September Night Skies over Tanzania - Two Eclipses and the Dhul-Hajj Crescent

September Night Skies over Tanzania - Two Eclipses and the Dhul-Hajj Crescent


Our majestic Moon determines the fate of three major events this month, a Partial Solar Eclipse, Idd ul Adha/Hajj, and a Total Lunar Eclipse.

 

 The first event, a partial solar eclipse occurs over the Antarctic on September 13.  A solar eclipse occurs when the Moon aligns exactly between the Earth and the Sun hence cutting off all or part of the sunlight.  Though this eclipse will not be visible from Tanzania, solar eclipses generate great interest among scientist for their ability to provide a natural laboratory to measure effects when a considerable portion of the Sun’s energy is suddenly cut off.  The author will be joining an enthusiastic eclipse team led by Professor Jay Pasachoff, a renowned solar eclipse scientist, to observe the maximum eclipse from the southernmost tip of Africa at Cape Agulhas 250 kilometers southeast of Cape Town. This will be Prof Pasachoff’s 62nd solar eclipse expedition, which the author hopes to use to gain useful experiences to conduct similar eclipse measurements during our own major annular solar eclipse next year, on 1st September, 2016, that will be centered over southern Tanzania

 

Solar eclipses occur when the Moon is in alignment with Earth and Sun.  This marks the exact moment of New Moon during which the night side of the Moon is facing us, hence we cannot seen the New Moon. Islamic months follow the lunar cycle following observations of the First Crescent, which can only be seen when the Moon has moved sufficiently away from its alignment with Earth and Sun.  This allows a small portion of the sunlit portion of the Moon to become visible to observers on Earth.  Such a condition usually requires the Moon to be al least 10 degrees away from the Sun-Earth line, hence the First Crescent this month cannot be seen on 13th. By the following day, 14th, a thin (1.5%) crescent will be 13 degrees above the horizon and can be visible if the sky is clear in the west.  This year’s First Crescent will mark the beginning of the month of Dhul Hajj, ten days after which is marked the Idd ul Hajj after the completion of the pilgrimage to Macca of millions of Muslims from around the world.  Since the Antarctic solar eclipse occurs on 13th September, the First Crescent will be expected to be visible the next day, 14 September and counting 10 days after that, the Idd ul Hajj can be expected to be celebrated on 24 September, 2015.

 

The third event determined by the Moon is the September 28 Total Lunar Eclipse during Full Moon. Having just caused a solar eclipse on 13th September, the magnificent Moon will still be in similar Earth-Sun alignment and will result in a lunar eclipse.  Lunar eclipses generally follow 15 days after the a solar eclipse because during this time the Moon shifts moves in its orbit to be in a Full Moon position when the Earth comes  between the Sun and the Moon, causing the Earth’s shadow to fall directly on to the Moon. This causes the lunar eclipse.  This month’s Total Lunar Eclipse will be visible in Tanzania and will be seen in the west, just before dawn/sunrise of Monday 28 September when the Moon is setting below the western horizon.  The partial phase will begin at 04:07 AM when the Moon will be 30 degrees above the western horizon with the Earth’s shadow starting from the upper edge of the Moon.  A black shadow will gradually slide over the face of the Moon which will be covered up by 05:11 AM by which time the Moon will be lower in the west, 15 degrees above the horizon. 

 

Once the Moon is fully covered its colour changes to brown or orange due to refracted light  from the Earth’s atmosphere.  The colour in fact can show us how much pollution is there in our Earth’s atmosphere, with a clean atmosphere producing brilliant brown or orange colours while a polluted atmosphere produces a greying colour.  Watch out the colour of the Moon during this eclipse.  If the horizon sky is not cloudy, we can expect to see the maximum darkness at 05:47 AM when the Moon will be very low, only 6 degrees above the west horizon.  We will not be able to see the remaining progress of the eclipse because the Moon will have set below the horizon and the Sun will have risen by 6:20 AM.  Observers in the west of Tanzania in Kigoma and Bukoba will see a little more of the full eclipse than those in Dar es Salaam and Zanzibar.  The whole period of the eclipse including the invisible penumbral parts occur between 03:11 AM and 08:23 AM.

 

The next total lunar eclipse will not occur over Tanzania for another three years until 27 July 2018 so better make the most of this opportunity to wake up very early on to behold the golden Moon. Check out more descriptions of eclipses on on http://www.astronomyintanzania.or.tz

 

 

 

We are once again upon the equinox with 23rd September as the day of Equinox.  The length of day and night will be exactly equal (12 hours) throughout the world.  The Sun will be exactly overhead at midday for places on the equator. 

 

For us in Tanzania who are between 2 and 11 degrees south of the equator the Sun is overhead twice each year, the first before the March equinox, between February 23 and March 18 and the second between September 26 and October 22 after the September equinox.  It is interesting to look out for the exactly overhead sun during this period because shadows of all vertical objects disappear below the object and you cannot see them. If you stand in the midday Sun on these two days you will not be able to see your own shadow.  Go out and find out which day during the September 26 and October 22 period and find out on which day your shadow disappears at midday.  Learn more about the zero shadow day from http://planetcalc.com/1875/ and http://www.iiap.res.in/iya09/VPwkshop/talks/RugvedPund.pdf

 

Among the planets we shall see a good array of them in the evening and pre-dawn skies. Saturn continues to occupy a high position, close to the tentacles of Scorpio, 60 degrees above the western horizon at sunset and visible until 10 pm lower in the west.  A beautifully crescent Moon will be close to Saturn on 18 and  19 September with the crescent cradling the Saturn on the first day and then moving past the planet on the other side on the second.  By 20th the Moon will be half shape which is ideal for viewing its craters through a telescope along its day/night line where long shadows vividly highlight the depth of the craters.

 

Mercury is still high at 20 degrees above the west horizon at sunset and is fast moving down and will be lost in the Sun’s glare by 25th.  On 15th September Mercury will be in a right angled triangle with a beautifully thin crescent Moon to its right and above them will be Spica the bright star of Virgo. Through a telescope, Mercury has a crescent shape now.


All the other visible planets are on the dawn/sunrise side towards the East. Venus shines brightly, dominating the morning sky 30 degrees above the east horizon at sunrise.  Jupiter will become visible and shine brightly with Venus from 9th September onwards.  On 10 September a thin crescent Moon will be close to Venus, while on 11th the crescent will be between Venus and Jupiter while on 12 September the crescent Moon will be close to Jupiter.

 

Jupiter is shifting up in the sky and by 25th of next month Venus and Jupiter join up in the eastern sky at 40 degrees elevation to be extremely close within one degree.

 

 

The Milky Way stretches as a band of numerous stars across the middle of the evening sky, passing through the Southern Cross in the southwest, through Sagittarius overhead, to Cygnus in the northeast.  The portion of the Milky Way close to Sagittarius appears as a cloud that is not a real cloud but nebulae of dense interstellar matter that is hiding from our view a powerhouse that is a supermassive blackhole at the center of the Milky Way galaxy.

 

The Scorpio constellation can be clearly identified by its namesake the scorpion and can be seen high in the western sky.  The eastern sky has two “birds”; one to the northeast, where you will see the Cygnus with its body and wings making a wide cross, while in the southeast you will see the smaller bird Grus with its head twisted sideways and its brightest star Alnair (J).

 

Try to become familiar with the brightest stars by their names and relative locations. Eight of the top twenty brightest stars in the sky are visible in our evening skies.  The stars marked A to H are listed here with their names and its rank in brightness.  A – Formalhaut (18th), B – Altair (12th), C – Deneb (19th), D – Vega (5th), E – Antares (16th), F – Alpha Centauri (4th), G – Arcturus (3th), H – Spica (15th).  The other less brighter stars are: Alnair (J), Peacock (K), Kaus (L), Girtab (M), Shaula (N), Atria (P), and Hadar or Beta Centauri (R).  The asterism marked S on the map is the Square of Pegasus, which is quite noticeable and can guide you to Andromeda Galaxy marked T on the map and rising in the north east at 8 pm.  This galaxy is 2 million light years away and can be seen as an oval cloudy patch in dark skies, making it the most distant object that can be seen by our eyes directly without a telescope. Star with brightest stars A to H and use those to find your way around the sky.

 

There will be an opportunity to see the International Space Station over three days from 26 to 28 September but the best view will be on 28th when it will cut across the sky from 6:31 PM to 6:40 PM moving from southwest to northeast horizons.  The Sun will have just set at 6:18 PM so the sky will be still bright but the ISS is bright enough to be seen in the twilight.



 



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