Annular Solar Eclipse 2010 at Cox’s Bazar : An AChokro Report

A solar eclipse is a rare cosmic phenomenon, especially a total or an annular eclipse. In a total eclipse, the moon completely covers the sun plunging the earth in n eerie darkness, whereas during an annular eclipse, the solar “ring of fire” peeks from behind the lunar disk. Bangladesh is fortunate to have paths of two eclipses pass over its territory within a span of half a year. These two events were very special considering the cosmic phenomenon is rare as the next total solar eclipse that will be observable in Bangladesh will occur in 2114 and the next annular eclipse will fall in the year 2064. Even though we will have the opportunity to observe numerous partial eclipses during the intervening period, the experience of observing a total eclipse is truly a remarkable one and cannot be replicated with partial eclipses.

On January 15, 2010, the moon’s antiumbra shadow passed over the southern tip of Bangladesh causing an annular eclipse of the sun. During an annular eclipse, the moon usually sits near the apogee, which is the farthest point of the moon from the earth making the angular size of the moon smaller than usual. At the same time, the earth is situated at the perihelion, the nearest point of the earth with respect to the sun making the angular size of the sun quite large. During this period, the lunar disk cannot fully compensate for the solar disk area and instead of a full obstruction of the solar disk, a “ring of fire” peeks out from behind the dark lunar disk.

The eclipse of January 15, 2010, started in mid-Africa, passed over Indian Ocean before crossing into southern Bangladesh and Myanmar. Later in the day, the eclipse could be seen from China. To observe and record the eclipse, Anushandhitshu Chokro Science Organization set up almost 20 observation points throughout the country, including a central camp at the Cox’s Bazar sea beach. Thousands of people gathered on the beach to observe this cosmic phenomenon.

Eclipse Photography

The annular eclipse in Cox’s Bazar started on 2:30 local time and lasted about 4 minutes and 45 seconds. The eclipse was photographed by a slew of cameras, including a Nikon D700 equipped with a 600 mm lens and a Nikon P90. A special Coronado Solar Telescope was used to track the eclipse and a Casio digital camera was placed at the prime focus of the telescope. In addition, a Sony video camera was mounted on an 8-inch Meade reflecting telescope to record the entire 3.5-hour event. A sole observer from Anushandhitshu Chokro recorded the event in St. Martin’s island where the eclipse lasted about 8 minutes and 30 seconds (see Figure 2).

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Fig 1: A composite of eclipse pictures taken through the Coronada Solar Telescope by Tarif Rashid Shanto.

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Fig. 2: Annular eclipse photo taken from Cox’s Bazar (photo: Noor Hossain)

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Fig. 3: Annular eclipse photo taken from St. Martin’s Island (photo: Naimul Islam Opu). The exposed solar ring is less asymmetrical compared to the photo taken at Cox’s Bazar.

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Fig. 4: A pair of sunspots were observed on the solar western limb. The spots were shown by the arrow signs. (Photo: Dipen Bhattacharya).

Pin-Hole Camera Projection

For the general viewing of the public, almost 50 pin-hole projection camera were constructed and setup at the Cox’s Bazar beach. These cameras project the image of the sun that passes through a tiny hole on a screen. These cameras allowed the general public to observe the eclipse in a safe manner.

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Fig. 5:An astronomy enthusiast with a pin-hole projection camera (photo: Ataul Hakim).

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Fig 6 A pin-hole projection of the annular eclipse in progression (photo: Nazmul Haque)

Solar Filters

Anushandhitshu Chokro also made 27,000 solar filters for safe viewing of the eclipse. The filters were made from Grade-14 Arc-Glass material which were suitable for safe viewing of the sun. The filters were made available at all observation camps.

Video Projection

A continuous video projection of the eclipse was shown through a LCD projector on a screen enacted within a covered enclosure. The video camera was mounted on an 8-inch Meade Reflecting telescope.

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Fig 7: Video Projection of the Eclipse

Eclipse Micro-Climate

A station fitted with temperature, light and humidity gauges was setup to measure the micro-climate created by the eclipse. Below we provide the preliminary graphs of the data. For the initial portion of the light values (lux) we used a mylar window, whereas later (post-annular) a 12-grade arc-glass filter was used. This explains the higher lux values after 15:35 hours.

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Two different temperature meters – one in shade (diamond/blue points) and the other under the sun (square/red points) – were used. The meter in the shade was a digital meter (S), whereas the meter in the light was an analog meter (L). The meters were calibrated within 0.1 degree Celsius and were placed on a wooden bench at a height of 30 cm above the sand. During the eclipse, a large temperature swing between 37 and 23 degrees was observed for the L meter, whereas the S meter in the shadow exhibited a drop from a maximum of 30.4 to a minimum of 24.2 degrees Celsius. Temperature drop was sharp for the L meter during the height of the annular eclipse, whereas the S meter minimum was not achieved until 15 minutes after the full eclipse. This, we believe, is partially due to the solid-state nature of the digital meter and partially due to time needed to achieve equilibrium temperature.

Future Analysis

The consolidated eclipse campaign was carried out to facilitate a safe and exciting observation for general public. We hope such programs will induce a positive learning atmosphere for science. In addition to this, Anushandhitshu Chokro carried out scientific measurements of the eclipse including the timings of the eclipse contact points from different geographical locations, observations of solar prominences, recording of temperature, humidity and light conditions, etc. Currently, we are in the process of analyzing the data. We hope such events will prompt young people to become more involved with science.