Eclipses in 2017
There are four eclipses in 2017, two each of the Sun and moon. Four is the minimum number of eclipses there can be in a year.
The first solar eclipse on February 26 is annular with a path starting at sunrise in the south Pacific Ocean well west of Southern Chile. Its path takes it over Southern Chile and Argentina before heading off across the Atlantic Ocean towards Africa. It make landfall again in southern Angola near the time of sunset. The eclipse ends at sunset in the southern-most part of the Congo Republic near its border with Zambia. The second solar eclipse is total, it starts at sunrise in the northern Pacific and crosses the continental U.S.A. from Oregon to South Carolina. The eclipse ends at sunset in the Atlantic west of Africa. No part of either solar eclipse is visible from New Zealand.
By contrast to the solar eclipses, the two lunar eclipses are very paltry affairs. Neither are total; the first on February 11 is penumbral, the second on August 7 is partial. The lunar eclipse on February 11 takes place 2 weeks before the annular eclipse of the Sun. It is entirely a penumbral event, with the Earth only obscuring part of the solar disk as seen from the moon. 98.9% of the moon’s diameter will be in the penumbra while a sliver, 1.1% of the diameter wide, near the moon’s south pole, will remain in full sunlight. No part of the moon’s disk will enter the Earth’s full shadow. The entire eclipse will be best seen from Africa, Europe and the Atlantic Ocean. At the second lunar eclipse on August 7 the moon will move a little more deeply into the Earth's shadow so that at its maximum almost one-quarter of the moon’s diameter will be completely shaded from the Sun. The remaining 75% will be in the part shadow, the penumbra. In this case the southern quarter of the moon will be darkened. The remainder, still partly sunlit, will be somewhat dimmed. The start of the eclipse will be visible from New Zealand, with the moon setting after mid eclipse. Australia sees the whole of the eclipse.
More information on eclipses can be obtained at the NASA eclipse pages: http://eclipse.gsfc.nasa.gov/.
Diagrams, maps and the tables showing times of phases of lunar eclipses have been prepared using David Herald's Occult 4 program.
Viewing Eclipses of the Sun and Transits of Planets across the Sun
Whenever the Sun is to be observed safe viewing methods must be used. Any attempt to view the Sun directly could result in instant blindness.
The safest way is to project the image of the Sun onto a suitable screen. Alternatively a suitable, specially designed, Solar filter may be placed in front of the telescope.
It is not safe to use a filter at the eyepiece as the focussed heat from the Sun could shatter it. If unsure of safe methods consult your local astronomical society about suitable ways of observing Solar events.
Penumbral eclipse of the Moon 2017 February 11
At this eclipse of the moon a maximum of 98.9% of the moon’s diameter moves into the Earth’s penumbral shadow, with 1.1% remaining in full sunlight. The uneclipsed sliver will be near the moon's south pole, while the most northerly parts of the moon will be close to, but not in, the umbra. So we may expect this part of the moon to be distinctly dulled, with the surface brightening further south.
In a penumbral eclipse an observer on the moon would see part of the Sun covered by the dark Earth. In this eclipse the greatest amount covered would be seen in the north. As the observer moved south on the moon less of the Sun would be covered until in the far south no part of the very low Sun would be hidden.
As seen from the Earth the moon will be visible from northeast Canada and eastern South America, Europe. Africa and the Middle East throughout the eclipse. Changes in the moon's brightness will not be very marked. In the remainder of north and south America the moon will rise during the eclipse. As seen from much of eastern Asia, the moon will set during the eclipse, as it will from most of Indonesia. No part of the eclipse is visible from Australia, New Zealand or the western parts of the Pacific, including Japan and the Philippines.
Times of the start, maximum and end of the eclipse are shown on the diagram, which also shows the parts of the Earth from which the various stages are visible. The coloured circles at the top left shows the path of the moon (outlined and numbered 1, 4 and 7) through the penumbral part of the Earth’s shadow.
Annular eclipse of the Sun, 2017 February 26
The annular eclipse of the Sun on February 26 starts in the southern Pacific Ocean well west of Southern Chile. The Sun will rise in annular eclipse at a point about 3500 km west of the southern coast of Chile and about 1000 km south of Easter Island (I. de Pasaua). As it rises, 97.7% of the diameter of the solar disk will be covered by the moon. The width of the annular path will be 96 km and the duration of the annular eclipse 82.4 seconds.
At first the annular path will move slightly south of due east to cross the coast of Southern Chile about 18 minutes later at the I. Rivero. Inland in Chile it passes close to Coihaique and then Facundo in Argentina. By then the Sun will be 98.6% covered and the annular phase will last 64.5 seconds. The annular path leaves the east coast of Argentina close to Cape Dos Bahias some 11 minutes after it crossed the west coast.
As the path moves out across the Atlantic Ocean it swings more to the northeast. Maximum eclipse occurs well out in the Atlantic Ocean at about longitude 31° W and latitude 35° south at near local midday. At the maximum 99.2% of the solar disk will be covered by the moon, and the annular phase will last only 44 seconds. The increase of the amount of Sun covered and the consequent shortening of the annular phase are due to the Earth’s surface being closer moon when the latter is highest.
After eclipse maximum the path of the eclipse continues across the Atlantic passing well south of St Helena. It crosses the coast of Africa in southern Angola a little to the north of Mocamedes. By then the Sun will be near setting, a little way inland it will indeed set before the end of the eclipse although the annular phase will remain visible as it crosses Angola and enters the extreme south of the Congo Republic along the border with Zambia. The annular eclipse ends as the sun sets to the northwest of Lubumbashi about 3 hours 15 minutes after it started in the Pacific. At its end 97.8% of the solar disk will be covered, with the annular phase lasting 77.4 seconds.
No part of the eclipse is visible from Australia nor from New Zealand.
Partial eclipse of the Moon 2017 August 7
At this eclipse a maximum of just under 25% of the moon's diameter will be immersed in the umbral, full shadow of the Earth. In this case it will be the southern part of the moon which is darkened. The remainder of the moon will be in the penumbra, partial shadow, of the Earth. The entire eclipse is visible from the east coast of Africa central Asia except the north Indonesia and Australia except the eastern seaboard. The moon rises during the eclipse as seen from the rest of Africa, Europe and western Asia. Further east the moon will set during the eclipse as seen from much of the remainder of Asia, Indonesia and Australia. From the New Zealand the eclipse will start with the moon low to the west. All parts will see the beginning of the umbral phase, visible in its entirety from the South Island, before the moon sets.
Total eclipse of the Sun 2017 August 21
The total eclipse on August 21 starts at sunrise in the north Pacific Ocean about half way between Hawaii and the eastern most part of Siberia. The total eclipse moves eastwards to enter the U.S.A. in Oregon a little south of Portland with Salem in the path. After crossing the U.S.A. the eclipse leaves the country from South Carolina with Charleston in the path. It heads across the Atlantic Ocean towards Africa, but ends at sunset still west of the continent and to the south of the Cape Verdi Islands.
The greatest duration of totality is just over 160 seconds and occurs along a belt from south of St Louis, Missouri, to north of Nashville in Tennessee. The maximum path width of totality is 155 km.
No part of the eclipse is visible from New Zealand or Australia apart from the western coast of the latter where the eclipse starts as the Sun sets.
For a detailed map showing the path across the U.S.A. Eclipse path
The following PDFs are extended versions of the Evening Sky articles including extra charts and descriptions of additional objects of particular note in the month's sky.
The numbers on the end of the file name are the year followed by the month number.
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Observing the Leonids
November brings an increase in the meteor activity we are likely to observe from New Zealand. In the early part of the month, the 2 Taurid meteors showers are with us, although they don't usually bring about spectacular meteor displays.
The shower that has excited meteor observers over the past few years is the Leonids. Normally a reliable, yet quiet meteor shower, every 33 years or so, the orbit of the Earth in relation to the path of Comet Temple-Tuttle means the Earth passes through the denser parts of the cometary debris that follows the orbit of the comet. The years 1998-2001 were years ago identified as years when the Leonid meteor shower were likely to be spectacular. There had been some quite spectacular displays in 1933 and 1966. So we may have to wait until he early 2030s for the next spectacular display.
I observed the Leonids from Hawaii on the morning of 17 November, 1998 (Hawaiian time) from a site on the lower slopes of Mauna Kea. I could only watch around 25% of the sky at any one time, but over a three hour period, I observed around 140 Leonid meteors. If I could have observed the whole sky, and the radiant had been near the zenith, I might have seen 4 or 5 times that number.
The peak of the Leonids, in view of observations made in the last few years, appears to be very short - just a very few hours. We like to think we know where the best observing place is likely to be, but predictions have proved to be a little astray in the past.
The problem we have in New Zealand is that the radiant point, which is within the 'sickle' of Leo, rises only an hour or two before the commencement of dawn.(the further south you are, the worse it is). Thus, from New Zealand we can only observe 30% or so of the meteors that might be seen if the radiant was high in the sky.
Given that the radiant is low in the north-east, observers will need a site with a dark sky to the north and east and from there up to the zenith. Almost all the meteors will be observed some distance from the radiant point. So it is much better to look a minimum of 15-20 degrees away from that point. You will be able to identify a Leonid meteor quite easily. Note it's path in the sky, and its length. Then take the point where you first saw the meteor, and trace a path back from that point in exactly the opposite direction to which the meteor travelled, and for about the same distance as the meteor travelled. If that brings you to a point around the 'sickle' of Leo, you will have observed a Leonid.
Leonids are noted for leaving brief trains and trails, which may be visible for several seconds. One Leonid I observed left a smokey trail visible for several minutes.
So I guess all I can say is - happy meteor watching. Don't forget to wrap up warm and have a hot drink handy. If you get cold, the quality of your observing will be compromised. Meteor watching is a good group activity, so get some of your colleagues in on the exercise. If you do this, don't forget to record what part of the sky each observer was designated to look at. Very important. OK - go to it.
Next month we'll take a look at the prospects for the Geminids.
The chart shows a field of view to the north east about 1 hour before sunrise. The width of the field is about 45° and its height about 40°
The + near Regulus marks a point to the north east with an altitude of about 20° from mid South Island and about 4° higher from the central North Island. Stars to magnitude 5.5 are shown Those 3.5 or brighter are marked also have their magnitudes shown, without a decimal point.
Chart prepared with the aid of GUIDE 7.0.
Observing the Geminids in December
The Geminid Meteor shower is one of the most active of the year, sometimes surpassed only by the Perseids in intensity.
The shower peaks on the morning of 15 December in New Zealand. The Geminids don't seem to have a sharp peak like the Leonids, and observations can be made for a week either side of the peak.
At it's height, the Geminids have a zenith hourly rate of about 80 meteors per hour. So, if for you the radiant was at the zenith, and you could observe the whole sky at once, you might expect to see 80 meteors an hour.
Alas, in New Zealand, the radiant is low. In fact it lies just a degree or two to the left of, and slightly below, Castor. So, in New Zealand we effectivly lose out on seeing 50% of the meteors before we start. But it is still a shower worth looking at. I have found from when I lived in Auckland, and if it was fine, seeing a dozen or more Geminids an hour around the peak was quite normal. And of course one cannot observe all the sky at once. Geminids are inclined to leave good trains, and some of those meteors travel long distances. One I observed appeared first near Sirius, and travelled overhead and a long way towards the southern horizon. Remember, meteors do not appear at the radiant, unless they are heading straight for you, but generally tens of degrees from it.
The best time to look for Geminids is any time after about 1 or 2 am through until dawn. Gemini will be approaching north. I would suggest you look for Geminids streaking through the sky in the region of Orion and the area of sky to the right of Orion. Make sure you have a dark sky from northwest sound to east, and at least up to the zenith. Keep glow from city lights to the south of you.
Most meteor showers are associated with cometary debris travelling in the orbit of the comets. The Geminids are a bit different. The appear to be travelling in the same orbit as Apollo asteroid 3200 Phaethon. Is this an asteroid that perhaps was once surrounded by and icy snowball of cometary matter?
Chart of Stars near the Geminid radiant, west to Orion.
The chart shows a field of view to the north about an hour and a half before sunrise in mid December. From the mid South Island of New Zealand, the other pair of the twins, Pollux (just above Castor) will have an altitude of about 20° and be nearly due north. For observers further north, Pollux will be a little higher.
In 2011 the moon is going to hinder observation of the meteors. On the morning of December 15, the moon will be only a little past full, 84% lit and about 26° from the radiant, so is likely to reduce the number of meteors visible.
For 2012 the moon is favourable, new moon is on December 13.
Observing the Orionid Meteor Shower
The Orionid Meteor shower peaks around 21-22 October each year. This is one of the two meteor showers associated with Comet Halley, the other being the Eta Aquairids, visible early May.
The radiant point for the Orionids is a little below, and to the right of, Betelgeuse. So it is not a high radiant for NZ observers. Orionids tend to travel quite long distances, and often leave trains, which can sometimes be visible for several seconds.
The Orionids are not a rich shower, and if you see 10 an hour from our latitude, that's good. It is definitely more favourable viewing them from the northern tropics e.g. Hawaii. But, give it a go anyway.
It is best to have a good, dark sky to the north and overhead. Don't look at the radiant area, but at least 15-20 degrees away (see notes on this in the Leonid meteors). From our latitudes, the best area of the sky to watch is the upper part of Orion and higher, Taurus, and the area of sky to the right of Canis Minor.
Betelgeuse rises about midnight, NZ time. At about 4.30 am Aldebaran in Taurus, Betelgeuse and Procyon, in Canis Minor form an arc from north to north east as seen from New Zealand.