Stargazing: So what is a Supermoon anyway

As I have said before in these articles, I do not wholly agree with the term “Supermoon” as it seems to have different meanings to different people and is used indiscriminately.
Now it seems that August’s two Full Moons, which will both be seen low in the sky, have also been dubbed “Supermoons” because of a quirk of the Moon’s orbit around the Earth, which means that the “Full” disc of the moon will be seen on two nights, on each occasion, even though for one of these Full Moons the actual moment of “Full-ness” occurs whilst the Moon itself is still below the horizon.
Full Moon is a moment of time in the continual motion of the Moon in its orbit around the Earth. The moments before and after are, therefore, not Full Moon, although we are unable to perceive any difference visually. The apparent size of the Moon will be exacerbated by its low altitude. When seen with familiar objects (trees, houses) in the foreground, an optical illusion is created making us think that the Moon looks bigger. Apparently, if you view the Moon whilst standing on your head, the illusion disappears.
An easier way to judge the size of the Full Moon (although you would have to repeat the experiment at successive Full Moons) is to take a single frozen pea and hold it between finger and thumb at arm’s length, so that the pea lines up with the Moon. The pea will completely cover the lunar disc, no matter where it is in the sky, high or low altitude, and even when it is a so-called supermoon.
When a second Full Moon occurs within a month, due to the fact that our calendar months are of varying length whilst the Lunar month (Moonth in Anglo-Saxon)) is always approximately the same length, the second Full Moon is termed a Blue Moon.
To confuse matters even further, the Full Moon in August, because it rises Full and is visible all night long, is also called the Harvest Moon, when farmers use the additional light it gave to continue bringing in the crops.
So, this month we are in the position of experiencing two perigee (closest point in the Moon’s orbit to the Earth in this orbit, but not necessarily the closest it can possibly be) Full, Supermoons, the second of which is also a Blue Moon and Harvest Moon.
by John Stapleton
The Star Chart
The sky will look like the chart on August 7 at 9pm and again on August 23 at 8pm. And four minutes earlier on each successive night e.g. 8.56 on August 8.
To use the chart hold it above your head whilst facing South, so that you can look directly from the chart to the sky.
Skynotes
Please note all times given in this article are in GMT, so remember to add an hour to get the time in BST.
Sun: Astronomical darkness increases to six hours by the end of the month, so fainter objects are again becoming observable.
Mercury and Venus: Mercury is poorly placed for observation this month. Venus, however, is an unmistakable object seen in the Western evening sky just after sunset. Venus is at about its brightest at this time. Because Venus is nearer the Sun than the Earth, we see it showing phases which mimic those we see of the Moon at the same time. If you can hold a good pair of binoculars steady enough, you should be able to see this phase. Venus reaches Inferior Conjunction (lies exactly between the Earth and the Sun) on August 13. Great care should be taken when observing both Mercury and Venus as you should NEVER LOOK DIRECTLY AT THE SUN.
Mars: The red planet is in the evening sky but has receded so far from the Earth that it is now barely visible.
Jupiter: The largest planet rises in the Eastern morning sky. The coloured bands and zones on the surface of the planet can be distinguished with small telescopes, as can the Great Red Spot, a colossal hurricane, greater in diameter than the planet Earth. The Galilean moons can be seen with a good pair of binoculars or a small (bird-spotting) telescope.
Saturn: The ringed planet can be found in the evening sky rising just before midnight and remaining visible right through to dawn. The Moon will be close to Saturn on the night of 2nd/3rd and again on August 30, acting as a guide to find the ringed planet. Saturn reaches opposition on August 27, when it will lie due South. The rings get brighter leading up to opposition and fade slightly afterward. This is due to our perspective view of where the shadow of the planet falls onto the rings, thus dimming them from our point of view. Saturn’s largest moon, Titan, can usually be seen with a good pair of binoculars or a small telescope.
Uranus and Neptune: Uranus is visible in the morning sky and it lies close to Jupiter. Look for a tiny greenish disc compared to the pinpoints, which are the stars. Neptune is also a morning planet seen a little south-east of the asterism of the “Circlet” in the constellation of Pisces. In a reasonably sized telescope, Neptune displays a smaller and truly blue disc compared to that of Uranus.
Meteor Shower: The Perseid meteor shower peaks on 12th-13th this month. This is the best shower of the year, with up to 60 meteors an hour, including some very bright ones. This shower is often the brightest and most spectacular, of the annual meteor showers.
This year, the Moon phase is favourable, so many more of the shooting stars should be visible. The Perseids are so called because they appear to radiate from a point in the constellation of Perseus. The maximum of activity takes place on the night of 12th/13th when up to 60 meteors an hour may be seen in ideal conditions.
This figure is standardized by assuming the radiant point will be directly overhead so that meteors travelling in all directions can be seen. However, in actuality, the radiant is relatively low in the north-eastern sky until the early hours, and this is the best time for observation, although it is worth looking out from the moment it gets dark, after 22.30.
Observing meteors could not be simpler. The only necessary bit of equipment is a garden recliner or deck chair, so that you can lay back and look at the sky about 40 degrees above the horizon comfortably. If you want to make a record, simply count the number of meteors you see. You can also note the direction of travel, the duration, which will typically be seconds, and anything unusual, such as colour, faint trails, or sound. This shower is known for producing occasional, bright fireballs.
Comet: There are no bright comets expected this month.
The Full Moon occurred on August 1 with Third Quarter on August 8. New Moon then follows on 16tt with First Quarter on August 24. A second Full Moon then also falls in August on 31. This is what is referred to as a Blue Moon because, whilst not rare, this happens infrequently. Hence “Once in a Blue Moon”. (See main article)