The Annular-Total (or Hybrid) Solar Eclipse of 20 April 2023.
A Hybrid Eclipse occurs when the Moon is only just close enough to the Earth to give a Total Eclipse along some of the central path. At the edges, the Earth curves away from the Moon and the Moon is then too far to cover the Sun completely. At these points the eclipse is Annular (ring shaped) instead of Total.
The narrow blue region is the Path of Totality of the eclipse (also known as the Umbra).
The Moon's umbra (shadow) travels from West to East (left to right on the map). The first part of the path (in red on the left) is annular. The majority of the track gives a total eclipse. The last part (right, red) is also annular.
At the point of Greatest Eclipse (red star in the centre of the path), Totality is at local midday. The duration of Totality at greatest eclipse is 1 minute 16 seconds. This occured in the sea just to the south of East Timor. On either side of that point, the duration of Totality is less. To the West (left) of the point of greatest eclipse, the eclipse is total before local noon; East (right) of this point, Totality is seen after local noon. The umbra is generally widest around the time of greatest eclipse as the Earth is bulging out towards the Moon in that region. This brings the Earth's surface closer to the Moon.
The area on either side of the path of Totality (in pale blue) is called the Penumbra and provides a partial eclipse, the magnitude decreasing with distance from the path of Totality. Beyond the partial region no eclipse is visible.
The Sub-solar Point is the location where the Sun is overhead at the time of greatest eclipse; in April this point is North of the equator. The parts in red on either end of the umbra are the regions where the eclipse occurs during sunrise (left) or sunset (right).
The path of Totality began in the southern Indian Ocean with an annular eclipse at sunrise. It remained in the ocean until it passed over the extreme West of Australia. It moved North East and crossed over the eastern part of East Timor. After another ocean crossing dotted with a few islands it passed over Irian Jaya in Indonesia.
The umbra left the Earth from the Pacific Ocean with an annular eclipse at sunset.
The umbra took 3 hours 20 minutes to traverse its entire path.
27% of all solar eclipses are total. Hybrid eclipses make up less than 5% of all solar eclipses.
The Path of Totality (the Moon's Umbra) is the shaded area just touching the Ningaloo Peninsula in Western Australia from bottom left to top right.
The Moon's shadow took 4 minutes to move across mainland Australia and another minute to pass a few of the country's islands.
The yellow marker indicates the position of Exmouth, the only town on the peninsula.
The only town in the Path of Totality is Exmouth. The town was less than 10km North of the centre line and its centre experienced Totality lasting 0m 56s.
The only airport on the peninsula, Learmouth was also less than 10km from the centre line, but to the South and had totality of 0m 56s.
Exmouth was our eclipse base as it had the only facilities.
The Centre Line of the Path of Totality is shown in blue in the region of Exmouth.
The Path Width was 41.5km in this region and the duration of Totality at the coast on the centre line was 1m 02s.
Exmouth was less than 10km from the centre line in a perpendicular direction but 15km by road.
Our location was on a beach to the South of the town.
A free shuttle bus connected the town centre, our accommodation and the beach every 15 minutes.
| Date | 20 April 2023 |
| Location | Town Beach, Exmouth, Western Australia |
| Latitude | 21° 56' 47" S |
| Longitude | 114° 08' 22" E |
| Altitude | 5 m |
| Distance from Centre Line | 7.0 km |
| 1st Contact (UT + 8) | 10:04 |
| 2nd Contact | 11:29:48 |
| 3rd Contact | 11:30:47 |
| 4th Contact | 13:03 |
| Duration of Totality | 0m 59s |
| Path Width | 41.5 km |
| Direction of Shadow Approach | ~ 220° |
| Umbral Velocity | 0.769 km/s |
| Solar Altitude | 54° |
| Solar Azimuth | 022° |
| Position Angle: 2nd Contact | 026° |
| Position Angle: 3rd Contact | 245° |
| Gamma | -0.3951 |
| Diameter Ratio | 1.012 |
| Saros Details | 129 (52 / 80) 1424 years |
The Location, Latitude, Longitude and Altitude (in metres) are for the observation site at Town Beach South of the centre of Exmouth.
The Distance from Centre Line was estimated from Google Interactive maps provided by Xavier Jubier.
First Contact is the beginning of the eclipse when the first "bite" appears on the Sun's disk; it is the beginning of the partial phase. Second Contact is the beginning of totality. Third Contact is the end of totality. Fourth Contact is the end of the partial eclipse. The times are in local time which, for this eclipse, is UT (GMT) + 8.
The Duration of the eclipse at the observation site was 0 minutes 59 seconds. This was 3s shorter than the duration at the centre line further South along the coast.
The Path Width is the width of the path of totality. The umbra itself was slightly elliptical in shape. The umbra at the observation site had a path width of 41.5km.
The Direction of the Shadow indicates that the umbra approached the observation site from South of West.
The Umbral Velocity is the speed of the Moon's shadow (769 metres per second) at the observation site. This, and the size and shape of the umbra, determines the duration of the total eclipse.
The Sun's Altitude is measured from the horizon; the Azimuth is the direction of the Sun measured clockwise from North. The figures are for mid-eclipse. The figures mean that the Sun was high and almost due North.
The Position Angles indicate the exact position of the Sun's disk where the Moon covers and uncovers the Sun at the beginning and end of Totality. These figures determine the position of any diamond rings or Bailey's beads at the beginning and end of Totality.
Gamma determines how the Moon's shadow, if extended, would pass through the Earth.
A Gamma of zero implies that the shadow would pass through the exact centre of the Earth. A Gamma of greater than 1 misses the Earth and no total eclipse would occur. A positive Gamma passes North of the Earth's centre; a negative Gamma passes South of the Earth's centre. The value of Gamma for this eclipse is -0.3951. This means that the shadow passes nearly half of the way between the Earth's centre and the Southern part of the Earth. This, combined with the fact that in April, the North Pole is tilted towards the Sun, produces an eclipse mostly in the Southern Hemisphere.
The Diameter Ratio determines how much bigger the Moon's apparent radius is than the Sun's. In this case, the Moon's radius is 1.012 that of the Sun's. A total eclipse can only occur if this figure is greater than 1. The Moon would then appear larger than the Sun and could cover it completely. If this figure was less than one a total eclipse could not occur because the Moon would appear smaller than the Sun.
For this eclipse the value of the Diameter Ratio means that the Moon appears nearly 1.2% larger than the Sun. In other words, it only just covered the Sun.
The Saros is a collection of eclipses belonging to a series. Each member of the series is followed by a similar eclipse approximately 18 years, 10 / 11 days and 8 hours later.
The eight hours has an interesting effect. Each eclipse is about 120 degrees West of its predecessor because 8 hours is a third of 24 hours.
This eclipse is a member of Saros number 129. It is the 52nd eclipse out of a total of 80 in the series.
The series began on 3 October 1103 with a small partial eclipse (5.6%) in the Northern polar regions. This was followed by 19 more partial eclipses each of increasing magnitude.
On 6 May 1464 the series produced the first of 29 annular eclipses (with a duration of 4m 17s). These began in the Northern Hemisphere with each subsequent eclipse moving generally southwards until the final purely annular eclipse on 18 March 1969 which had a duration of 0m 26s. The longest of the annular eclipses was on 4 October 1698 and lasted 5m 10s.
The next three eclipses (29 March 1987, 8 April 2005 and this eclipse, 20 April 2023) were hybrid with increasing amounts of totality as the Moon was moving towards the Earth.
The next eclipse in this series (30 April 2041, duration 1m 51s) will be the first of 9 total eclipses in the Southern Hemisphere. The longest duration of totality will be for the eclipse of 25 June 2132 (3m 43s). The final total eclipse of the series will occur on 26 July 2185 and will last for 2m 27s.
The series will end with 19 partial eclipses in the Southern polar regions, each successive eclipse of smaller magnitude. The final eclipse will be a 2.2% partial on 21 February 2528.
The series will produce 80 eclipses: 39 partials, 29 annulars (ring shaped), 3 hybrids and 9 totals. The series lasts for 1424 years.
At any one time dozens of Saros series are in progress. Other eclipses will belong to different series.
