar observing or imaging when an eclipse is not happening. The Sun is complex and its surface is always changing.
Why don’t we have a Solar Eclipse every month as the Moon orbits the Earth?
The Moon must be at a particular point in its orbit around the Earth for its shadow to hit the Earth’s surface. The Moon also orbits the Earth at a slight incline meaning the shadow it casts every month will usually “miss” the Earth. We tend to think of the Moon as being close by as especially during a Full Moon it seems like we can almost touch it. As you can see from the pic below, there’s quite a distance between us, about 400,000 kms.
You might get an idea of just how tricky it is for the Moon to cast its shadow on the Earth.
Image via NASA
How often does each place on the Earth have an eclipse?
On average, each part of the Earth’s surface sees a total Solar Eclipse about once every 400 years. As much of our planet’s surface is covered with water, the chance of seeing one on land is greatly reduced! There’s a Total Solar Eclipse somewhere on Earth about every 18 months. Eclipses also occur in complex patterns and cycles.
Can I go blind looking at Solar Eclipse?
You need eye protection to directly view any type of Solar Eclipse and special filters for telescopes, binoculars and cameras.
There’s no special light or radiation that is transmitted from the Sun during an eclipse. Eye damage can be caused by normal sunlight. The reason Solar Eclipses are dangerous is that during a normal sunny day, we can’t look at the Sun for more than a few moments without it becoming extremely uncomfortable and this causes us to reflexively look away. During a Solar Eclipse the Sun’s brightness is dimmed and it can trick our brain into thinking it’s safe to look at for longer periods of time. This combined with our curiosity about Solar eclipses makes them a hazard when viewed without proper equipment.
The damage the Sun does to our eyes is called solar retinopathy. As people tend not to stare at the Sun during the day and eclipses are rare events, scientists don’t have a full picture of both the short and long-term damage it can do to our eyes. Solar retinopathy can be temporary, lasting days or a few months. There are cases where pain and loss of a significant percentage of eyesight is permanent.
While it might be unwise to view a Solar eclipse with just your eyes and this might result in a temporary injury, directly viewing the Sun through even a small telescope or binoculars will put your eyesight in enormously more danger. A telescope collects and concentrates light. For example, viewing the Sun through just a basic 70mm telescope without proper filters would focus an image of the Sun some 100 times brighter than what you’d normally see, directly onto the delicate retina at that rear of your eyeball. The resulting injury would likely be the immediate and permanent total loss of sight in that eyeball. Please don’t be tempted to even have a quick look at the Solar Eclipse unless your telescope of binoculars are fitted with proper Solar filters.
Why are the “flames” of Solar Prominences reddish-pink in colour?
Most of the Sun is hydrogen, the simplest and most abundant element in the Universe. This is slowly being turned into helium and other elements by nuclear fusion, and vast amount of energy is released by this process. Hydrogen gas in the outer parts of the Sun’s Chromosphere absorb this energy and then emit photons at certain wavelengths, one of which appears reddish-pink to the human eye. It’s the same process the causes the same colours, although across a wider and less dense region, in both the Orion and Triffid nebulae.
Bear in mind Solar Prominences are vast in size, often dwarfing the Earth in comparison.
As always, this is a complex topic and we’ve only touched on the basics. You’re welcome to add any comments or suggestions.