Sky notes are compiled by Dundee Astronomical Society's Director of Observations Jim Barber
Sky Map for 15th August 22:00
Mercury should be at its best appearance in the morning this month.
Venus Reaching greatest eastern elongation on the 17th. Losing altitude just before sunset.
Mars An evening planet, bright and large through a telescope. Rising at approximately 20:00 on the 15th.
Jupiter Starting to disappear from our night sky at the end of the month.
Saturn Moving into an advantageous position for us this month although low in the sky. Just above and to the east of M8 and M20 at the end of the
Uranus Getting close to its highest altitude by the end of the month.
Neptune At its highest point due south at night from mid-August.
Dundee Astronomical Society
Third Quarter 4th August
New Moon 11th August
First Quarter 18th August
Full Moon 26th August
On Saturday 18th there is an opportunity to view Lunar X. The X will appear about 1/3rd up the terminator from its southern edge. Not to make it too easy, the Lunar X appears in daylight at 17:30 UT.
Director of Observations
Dundee Astronomical Society
Here we are into the darker nights (leaving twilight behind) and the night skies becoming longer. We can start thinking about planning what we want to look at over the winter period.
On the 11th of the month from 08:25 UT until 09:20 UT a small Solar Eclipse will be visible. However, there is a catch as unfortunately it will only be visible from the very north of Scotland, with the best views possibly in the northern islands, so for you travellers here is an opportunity to see this. Again, and I do not apologise for this, if you intend to view an eclipse or the Sun in general, always use appropriate solar protection with telescopes, binoculars and even with the mark 1 eyeball. You only have one set of eyes so take care of them.
Is there anything of interest out there this month? Well of course there is. In previous months we have spoken about the Summer Triangle, Leo etc, so let’s think about some circumpolar objects we can view. Firstly, there is Cassiopeia ‘The Vain Queen’ with its attendant Andromeda Galaxy (M31), well worth the viewing. Also, there is the Heart and Soul Nebula (IC1805) very close to Segin in Cassiopeia. There are many other objects in and around this constellation, have a look and image if possible. Have a look in our web site and check out Alan Clitheroe’s images.
Other sights in our night sky to track down are, Pegasus the Winged Horse attached to Andromeda with the shared star Alpheratz and of course, there is Andromeda with M31, M32 and M101 to look for. All great evening constellations with interesting objects close by to image. Let’s hope this sunny clear spell continues into August.
Ken's August Moon
Not the best time of the year to view the Moon as the waxing Moon soon loses elevation and first quarter, always a favourite, is only at around 20º at transit. The sad news is that if you want the best views of the Moon during late summer and autumn it’s an early start to the day! Around last quarter the Moon is a much healthier 45º elevation at a transit time of about 07.30 UT. It is still daylight at this time and it would be better to have a look at, or just before, sunrise.
For August I have chosen the 6th when the Moon at 24.5 days old. This will be seen at around 5am a bit south of east and at a reasonable elevation. Again, I have shown the Moon as seen using a refractor or Newtonian reflector without diagonal with south at the top and east to the left. One of the areas which always draws my eye is Mare Humorum. Mare Humorum is notable because it is relatively circular, although appearing as an ellipse due to the curvature of the Moon. It is a lava plain but has many features of interest including wrinkle ridges, rilles and flooded craters. The crater Gassendi, at 88km, dominates the northern end of the mare and is a complex object in its own right. The centre of Gassendi has an impressive group of mountains which reach 1200m. However, it is the floor which requires careful study as it is irregular and has a network of rilles. Gassendi A is a smaller crater which breaks into the north wall of Gassendi and gives it what some observers call a ‘diamond ring’ effect.
Opposite Gassendi on the southern side of Mare Humorum is the eroded and partly lava flooded crater Doppelmayer. The south-west wall is relatively intact but the south-east dips into the mare. I visualise the impact which formed the crater hitting the south side of the Humorum basin so that the crater was on something of a slope. The subsequent infilling of Mare Humorum with lava also flowed into Doppelmayer but it can’t be all that deep as the central peak remains protruding above the basalt. I must admit that I find these semi-submerged craters particularly fascinating as they are found along the inner edges of several maria and each show different degrees of engulfment.
Towards the west of Mare Humorum is one of several linear or arcuate features, some which follow the general curvature of the mare. This feature, Rupes Liebig, is the most prominent of these and is a fault which extends about 180 km from the north edge of the crater Liebig. This should easily be seen in a small telescope, but it is worth looking around the area, especially with a bigger instrument, as there are a number of rilles nearby.
Moving to the south-east side of Mare Humorum and outside the actual mare basin you should see at this illumination the three distinct arcuate lines of the Rimae Hippalus. These follow the shape of the mare basin and are often referred to as rilles, but I suspect they are graben faults which have been produced by the pull exerted on the area round Mare Humorum as it filled with basalt. The faults are named after the flooded crater Hippalus through which one of them passes. This is another partly lava flooded crater which is worth a look to see how the fault almost bisects the crater.
A bit away to the south-west is the impressive walled plain of Schickard. At 227 km in diameter is does stand out and it is worth looking at the variation in colour of the basalt within the walls. The light and dark areas are reminiscent of the basalts of many of the maria, and indeed there is no reason to suspect that these basalts are any different, showing differentiation and probably layering with time. There are a number of small craters within the plane, particularly towards the south-west where there is a hint of parallel ‘abrasions’ which are neither rilles, crater chains nor faults but look very like some other areas of the Moon which have been scoured during the formation of nearby large craters or maria.
Persieds are one of the most plentiful showers (50-100 meteors seen per hour) and occurs with warm summer night-time weather, allowing sky watchers to easily view them. Perseids are also known for their fireballs. Fireballs are larger explosions of light and colour that can persist longer than an average meteor streak. This is because fireballs originate from larger particles of cometary material. Fireballs are also brighter. The peak of the meteor shower occurs on the evening of the 12th and morning of the 13th. With a new moon on the 11th and the skies being clear we should see a spectacular show. Find a nice dark area to view from and enjoy.
Graphic courtesy of Sky at Night Magazine
Graphic courtesy of Sky at Night Magazine
Comet 21P/Giacobini-Zinner passes above Cassiopeia and below Camelopardalis mid to end August. With a Magnitude reaching +7.2 on the 21st, it is well worth looking out for. Should be visible with binoculars and a small telescope.
So far, the NLC count has been extremely encouraging, with Ken and Pam reporting their best haul so far. Tony has reported his first ever sighting and myself and Bill have also captured a few images. Unfortunately, certainly down here in Fife we have had hot warm days but overcast nights, so nothing seen lately.
As usual, keep a look out and if you capture any images please let Ken know (giving location, date and time - if local or UT) and if possible a rough elevation.
Jim's Focus of the Month
Cassiopeia is visible all year in the Northern hemisphere. With its simple 'W' shape and the brightness of its stars it makes Cassiopeia one of the most easily recognisable constellations in the night sky. There are several interesting deep sky objects in the constellation such as:
NGC 457, also known as the Owl cluster, discovered by William Herschel in 1787. It is also known as the ET Cluster.
M52 is another open cluster which can be viewed with binoculars situated slightly west of Ruchbah. A nice cluster easy to view as you dont need sophisticated equipment
M103 is yet another open cluster and is positioned approximately 1 deg east of Ruchbah with a magnitude of 2.66. It has been described as a sparkling open cluster which can be seen as a fuzzy patch through binoculars.
Remember the Milky Way passes through Cassiopeia so have a look and tell us what you see.
Did You Know?
5th August 2011 Juno launched to Jupiter to understand its origin and evolution.
10th August 1966 Lunar Orbiter 1 launched. After entering the Moons orbit, it takes the first images of Earth from that vantage point.
17th August 1933 the world's first hybrid liquid-propellant rocket launched by the USSR.
18th August 1985 Japanese spacecraft Suisei launched for encounter with Comet Halley.
24th August 2006 Pluto officially classed as a Dwarf Planet by the IAU.
27th August 1962 Mariner 2 launched on a flyby trip to Venus.