OBSERVING GUIDE
(Please note all times are BST and are based on an observing location of Belfast and covers the month of September)
The Sun
At the start of the month the Sun rises at 06:30 and sets at 20:15. By the end of the month, it rises at 07:25 and sets at 19:00.
The Planets
This month sees a planetary conjunction of
Mercury,
Venus and
Mars. Given the ecliptic problems, you may want to try and observe this during daylight hours. On the 11th and 12th of the month,
Venus lies due South at 14:30 at an altitude of thirty degrees. Using a small telescope
Mars should lie less than a degree to the South of
Venus with
Mercury within four degrees to the South of
Venus.
HOWEVER the Sun will be up and every care should be taken if attempting this. You could try standing with a wall or fence to the West (your right), so that it blocks the Sun and you’re standing in its shadow.
Mercury is at greatest eastern elongation on the 11th. However despite this it is not well placed for observation this month due to the shallow angle the ecliptic makes with the western horizon at sunset. This has the effect that the planets appearing in the West after sunset are very low in the sky. It is at inferior conjunction next month, so the best time to observe the planet is at the start of the month when it is at its brightest at mag +0.0 and highest in the sky after sunset. However even at the start of the month, it sets less than half an hour after the Sun at 20:40.
Venus is an evening object this month; however it is not well placed for observation this month as it also suffers from the ecliptic problem outlined above. It set less than an hour after the Sun during the entire month with set times of 20:55 at the start of the month and 19:50 by months end.
Mars is lost to the evening twilight this month. However it may be visible during daylight hours (see above).
Jupiter can be found in Sagittarius. At the start of the month, it rises during daylight hours and sets at 01:15. By month’s end, it sets at 23:20. It fades from mag -2.5 to mag -2.3 during the month.
Saturn is at conjunction on the 4th and then becomes a morning object. By mid-month it rises an hour before the Sun at 06:00 and by months end, it rises at 05:10, over two hours before the Sun. It can be found in Leo and is mag +1.0 by months end.
Uranus can be found in Aquarius and is at opposition on the 13th. At the start of the month, it rises at 20:30 and by month’s end it rises during daylight hours and sets at 05:50. It is just within naked eye visibility and maintains its brightness at mag +5.7 during the month. It can be located within four degrees to the North-East of Phi Aquarii.
Neptune can be found in Capricornus. At the start of the month, it sets at 05:00 and by month’s end it sets at 03:00. The planet lies to the North of Gamma Capricorni and to the West of three closely grouped stars 42, 44 and 45 Capricorni. It fades from mag +7.8 to mag +7.9 during the month.
The Moon
The first quarter moon is on the 7th with the full moon on the 15th. As this is the closest full moon to the autumn equinox, it is known as the Harvest moon and rises on the 15th at 19:20. The last quarter moon is on the 22nd with the new moon on the 29th.
On the evening of the 9th, a 70% illuminated waxing gibbous moon lies four degrees to the South of
Jupiter.
On the morning of the 13th, there is a lunar occultation with the 93% illuminated waxing gibbous moon passing in front of
Neptune. This happens low in the West with the moon thirteen degrees above the horizon at around 02:00.
Neptune will lie a degree to the North-East of the moon. At around 03:00, the planet lies half a degree from the center of the lunar disc and over the next thirty minutes, the moon closes in and covers
Neptune.
On the evening of the 14th/morning of the 15th, a 99% illuminated waxing gibbous moon lies to the West of
Uranus.
On the morning of the 20th, there is a partial occultation of the
Pleiades by a 73% illuminated waning gibbous moon from 02:30 onwards.
On the morning of the 22nd, a 51% illuminated waning gibbous moon lies four degrees to the North-West of the open cluster
M35.
On the morning of the 25th, a 20% illuminated waning crescent moon lies to the East of
M44 – The Beehive Cluster. Moonrise is at 02:00.
The mornings between the 25th and 28th offer a good chance to observe an old lunar crescent. The morning of the 25th is discussed above. The next morning, a 10% illuminated waning crescent moon rises at 03:30 and lies close to
Regulus (Alpha Leonis) to the South of the star. On the morning of the 27th, a 5% illuminated waning crescent moon rises at 04:55, roughly half an hour before twilight begins with
Saturn lying close by to the North. Finally on the morning of the 28th, the 1% illuminated waning crescent moon rises at 06:20, roughly an hour before sunrise to the East of
Saturn. Give the moon maybe half an hour to become visible and see if you can spot an old lunar crescent just 27 hours before new moon, but be careful and watch for sunrise.
Meteors
The ZHR or Zenithal Hourly Rate is the number of meteors an observer would see in one hour under a clear, dark sky with a limiting apparent magnitude of 6.5 and if the radiant of the shower were in the zenith. The rate that can effectively be seen is nearly always lower and decreases as the radiant is closer to the horizon. The Zenith is the overhead point in the sky for an observer. The radiant is the point in the sky, from which (to a planetary observer) meteors appear to originate, i.e. the Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus.
This is a month of minor showers. The first one is the
Piscids. It has two peaks on the 8th and the 21st. The ZHR’s for the two peaks are 10 and 5 respectively. Lunar conditions for the first peak of the shower are favourable with a 62% illuminated waxing gibbous moon in Sagittarius setting at 23:10 on the evening of the 8th. For the second peak, lunar conditions are less favourable with a 53% illuminated waning gibbous moon in Auriga rising at 21:50. The
September Perseids peak on the 9th with a ZHR of 5. Lunar conditions for this peak are favourable with a 71% illuminated waxing gibbous moon in Sagittarius setting at 00:20 on the morning of the 10th. The
Delta Aurigids peak on the 28th with a ZHR of 3. Lunar conditions for this shower are excellent with a moonless evening on the 28th.
There are also four additional showers all of which are predicted to have low ZHRs. The
Gamma Aquarids which peak on the 7th, the
Alpha Triangulids which peak on the 11th, the
Eta Draconids which peak on the 12th and the
Gamma Piscids which peak on the 23rd. Lunar conditions for the above showers are as follows: the
Gamma Aquarids – excellent conditions with a 52% illuminated waxing crescent moon in Scorpius setting at 22:15 on the evening of the 7th; the
Alpha Triangulids – less than favourable with a 87% illuminated waxing gibbous moon in Capricornus setting at 02:55 on the morning of the 12th; the
Eta Draconids – less than favourable with a 93% illuminated waxing gibbous moon in Capricornus setting at 04:15 on the morning of the 13th and finally the
Gamma Piscids – favourable with a 29% illuminated waning crescent moon in Gemini rising at 00:30 on the morning of the 24th.
Comets
Comet 17/P Holmes is visible during September as a morning comet low in the East in Cancer. Its situation improves as the month goes on. Current predictions estimate its brightness at mag +7.5 with it expected to slowly fade.
C/2007 W1 Boattini moves out of Aries and passes into Pisces during September. Its brightness is currently estimated at mag +9.5 and is predicted to slowly fade.
Up to date information and finder charts for comets can be found at
www.aerith.net
and
cometchasing.skyhound.com
Deep Sky
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. Check out the constellation Canes Venatici with several galaxies including M51 - the Whirlpool Galaxy and M63 - the Sunflower Galaxy. In Hercules, two globular clusters – M92 and the excellent M13 can be observed and in Lyra – M57 – The Ring Nebula can be observed. In Vulpecula – M27 – The Dumbbell Nebula can be found. In Andromeda, M31 – The Andromeda galaxy can be observed along with its satellite galaxies M32 and M110. In Perseus, there is the open cluster M34 and the excellent Double Cluster – NGC 869 and 884. In Triangulum, there is the galaxy M33. Finally Auriga is reappearing with its three open clusters M36, M37 and M38 as is Taurus with the excellent Pleiades – M45.
For further observing information, check out
www.eaas.co.uk/stargazers.html
General Notes
Always keep an eye out for
Aurorae. Check out
www.stronge.org.uk/spaceweather.html
for the most up-to-date information on the
aurorae. The autumn equinox is on the 22nd which sees the end of summer and the beginning of autumn. This is the day where the length of day and night are the same and after this the night will take over cumulating with the shortest day of the year on the winter solstice in December.
Other interesting naked eye phenomena to look out for include the
Zodiacal Light and the
Gegenschein. Both are caused by sunlight reflecting off dust particles which are present in the solar system. The
Zodiacal Light can be seen in the West after evening twilight has disappeared or in the East before the morning twilight. The best time of year to see the phenomenon is late-Feb to early-April in the evening sky and September/October in the morning sky -- it's then that the ecliptic, along which the cone of the zodiacal light lies, is steepest in our skies. The
Gegenschein can be seen in the area of the sky opposite the sun. To view either, you must get yourself to a very dark site to cut out the light pollution. When trying to observe either of these phenomena, it is best to do so when the moon is below the horizon. If you are observing them when the moon has risen, restrict your efforts to the period 4 days either side of the new moon as otherwise the moonlight will be sufficient to drown them out.
Finally check out
www.heavens-above.com
for the latest passes of the International Space Station and satellites, details of Space Shuttle launches and passes and for details of Iridium Flare activity.
Clear Skies and hope to see many of you at Whirlpool
Neill McKeown
