Eclipses 101; An Extraordinary Astronomical Alignment

Solar Eclipse

“O dark, dark, dark amid the blaze of noon,

irrecoverably dark, total eclipse without all hope of day!”

John Milton

Photographed seconds before totality on Nov. 14, 2012 -Palm Cove Australia

An eclipse of the Sun can only occur on a New Moon, when the Moon passes between Earth and Sun aligned in a straight line, and positions close to a lunar node. When the Moon ‘occults‘ the Sun, day temporarily turns to night and the stars become visible. This phenomenon is always location specific on Earth.

solar eclipse diagram-pderrick

The solar eclipse is the result of the moon being at, or near perigee (closest) to Earth as it is the only time when the disk of the Moon looks big enough to cover the entire disk of the Sun when viewed from Earth. A Moon at perigee is called a Supermoon.

There are 4 types of solar eclipses- Total, Partial, Annular, Hybrid (- an Annular turning Total or vice versa which is an extremely rare occurance).  In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.

Partial, Total, Annular & Hybrid Solar Eclipses

Certain phenomena can only be seen during a total solar eclipse: (

    1. Shadow bands: About 1 minute before totality, moving wavy lines of alternating light and dark can be seen on the ground and along walls. These shadow bands are the result of Earth’s turbulent atmosphere refracting the last rays of sunlight.
    2. Diamond ring: Seen about 10 to 15 seconds before and after totality, the solar corona (the outer atmosphere of the sun) becomes visible; seen together with a single jewel of light from the sun, this creates a diamond ring effect.
    3. The Sun’s corona: As the diamond ring fades, the Sun’s corona becomes more prominent and is visible as a faint ring of rays surrounding the silhouetted Moon. The corona is the outermost layer of the Sun’s atmosphere, and it is around 200–300 times hotter than the Sun’s surface. The corona’s temperature can reach over 1 million °C (1.8 million °F).
    4. Baily’s beads: About 5 seconds before totality, Baily’s beads appear. They are little bead-like blobs of light at the edge of the Moon. They are created because gaps in the mountains and valleys on the Moon’s surface allow sunlight to pass through in some places but not others.
    5. The Sun’s chromosphere: A lower layer of the Sun’s atmosphere, the chromosphere, gives out a reddish glow which can only be seen for a few seconds after totality sets in.
    6. The phenomena then repeats in reverse order : The Bailey’s beads grow and merge into a crescent as the Moon continues to move away. Then as the diamond ring grows brighter, the corona fades. Lastly the Shadow bands -the moving wavy lines reappear on the ground shortly before the crescent Sun becomes visible again and nature recovers

Nodal Reference: A Solar Eclipse must occur if the New Moon is nearer than 15°23’ to the Node, or if the Moon’s celestial latitude is less than 1°23’. There is no eclipse if a Node is farther than 18°21’ from luminary, and Moon’s celestial latitude is greater than 1°34’

To see a total solar eclipse one must be located along a narrow path on Earth’s surface, the path taken by the Moon’s shadow (umbra) as it sweeps across Earth. At such times, those outside the shadow path, but still near it can see a partial solar eclipse. Those located in the path of the umbra, experience the day sky turn black and the stars reemerge; a fall in temperature and the winds drop and change direction. The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse.

With the path of a total solar eclipse blocking all of the Sun’s light, the length of this total blockage – at any given location on the eclipse path usually lasts three to four minutes. The maximum duration of a total solar eclipse is 7 min 40 sec (total – at equator) and 12 min 24 sec for annular eclipse. This area of total darkness moves along the eclipse path at a speed of approximately 1000-5000 miles per hour, depending on the speed of the Moon.

Image of the August 11th 1999 eclipse shadow
Lunar Eclipse

“Eclipsed by the orbs shadow, the lady will give us a red light this night. A show for lovers who look deeply into the night and watch the moon turn the color of love.”

C.J. Thompson

Blood Moon – Full lunar Eclipse

An eclipse of the Moon can only occur on a Full Moon, when the Earth passes between the Sun and Moon and they are aligned in a straight line and close to a lunar node. The Earth thereby blocks the reflected light from the Sun to the moon and Earth’s shadow causes the Moon to turn shades of copper and red, hence the term Bloodmoon. The type and length of a lunar eclipse depends upon the Moon’s location relative to its orbital nodes.

lunar eclipse-edited2

There are 4 types of lunar eclipses: Total, Partial, Penumbral, Appulse ( when the Moon moves through only the Earth’s penumbra and is only slightly dimmed). Earth actually casts two shadows that fall on the Moon during a lunar eclipse: The umbra is a full, dark shadow. The penumbra is a partial outer shadow. The Moon passes through these shadows in stages. The initial and final stages — when the Moon is in the penumbral shadow, are not so noticeable, so the best part of an eclipse is during the middle of the event, when the moon is in the colorful umbral shadow.

While the Moon remains completely within Earth’s umbral shadow, indirect sunlight still manages to reach and illuminate it. This is because sunlight passes deep through the Earth’s atmosphere which bends or refracts some of this light filtering out most of the blue colored light, so that just a small fraction of it can reach and illuminate the Moon. The remaining light is a deep red or orange in color and is much dimmer than pure white sunlight.  If the Earth had no atmosphere, then the Moon would be completely black during a total eclipse.

Nodal Reference: A total Lunar Eclipse must occur if the Moon is nearer to the Node than 04°09’, and may occur if the Moon is between 04°09’ and 05°34’ from the Node, especially if the Moon’s celestial latitude is not greater than 00°52’. A partial Lunar Eclipse must occur if the Moon is between 05°34’ and 09°30’ from the Node and may occur if the Moon is between 09°30’ and 12°04’ from the Node, especially If the Moon’s celestial latitude is not more than 01°03’

A lunar eclipse is visible anywhere on Earth where the Moon can be seen, thus approximately half the earth can observe a lunar eclipse. A lunar eclipse lasts for a few hours, whereas a total solar eclipse lasts for only a few minutes at any given place, due to the smaller size of the Moon’s shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the Full Moon.

Total Lunar Eclipse – The Blood Moon

The position on the lunar nodes are calculated by determining the intersection point of two paths of rotation -the orbit of the Earth around the Sun, and the orbit of the Moon revolving around the Earth. The planes of these two orbits intersect each other at 5 degrees, 8 minutes and 40 seconds. The line of intersection is the polarized axis formed by the Moon’s Nodes. The Nodes do not move at an entirely predictable speed and vary from day to day. Since the Moon travels along an orbit which is inclined by 5 degrees to the Ecliptic plane, there are only two opportunities each month for the alignment of an eclipse- when it passes through the plane of the Ecliptic, called the ascending and descending nodes.

The Nodal Axis – Ascending and Descending
Eclipse cycles and series

“Men should take their knowledge from the Sun, the Moon and the Stars”

 R.W. Emerson

Eclipses tend to run in sequences of pairs or threes: solar-lunar-solar approximately spaced 6 months apart. A lunar eclipse is always preceeded by, or followed by a solar eclipse (with two weeks between them). If the solar eclipse is total then the accompanying lunar eclipse in that sequence will be partial and vice versa. As many as 5 solar eclipses can occur in one year. At most there are 3 lunar eclipses in a given year – and there may be NONE. Therefore lunar eclipses are a rarer occurrence than solar eclipses. Yet even with at least 4 annual solar eclipses, viewing a full eclipse in your area is still a fairly rare event. According to retired NASA astrophysicist Fred Espenak a total solar eclipse is visible from any spot on Earth about once every 375 years on average. In the world, a total solar Eclipse occurs on average once every 16 months or so.

Lunar Eclipse and Solar Eclipse

Most years such as 2017 have only four eclipses (solar + lunar), although you can have years with five eclipses (2013, 2018 and 2019), six eclipses (2011 and 2020) or even as many as seven eclipses (1982 and 2038).

The periodicity and recurrence of eclipses is governed by the Saros cycle. One Saros-cycle takes 1000-1200 years to be completed and is made up of about 42 sun-eclipses, a period of approximately 6,585.3 days (18 years 11 days 8 hours). It was known to the Chaldeans as a period when lunar eclipses seem to repeat themselves, but the cycle is applicable to solar eclipses as well.

Artistic version of Saros Cycle 145 (solar). Actual diagram by J.Schulz: ‘Rhythmen der Sterne’

The diagram above shows the actual cycle of the ‘zones of totality’ wandering southwards starting at the North pole and completing at its southern opposite. This actual cycle had its first eclipse in 1639 and will be completed in 2648 with its last eclipse over the South pole – therein commencing again on North pole. Solar eclipses are birthed then at one pole and progress towards the opposite pole, marking the termination of that Saros cycle.

The “Great American Eclipse” on August 21st 2017 is a member of Saros 145 – no 22, in the series. The longest duration eclipse in the cycle will be member 50 at 7 minutes and 12 seconds in length after which the duration of eclipses will decrease until the end of the cycle. In its central phase it will produce mainly total eclipses (41 of 43 central eclipses).


Saros series are numbered according to the type of eclipse (solar or lunar) and whether they occur at the Moon’s ascending or descending node. Odd numbers are used for solar eclipses occurring near the ascending node, whereas even numbers are given to descending node solar eclipses. For lunar eclipses, this numbering scheme is somewhat random. The ordering of these series is determined by the time at which each series peaks, which corresponds to when an eclipse is closest to one of the lunar nodes. For solar eclipses, the 40 series numbered between 117 and 156 are active, whereas for lunar eclipses, there are now 41 active saros series.

Geometric  multiples of 9

As for the relationship between solar and lunar saros- after a given lunar or solar eclipse, after 9 years and 5.5 days (a half saros) an eclipse will occur that is lunar instead of solar, or vice versa, with similar properties. For example, if the moon’s penumbra partially covers the southern limb of the earth during a solar eclipse, 9 years and 5.5 days later a lunar eclipse will occur in which the moon is partially covered by the southern limb of the earth’s penumbra. Likewise, 9 years and 5.5 days after a total solar eclipse occurs, a total lunar eclipse will also occur. This 9-year period is referred to as a sar. It includes 111.5 synodic months, or 111 synodic months plus one fortnight. The fortnight accounts for the alternation between solar and lunar eclipse.

Eclipse effects

“Astronomy compels the soul to look upwards

and leads us from this world to another.”


Earth’s magnetic field

When the Moon is full or new, the gravitational pull of the moon and sun are combined. The moon exerts a pull on the Earth on other days too, but it is not as powerful as on the days of Full Moon and New Moon. At the time of the New Moons and Full Moons, the “extra” pull causes higher tides on Earth. An eclipse New Moon, or Full Moon is an intensification of this “extra” pull, since an eclipse is an exact line up of the Sun, Moon and Earth. For Solar Eclipses the Earth’s geo-magnetic field is altered. Thus it stands to reason that every living creature on Earth- any entity with an individual bio-magnetic field will also be affected.

Tidal Force of the Sun and the Moon on Earth

The fact that humankind even witnesses solar and lunar eclipses here on Earth is phenomenal because it requires EXTRA-ORDINARY planetary alignment. Science tells us that our planet and its inhabitants live in a long time phase where the positioning in space of Earth, relative to Moon and Sun is EXACTLY aligned to produce the eclipse effect here on this planet…this will not always be the case in the far, far distant future.

Sun, Earth and Moon in alignment

The Sun currently is about 400 times larger than the Moon from the perspective of Earth, while the Moon is about 400 times closer to the Earth than the Sun. This astounding similarity in the relationship between the size of the Sun and that of the Moon, together with the proximity of the Moon to the Earth compared with the Sun from Earth creates the possibility of a total solar eclipse. It has been calculated that in approximately 650 million years from now, the very last total solar eclipse will occur, as beyond that point, the Moon will no longer be close enough to Earth at any point in its orbit to have its shadow fall on our surface. How can one not marvel then at this unique cosmic design, gifted to humanity in this period of our planets growth and development; how since the dawning of civilization, humans with their consciousness have evolved and been privy to the transformational effects of eclipses for thousands of years…

Spectating a Total Solar Eclipse

“Three things cannot be long hidden: the Sun, the Moon and the Truth”


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