Annular Solar Eclipse of January 26th, 2009
(Partial in northeast and southern India)
Chander B. Devgun
(President SPACE)

26th January 2009 has a special place in heart of every Indian as we celebrate our Republic Day. 2009 being the International Year of Astronomy, the Mother Nature has some goodies for us up her sleeves. An Annular Eclipse of the sun is happening on the Republic Day.

An Annular eclipse occurs when the Moon is farther from the Earth than normal, its apparent size is not quite sufficient to cover the Sun completely. Even though the Sun, Moon alignment is perfect, the Moon will appear slightly smaller in diameter than the Sun. A thin ring of sunlight will remain visible around the dark silhouette of the Moon. The name annular eclipse comes from the Latin word annulus, meaning ring.

The annular eclipse will be visible in the Indian Ocean, Indonesia and Borneo Island. Partial eclipse will be visible in a region covering South of Africa, Antarctica, South East Asia and Australia. In India the partial phases of the eclipse will be visible from southern part of India, all places in eastern coast of India, most of north-east India, Andaman & Nicobar Islands and Lakshadweep. The timings for different places in India have been given in the table at the end of this article.

ECa (Eclipse Chasers Athenaeum), the eclipse sphere of the SPACE has sent a team of astronomers to observe and webcast this eclipse from Indonesia. The eclipse will be webcast live on this site from Anyer Beach, Java, Indonesia (Latitude: 6° 03' 58" S, Longitude: 105° 53' 37" E) as per eclipse schedule below.

Timings for places in India have been given in separate table at the end of this article.

How to view the partial eclipse?

Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Everyday sunglasses are not safe, since they do not block the harmful and invisible infrared radiation which causes retinal damage. Only properly designed and certified solar filters should ever be used for direct viewing of the Sun's disk. Self-made filters using common objects like a floppy disk removed from its case, a Compact Disc, a black colour slide film, etc. must be avoided.
The safest way to view the Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. However, care must be taken to ensure that no one looks through the projector (telescope, pinhole, etc.) directly. Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe.

Projection method

Pinhole camera

Solar eclipse viewer

Geometry of an eclipse

Diagram of Solar Eclipse (not to scale)
The diagram shows the alignment of the Sun, Moon and Earth during a solar eclipse. The dark gray region below the moon is the umbra, where the Sun is completely obscured by the Moon. The small area where the umbra touches the Earth's surface is where a total eclipse can be seen. The larger light gray area is the penumbra, in which only a partial eclipse can be seen.

The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). Because of this, at the time of a New Moon, the Moon will usually pass above or below the Sun. A solar eclipse can occur only when the New Moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic.

As noted above, the Moon's orbit is also elliptical. The Moon's distance from the Earth can vary by about 6% from its average value. Therefore, the Moon's apparent size varies with its distance from the Earth, and it is this effect that leads to the difference between total and annular eclipses. The distance of the Earth from the Sun also varies during the year, but this is a smaller effect. On average, the Moon appears to be slightly smaller than the Sun, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to the Earth than average (near its perigee) that a total eclipse occurs.

The Moon orbits the Earth in approximately 27.3 days, relative to a fixed frame of reference. This is known as the sidereal month. However, during one sidereal month, the Earth has revolved part way around the Sun, making the average time between one New Moon and the next longer than the sidereal month: it is approximately 29.6 days. This is known as the synodic month, and corresponds to what is commonly called the lunar month.

The Moon crosses from south to north of the ecliptic at its ascending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion, due to the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.5 years. This means that the time between each passage of the Moon through the ascending node is slightly shorter than the sidereal month. This period is called the draconic month.

Finally, the Moon's perigee is moving forwards in its orbit, and makes a complete circuit in about 9 years. The time between one perigee and the next is known as the anomalistic month.

The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Therefore, the New Moon occurs close to the nodes at two periods of the year approximately six months apart, and there will always be at least one solar eclipse during these periods. Sometimes the New Moon occurs close enough to a node during two consecutive months. This means that in any given year, there will always be at least two solar eclipses, and there can be as many as five. However, some are visible only as partial eclipses, because the umbra passes above Earth's north or south pole, and others are central only in remote regions of the Arctic or Antarctic.

Facts about solar eclipses:

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring Earth's view of the Sun. This configuration can only occur during a New Moon, when the Sun and Moon are in conjunction as seen from the Earth.

An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the outline of the Moon.

Total solar eclipses are very rare events for any given place on Earth because totality is only seen where the Moon's umbra touches the Earth's surface.

The Earth's distance from the Sun is about 400 times the Moon's distance from the Earth. The Sun's diameter is about 400 times the diameter of the Moon. Because these ratios are approximately the same, the sizes of the Sun and the Moon as seen from Earth appear to be approximately the same: about 0.5 degree of arc in angular measure.

Because the Moon's orbit around the Earth is an ellipse, as is the Earth's orbit around the Sun, the apparent sizes of the Sun and Moon vary. The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse when the Moon is near its closest distance from the Earth (i.e., near its perigee) can be a total eclipse because the Moon will appear to be large enough to cover completely the Sun's bright disk, or photosphere; a total eclipse has a magnitude greater than 1. Conversely, an eclipse when the Moon is near its farthest distance from the Earth (i.e., near its apogee) can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Slightly more solar eclipses are annular than total because, on average, the Moon lies too far from Earth to cover the Sun completely.

Apogee & Perigee - The Moon moves on an orbit which is not circular but elliptical, with the Earth at one focus. At one end of this ellipse it makes its closest approach to the Earth (356 410 km or 221 473 miles), known as perigee. At the other end it reaches its greatest separation (406 697 km or 252 722 miles), called apogee. The period between successive perigees or apogees is called the anomalistic month, equal to 27.56 days.

 Annular Eclipse of 26th January 2009
Timings of Partial phases at places in India
(All times in I.S.T)

Place                  Begins             Greatest             Magnitude     Ends
Agartala             15h 01.5m       15h 31.8m         0.073             16h 00.7m
Aizawl                14h 58.1m       15h 32.3m         0.095             16h 04.6m
Bangalore          14h 33.1m       15h 16.6m         0.108             15h 56.7m
Bhubaneswar     14h 54.7m       15h 28.2m         0.079             15h 59.8m
Cannanore         14h 31.8m       15h 13.1m         0.092             15h 51.3m
Chennai             14h 28.9m       15h 19.1m         0.154             16h 04.8m
Cochin               14h 19.3m       15h 11.8m         0.150             15h 59.3m
Cuttack              14h 56.0m       15h 28.3m         0.074             15h 58.9m
Dibrugarh          15h 14.6m       15h 33.3m         0.030             15h 51.7m
Guwahati           15h 16.5m       15h 32.4m         0.020             15h 48.1m
Hubli                  15h 02.6m       15h 16.4m         0.011             15h 30.1m
Hyderabad         15h 02.2m       15h 21.3m         0.022             15h 39.9m
Imphal               15h 00.9m       15h 32.9m         0.085             16h 03.2m
Itanagar             15h 16.8m       15h 33.0m         0.022             15h 49.0m
Kanyakumari     14h 08.8m       15h 10.7m         0.215             16h 05.8m
Kavaratti            14h 31.5m       15h 08.2m         0.067             15h 42.4m
Kavalur              14h 28.7m       15h 17.4m         0.139             16h 01.8m
Kohima              15h 05.2m       15h 33.0m         0.065             15h 59.8m
Kolkata              15h 01.6m       15h 30.3m         0.062             15h 57.8m
Koraput              14h 54.7m       15h 25.5m         0.063             15h 54.8m
Kozhikode          14h 27.2m       15h 12.8m         0.113             15h 54.7m
Kurnool              14h 50.0m       15h 19.7m         0.052             15h 47.9m
Madurai             14h 16.9m       15h 13.8m         0.186             16h 04.9m
Mangalore          14h 40.5m       15h 13.5m         0.059             15h 44.7m
Midnapore         15h 03.9m       15h 29.8m         0.049             15h 54.7m
Murshidabad     15h 14.4m       15h 30.8m         0.020             15h 46.9m
Mysore               14h 31.4m       15h 14.9m         0.106             15h 55.0m
Nellore               14h 36.1m       15h 20.2m         0.118             16h 00.8m
Nowgang            15h 13.8m       15h 32.7m         0.029             15h 51.3m
Pondicherry       14h 24.1m       15h 17.6m         0.172             16h 05.9m
Port Blair           14h 17.6m       15h 25.8m         0.394             16h 25.9m
Puri                    14h 52.3m       15h 27.9m         0.090             16h 01.5m
Rajamundry       14h 46.3m       15h 23.6m         0.090             15h 58.6m
Sambalpur         15h 10.6m       15h 27.6m         0.020             15h 44.4m
Shillong             15h 11.0m       15h 32.4m         0.037             15h 53.2m
Sibsagar             15h 11.8m       15h 33.2m         0.039             15h 54.1m
Silchar               15h 03.6m       15h 32.5m         0.068             16h 00.2m
Sringeri              14h 42.7m       15h 14.7m         0.056             15h 44.9m
Tamenlong         15h 02.7m       15h 32.8m         0.075             16h 01.5m
Tanjore               14h 19.6m       15h 15.7m         0.186             16h 06.1m
Tirunelveli          14h 11.6m       15h 11.8m         0.204             16h 05.4m
Trichur               14h 22.2m       15h 12.4m         0.138             15h 58.1m
Trivandrum        14h 11.3m       15h 10.8m         0.196             16h 03.9m
Vijaywada           14h 46.3m       15h 22.4m         0.082             15h 56.3m