Forecast for August 2013
The Moon
New 6th 05:14
-- 20:05
First Quarter 14th 14:39
-- 23:29 Full 21st 20:01 -- 06:30
Last Quarter 28th 23:23 -- 14:51
During this period of the
year, the Milky Way can be seen directly across the zenith, though it is the
part away from the centre of the galaxy, and fainter than the centre of the galaxy, but the Cassiopeia to Aquila part is very busy with stars, clusters, nebulosity and planetary nebulae.
Planets
Mercury rises on the 1st
of the month at 4am in lightening dawn twilight, a 7 arcsec disc of mag 0,
showing only 45% of its disc. 11° to the upper right is Jupiter to help find
it, and between them is Mars at mag 1.6, and to the left 9° away is the “Comet
of the Decade”, if it turns out so, ISON, but at mag 13 it will be invisible.
On the morning of the 5th a crescent Moon will rise with them,
making a pretty picture for wide field photographers. Mercury will be at mag
-0.5 showing a 60% phase. It will appear to hold the same position for several
days, but in fact is hastening towards the Sun, so making it more difficult to
find in brightening twilight, the stars will be moving a little each day to the
upper right. From about the 17th, Mercury will be too close to the
Sun to seek with optical aid.
Venus is an evening object this month at mag -3.9, with an
83% illuminated disc of 13 arcsec, so should be very easy to find on the 1st,
as it sets in the WNW at 10pm, an hour after the Sun. On the 9th it
will be setting in company with a very thin crescent Moon below it. You’ll have
to catch it before the Moon sets of course for a decent photograph, but Venus
will set at 9:35pm, the Moon having down before that. It will continue to hold
its position, setting about an hour or less after the Sun, and by the end of
the month will be mag -4.0 and present a 74% illuminated disc of 15 arcsec.
Mars will rise on the 1st, at 3am
into a lightening sky, well before the Sun, as a 4 arcsec disc at mag 1.6, 20
mins after much brighter Jupiter. It will pretty much hold its position during
August, relative to the horizon, but in fact will be moving quite speedily
relatively to the stars, moving from Gemini into Cancer during the month. It
will also remain unchanged in size and brightness, but fortunately, as the
month progresses, it will be rising into a darker sky. It has been on the far
side of the Sun this year but will come into its own this coming April.
Jupiter will rise at 2:45am on the 1st,
as a mag -2.0 disc of 33 arcsec, but the sky is lightening so not much detail
to be seen yet. From about the 15th it will be higher up and in
darker skies and a little larger too so begins to become more interesting. On
the 4th, at 4am, it will be part of a triangle of Mars, Jupiter and a
thin crescent Moon about 6° from each other, with Mercury a little way off to
the left. At the end of the month Jupiter will be at mag -2.1 with a disc of 35
arcsec, rising at 1:15am and will be in dark skies for the next 3 hours.
However on the 31st it will have a fat crescent Moon 8° away as it
moves across the sky.
Saturn is an evening object this month, but
only just, as it is setting in darkening twilight on the 1st, at
11:30pm, and getting closer and closer to the horizon as the nights go by. It
sets at 9:30pm at the end of the month but as the nights are getting darker it
is likely to be setting in similar skies all month. But all this is so close to
the horizon that it makes little improvement and little detail is likely to be
seen.
Uranus will rise on the 1st, about
midday and set at 11:30pm. It will be due south at dusk, so we get half the
night to observe. It will be mag 5.9 and 3 arcsec in diameter. A tiny disc to
seek in the lowering dusk, so wait for it to get fully dark before trying. It
will always be difficult unless you use a large goto instrument. The situation
worsens as the month progresses, giving us less time to observe, as it will set
on the 31st at 9:45pm having been available from dusk, about 5:30pm.
Neptune will be even more difficult, available
on the 1st from dusk, about 5pm, till it sets at 8:30pm. An even
smaller disc of 2 arcsec and mag 7.9. Drawing closer to the Sun like an inner
planet, as the month progresses. At the end of the month it will be visible
from late dusk, about 5:30pm till it sets at 6:30pm. Hardly worth the effort as
most of that time it will be low in the murky sky too.
Meteor Showers. This is
the month of the Perseids, peaking this year on the 11th at 6am. Up to 100 hourly at the Zenith is possible.
As the radiant rises in the east, the Moon will be setting on the other of the
sky and be out of the way by dusk on the 11th.
Comets. As mentioned
above we have ISON coming towards us, slowly, but it’s still very faint. The
last good one, PANSTARRS, is in Bootes making its way towards Beta Bootis,
which is the top star of the Bootis kite. It’ll get there on the 29th,
unhappily fading during the month from mag 12 to mag 13, and beyond the range
of visual equipment unless you have a “big Dob”. 29P/Schwassmann-Wachmann has
had an outburst worth looking for, but it’s in the same part of the sky as
Saturn, setting soon after the Sun and till then is in murky twilight, so not
really a good prospect.
The latest comets from a
few years ago, are listed there. Click on one for the ephemeris. If you like
it, download it as a KML file by clicking on the KML file link. Then click on
it on your desktop, which is where it’ll land when it gets to your machine.
Click on it there and it will ask you to run google earth then to change it to
google sky and the path of the comet will be drawn across the google sky for
you. Don’t bother with any that show a mag number larger than 7 or 8. Most on
the list are more than 15, which is very faint indeed.