by Anne Holt Sunrise 1st: 05.24 31st: 06.16 Sunset 1st: 21.05 31st: 20.01 Astronomical darkness 1st: 00.38 to 02.02 31st: 22.14 to 04.04 New Moon: 11th at 10.57 Full Moon: 26th at 15.26 Lunar perigee: 10th at 19.06 Lunar apogee: 23rd at 12.25 August's
full Moon is known as the Sturgeon Moon because these fish in the
American Great Lakes are said to be easiest to catch at this time. Other
names are the Green Corn Moon and the Grain Moon. Some North Americans
call it the Red Moon as it sometimes appears this colour when it rises
through the summer haze. Highlights Nights
are getting longer by almost 4 minutes each day and we have increasing
amounts of astronomical darkness during August - 2 and three quarter
hours on 1st and nearly 6 hours on the night of 31st August/1st Sept. The
new Moon on 11th is a Supermoon, occurring close to Lunar perigee. Of
course a new Moon can't be seen but the thin waning crescents, rising at
02.55 on the morning of 9th and at 04.05 on the 10th, should appear
larger than usual. There is a small partial eclipse on the
morning of 11th but it is only visible from the far north of Scotland,
Orkney, Fair Isle and Shetland. From Thurso on the coast of northern
Scotland, the edge of the Moon will cross the face of the Sun between
09.30 and 10.00. From Lerwick, in Shetland, the eclipse will be
slightly longer - 09.30 to 10.15. However, it will be a very small
'bite' out of the Sun the maximimum is only 2.5% when seen from the
most northerly part of the Shetland Isles. And, of course, we have the year's best meteor shower, the Perseids, free this year from Moon interference. Constellations When it finally gets dark enough, the Milky Way is now at its best. From a dark sky site it can be seen stretching right across the sky and down to the southern horizon, passing almost overhead around midnight. The Plough and its host constellation Ursa Major are now very low in the Northern sky which means that the W asterism of Cassiopeia is riding high in the south east and very easy to spot. Pegasus and Andromeda are now well above the horizon for most of the night and Perseus, followed by Auriga, are rising soon after midnight. Planets Mercury: in Libra, mag 2.9. Not
visible for most of August. On 1st it sets a few minutes before the
Sun and is separated from it by only 14 degrees. The angular distance
decreases as it approaches inferior conjunction on 9th. It then becomes
a morning object, in Cancer, but is still too low to be seen until the
last few days of the month. On 20th it will be at mag 1.4 and be a few
degrees above the horizon at 05.15. On 26th it reaches greatest western
elongation, 18.3 degrees from the Sun but still only 8 degrees above
the horizon at dawn - though brighter at mag - 0.1. On 30th it moves
into Leo and on 31st it rises at 04.25, reaching 8 degrees above the
eastern horizon at 05.46, half an hour before sunrise, and brighter at
mag -0.7. Venus: in Leo, mag -4.2. Could
be seen in early August, on 1st it sets at 22.22, about 90 minutes
after sunset. It is only 7 degrees above the horizon at dusk but should
be visible, given an unobstructed view, as it is so bright. It moves
into Virgo on 2nd. The angle of the ecliptic is decreasing so the
planet is getting lower in the sky, even though it reaches greatest
eastern elongation on 17th. On this day it is 49.5 degrees from the Sun
but only 4 degrees above the western horizon at dusk, setting about an
hour after sunset. On 31st it will have brightened to mag -4.4 but
will be only 3 degrees above the horizon as the sky begins to darken,
setting about 45 minutes after the Sun. Mars: in Capricorn, mag -2.8. Still
very bright, and large when seen through a scope, but rather low in the
sky. On 1st it culminates at 00.57, only 10 degrees above the southern
horizon. In the first few days of August it's disc is 24 arcseconds in
diameter, however it will be difficult to see, or image, much detail
through a scope - not only is it low but there are currently huge dust
storms blowing across the surface. It fades slightly during the month,
on 23rd, when the 82% lit Moon passes 6 degrees to the north, Mars will
be at mag -2.3. Its apparent motion is retrograde for most of the month
but after 28th it resumes prograde, or direct, motion appearing to move
eastwards against the background stars. On 31st it culminates at 22.36,
10 degrees above the southern horizon It sets at 01.59 and will have
faded to mag -2.1. Jupiter: in Libra, mag -2.1. Quite
low in the west as the sky darkens now. On 1st it is only 15 degrees
above the horizon at 21.30, setting at 23.35. On 17th the 45% lit
Moon passes about 5 degrees north of the planet. By month end it will
have faded slightly to mag -2.0, be only 11 degrees in the SW a few
minutes before 20.30 as the sky darkens, and set at 22.00. Saturn: in Sagittarius, mag 0.2. An
early evening object, not easily seen as it is currently sitting north
of the teapot asterism, where the Milky Way is rather bright. It is
also quite low - on 1st it is only 12 degrees above the southern horizon
as the sky darkens, just before 22.00. It culminates, a degree higher,
at 22.41 and sets at 02.33. On 31st it culminates only half an hour
after sunset and may be seen, 13 degrees above the southern horizon,
just before 21.00. It sets at 00.30 and will have faded to mag 0.4. Uranus: in Aries, mag 5.8. On
1st it rises at 23.17 and reaches 33 degrees in the SE before the sky
begins to brighten. It is currently the only planet reaching a good
altitude. On 4th it is about 4 degrees north of the third quarter
Moon. It gets even better as the month progresses and on 31st it
culminates at 04.32, 48 degrees above the southern horizon, it will also
be marginally brighter at mag 5.7. Because it is so well positioned,
high in the sky at the moment, it could possibly be seen with the naked
eye from a dark sky site - with the usual proviso that they eye in
question must have 20/20 vision and know exactly where to look. Though
I've yet to meet anyone who has seen it without any optical aid. It
should be an easy binocular target, and a decent amateur scope will show a
small blue/green disc. A much larger scope will be needed to show any
markings. Neptune: in Aquarius, mag 7.8. Reasonably
high in the sky, though lower than Uranus. On 1st it rises at 22.07
and reaches 29 degrees in the SE before the sky begins to brighten. On
27th the just past full Moon passes about 6 degrees to the SE just
before midnight. By month end the planet culminates at 01.38, 29
degrees above the southern horizon. It could possibly be seen, through
decent binoculars, in the late evening in the second part of the month -
though probably not from Manchester. A good amateur scope should show
its bright blue disc. Minor planets Ceres and Pluto are too low to be easily spotted this month. Eris, Haumea and Makemake are possible targets for keen amateur photographers with good equipment. Eris: in Cetus, mag 18.8. On
1st it rises at 02.22 and is 23 degrees above the horizon at dawn. Its
position improves during the month, on 31st it rises at 22.21 and
culminates at 04.17, 34 degrees above the southern horizon. Haumea: in Bootes, mag 17.4. Starts
the month 27 degrees above the western horizon as the sky darkens,
setting at 02.21. By 31st it is 23 degrees above the horizon at dusk,
setting not long after midnight. Makemake: in Coma Berenices, mag 17.2. Setting
about 15 minutes before Haumea throughout August, but lower in the sky -
22 degrees just before dawn on 1st, 18 degrees on 31st. For more information, including exact positions on any day see: https://in-the-sky.org/ephemeris.php (for minor planets, look under asteroids) Meteor Showers One (very) major shower, this month. The Perseids,
active July 13th to August 26th. Peak on the night of 12th/13th but
good rates can usually be seen a day or so either side of this. ZHR at
peak is given as 100 but this is under ideal conditions - from a dark
sky site with the radiant directly overhead. Usual rates under dark
skies more likely to be in the region of 50 to 75, and as low as 10 from
a light polluted urban area. Best seen after midnight (01.00 BST) when
the radiant is high in the sky, but it is worth looking earlier as the
shower sometimes includes Earth grazers - rare, slow moving meteors
streaking across the horizon leaving bright persistent trails, which are
occasionally seen when the radiant is very low in the sky. The
Perseids happen when Earth passes through debris left by comet
109P/Swift Tuttle. This year the Moon is out of the way, it sets at
21.32 on 12th. All we need is for clouds to stay out of the way, as well. Minor Showers Kappa
Cygnids. active 3rd to 25th, peak 18th. However, this shower may have
altered and be active between 6th and 18th with a peak on 14th. ZHR 5,
but sometimes many more. According to the IMO this shower does not
always behave as it is supposed to. They are slow moving, often very
bright, meteors, parent comet unknown. The Moon sets before midnight on
both the possible peak dates. Aurigids,
active August 28th to Sept 5th, peak 31st/Sept 1st. ZHR 6, again
sometimes more, but not predicted for this year. These are bright, slow
moving meteors. 80% Moon rises at 22.13, so will interfere. There
are a couple of showers whose peak is actually at the end of July, but
which usually have reasonable rates for a couple of days after, so might
be worth looking on the first couple of days of August. Alpha
Capricornids: active to August 15th, ZHR 5. Slow moving, yellow
tinged meteors often leaving trails. Moon rises soon after 23.00 on
1st, but the shower often includes fireballs which may be visible
despite this. Southern Delta Aquariids, active to August 15th. medium paced, faint meteors. so more likely to be washed out by moonlight. Comets In August we have a couple of comets which may be visible in binoculars. 21P/Giacobini-Zinner. Currently
circumpolar. Starts the month at about mag 9 (sources vary - there's a
surprise) moving from Cassiopeia into Draco. Back into Cassiopeia mid
month before moving through Camelopardalis and ending the month in
Auriga, heading towards Capella, when it is predicted to reach mag 7.2.
Or maybe even brighter. PanSTARRS (2017S3) Visible
in the morning sky in the first few days of August. Starts the month in
Auriga, then quickly moves into Gemini and getting too low to be seen
before dawn. The magnitude increased rapidly during July, from 12 to
9. Starts August at mag 8 and could brighten to 7. More info on www.cometwatch.co.uk comet positions also given in in-the-sky.org |