Dominic Ford, Editor
From the Eclipses feed
The Moon will pass in front of the Sun, creating a solar eclipse. From some parts of the world, the alignment will be so exact that the Moon will completely cover the Sun and the eclipse will be total.
The path of the total eclipse will pass through United States.
A partial eclipse will be seen from numerous other countries, including:
|Country||Extent of eclipse|
|Canada||Sun 89% covered|
|Cape Verde||Sun 88% covered|
|Bermuda||Sun 86% covered|
|Bahamas||Sun 79% covered|
|Antigua and Barbuda||Sun 77% covered|
|Sint Maarten||Sun 77% covered|
|Saint Barthelemy||Sun 77% covered|
|Anguilla||Sun 77% covered|
|Saint Martin||Sun 77% covered|
|British Virgin Islands||Sun 76% covered|
Solar eclipses occur when the Sun, Moon and Earth are aligned in an almost exact straight line, with the Moon in the middle, such that the Moon passes in front of the Sun.
The Moon passes close to the Sun in the sky every month, at new moon, but because the Moon's orbit is tipped up by 5° relative to the Earth's orbit around the Sun, the alignment usually isn't exact. As a result, the Moon usually passes a few degrees to the side of the Sun.
Even when eclipses do occur, they are not visible from the whole world at once. The Moon casts a circular shadow onto the Earth, but because the Moon is much smaller than the Earth, the shadow doesn't cover the whole planet. Over time, the shadow sweeps across the Earth, so that different places see the eclipse at different times.
The eclipse path
The simulation to the right shows the path of the Moon's shadow across the Earth.
The red line shows the edge of the Moon's shadow: all places inside the red circle will see the Moon covering some part of the Sun's disk. The white contours within this show where the Moon appears to cover 20%, 40%, 60% and 80% of the Sun.
The white spot in the centre of the Moon's shadow traces out the thin eclipse track where a total eclipse will be seen.
From Ashburn (select a different location), the percentage of the Sun's disk covered by the Moon will proceed as follows:
As seen from any given location, this total eclipse will last for a maximum of 2 minutes.
Below, the path of the Moon's shadow is reprojected onto a flat map of the world. As before, the red contour shows the edge of the Moon's shadow, and encloses everywhere where the eclipse can be seen. The white contours show where the Sun is 20%, 40%, 60% and 80% covered.
The map below shows a still image mapping the maximum extent of the eclipse across the world. The red contour encloses all places in which any part of the eclipse is visible.
Observing the Sun can be very dangerous if it is not done with the right equipment. The Sun is the brightest object in the sky, and looking directly at it can cause permanent eye damage within seconds. Viewing it through any optical instrument – even a pair of binoculars or the finderscope on the side of your telescope – can cause instant and permanent blindness.
If you have any doubts about whether your equipment is safe, it is best not to risk using it. By far the safest thing to do is to go along to a public observing event. Many astronomical societies are likely to be hosting observing events on the day, and they'll be sure to welcome newcomers. You may meet some new people at the same time as seeing the transit.
Many astronomy suppliers sell special special filters which are made for safe solar viewing. These include aluminised mylar filters, or black polymer filters, identified as suitable for direct viewing of the Sun. Check that the filter has a CE mark, and a statement that it conforms to European Community Directive 89/686/EEC. Alternatively, you can use a welder's glass rated at No. 14 or higher. Always read the manufacturer's instructions carefully.
Never attempt to make your own filter. In addition to visible light, the Sun also produces prodigious amounts of infrared and ultraviolet radiation which cannot be seen yet can still damage your eye. Even if a homebrew filter appears adequate, it may allow this unseen radiation to pass.
Projecting an image of the Sun
Another safe way to view solar eclipses is to buy a purpose-built solar projection box.
These typically consist of a cardboard box with a small lens on one side. They project an enlarged image of the Sun onto a white cardboard sheet inside the box. Once the transit is over, they're also great for observing sunspots. They are safe to use, quick to set up, and ideal for use with children and groups.
This eclipse is a member of Saros series 145. The position of the Sun at the moment of greatest eclipse will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 21 August 2017|
29 days old
All times shown in EDT.
Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.
The simulations above were derived from the DE405 ephemeris published by the Jet Propulsion Laboratory (JPL). The position of the Moon's shadow is superimposed on maps of the world taken from the NASA Visible Earth project.
The list of countries from which the eclipse is visible was computed on the basis of shape files available from DIVA-GIS.
Additional information was taken from:
Espanak, F., & Meeus, J., Five Millennium Canon of Solar Eclipses: -1999 to +3000, NASA Technical Publication TP-2006-214141 (2006)
You may embed the animations and images above in your own website. They are licensed under the Creative Commons Attribution 3.0 Unported license, which allows you to copy and/or modify them, so long as you credit In-The-Sky.org.
|14 Aug 2017, 21:16 EDT||– Moon at Last Quarter|
|21 Aug 2017, 14:31 EDT||– New Moon|
|29 Aug 2017, 04:14 EDT||– Moon at First Quarter|
|06 Sep 2017, 03:04 EDT||– Full Moon|
© Lutfar Rahman Nirjhar. Image taken in July 2009.