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Partial Solar Eclipse

posted Nov 30, 2011, 1:25 AM by Unknown user
Just before sunset on Friday the 25th of November 2011, New Zealand was one of very few places on Earth where a partial solar eclipse could be seen!

A solar eclipse is when the Moon moves in between the Earth and the Sun. Very curiously, as seen from Earth, the disc of the Moon is almost exactly the same size as the disc of the Sun! This amazing fact means that the Moon can cover the Sun! This is called a “solar eclipse”.
If the Moon only covers a part of the Sun’s disc, it is called a “partial solar eclipse”, and this is what happened on November the 25th.



This picture is copied from Cartes Du Ciel free sky chart software, it shows this partial eclipse at 8.20pm.


This eclipse was visible in New Zealand from New Plymouth southwards, and also from Tasmania, the tip of South Africa, and Antarctica.

In New Zealand the eclipse started just before sunset, and the Sun would set before the eclipse was over. For more information visit http://www.rasnz.org.nz/Eclipses/2011Eclipses.htm#Sun4

In my case, living in Wellington, a high hill seemed a good place to get a reasonably clear view of the horizon to the West, where the Sun would set. So I headed to the Mt Vic Lookout.

To observe this event, I used a 70mm refracting telescope, with a glass solar filter mounted on the front end of the telescope tube. This way the sunlight first hits the filter, where it gets filtered to safe levels, before reaching the optics of the telescope, and then ultimately the eye of the observer! Our eyes are very precious and we need to protect them well, this is at the heart of all solar observing.

The Sun transmits at great intensity, and at many wavelengths, not only visible light. As an example, the Sun also transmits at ultraviolet and infrared wavelengths, which are harmful to the eyes.

It is important to protect our eyes from sunlight. Especially when the sunlight is magnified in a telescope or binoculars, you can permanently damage your eyes. This glass solar filter is specifically manufactured for solar observing. It blocks 99.999% of the sunlight. But not only that, it also blocks the harmful ultraviolet and infrared wavelengths.

Unless you have a correct filter, don't look directly at the Sun, through a telescope, or in any other way. You eyesight is simply too valuable!

Sketch of this partial solar eclipse

This sketch was made after the event. You can see the Moon eclipsing the Sun from the left. Within about 8 minutes from the start of the eclipse it had progressed to the stage you can see in the sketch. The Sun is "bubbly" around the edges, because of the heat radiating off the land at the end of the day (like a mirage). A few sunspots were visible. The lower part of the Sun is already setting behind a hill with a tree on it.

It was awe inspiring to see the solar system in action like this!



Solar observing is great to do! Do it safely before anything else. If you are interested, come and talk with us at the Levin Stargazers.

Keep bright and safe,
Mike Stapel


P.S. finally, some light reading:

http://sunearthday.nasa.gov/2012/transit/viewing.php

http://eclipse.gsfc.nasa.gov/SEhelp/safety.html


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Unknown user,
Nov 30, 2011, 1:36 AM
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