By Duncan Lunan   

The Moon will be Full on August 3^rd, and again on August 31^st, a ‘Blue Moon’ Full twice in the same month, and both of them ‘Supermoons’ when it is at its closest to Earth as well as Full.  The Third Quarter Moon, half full and waning, will be near Jupiter on the 8^th.  It will be New on August 16^th, and its thin crescent will be near Mars and Mercury on the early evening of the 18^th, all very low in the twilight.

The definition of a ‘Blue Moon’ as two Full Moons in one month is comparatively modern;  the phrase used to refer to the third of four Full Moons in a quarter, but in 1946 was mistakenly defined as the second of two Full Moons in a month, and now seems to be used for both of them.  Actual blue moons are proverbially rare and are caused by volcanic dust, smoke or smog.  In 1950 there were very large forest fires in Canada for five months, which blacked out parts of the US eastern seaboard.  That September, a smog of oil droplets from them crossed the North Atlantic, and caused blue Suns and Moons as it crossed Greenland, Iceland, northern Europe and Scotland.  I remember it vividly because my grandmother took me to Troon beach to see the blue Sun, and the whole familiar landscape was alien, under a bronze sky.  I was really annoyed that my parent wouldn’t allow me to stay up for the blue Moon, because I had school next day.  But when we’re being told that such events ‘must’ be due to global warming, it’s worth remembering that they sometimes happened more than 70 years ago.

Just when I thought I was up to date with lunar probes, India’s Chandrayaan-3 spacecraft lifted off on 14^th July, with little preliminary fanfare.  Chandrayaan-1 was a successful lunar orbiter in 2008, which confirmed both the presence of water ice at the lunar poles, and the thin atmosphere of water vapour, generated by interaction of the Solar Wind with rocks on the daylit face of the Moon.  Chandrayaan-2 attempted to land near the lunar south pole in July 2019, but lost contact when only 2.1 km above the surface.  Chandrayaan-3 is making 5 orbits of the Earth, working outwards, then it transfers to the Moon’s sphere of influence and loses height over 5 descending orbits, before attempting descent from a height of 100 km over the south pole on August 23^rd or 24^th.  As of July 20^th, the first four orbit-raising burns had been completed  (Fig. 1), with the last scheduled for July 25^th and the translunar insertion scheduled for July 31^st.  But India may be pipped at the post for the honour of being the fourth nation to land a spacecraft on the Moon.  After years of delay, with a launch originally scheduled for 2016, Russia has announced that Luna 25, its first moonprobe since Luna 24 in 1976, will be launched on August 11^th.  It will be the first moonprobe of their own because the first 24 were Soviet, as they insisted at the time.  The announcement comes despite the withdrawal of international cooperation following the invasion of Ukraine, and that includes a precision guidance system for landing which had been developed by the European Space Agency.  Whether Luna 25 will get to the Moon first, and whether it will land successfully, remain to be seen.

The planet Mercury is generally too low to be visible, even though it’s at maximum elongation from the Sun on August 10^th.  With binocular aid, it might just be found below the young crescent Moon on the 18^th, but the odds are against it.  Make sure the Sun has gone down before hunting for the planet.  

Venus is at inferior conjunction with the Sun on 13^th August  (caution – don’t look for it!)  and reappears in the morning sky in the last week of the month, rising about 5 a.m., and bright from the outset.  

Mars is effectively out of sight behind the Sun.  Like Mercury, it might be found with binoculars to the left of the young crescent Moon on the 18^th, after sunset, but it’s not likely in this latitude.  

The Ingenuity helicopter has been out of touch with the Perseverance rover since April 26^th, having landed by chance where communication was cut off by a ridge of rock.  Contact was resumed on June 28^th, allowing the helicopter to download data and images from its 52^nd flight, and after that it’s been business as usual.  Meanwhile results continue to be published from China’s Zhurong rover, which has still not renewed contact since the last Martian winter.  It seems that there was a 70 degree shift in the deposition pattern of sand dunes at the landing site, about 400,000 years ago, and this may have been due to a shift in Mars’s axis due to what’s called the Milankovitch Cycle of perturbations – which is much less for Earth, due to the stabilising influence of the Moon.

Jupiter rises about 11.00 p.m. in Aries, passed by the waning Moon on the mornings of 8^th and 9^th August, when the Moon is between Jupiter and the Pleiades.  The shadow of the volcanic moon Io will cross the planet’s disc on the mornings of August 14^th and 30^th, while the largest moon in the Solar System, Ganymede, will cross the disc along with the Great Red Spot on the morning of the 17^th.   

Saturn in central Aquarius can be seen all night, and it comes to opposition, due south at midnight (GMT/UT)  and at its closest to us, on August 27^th.  The rings will be at their brightest then, reflecting sunlight back towards us.  Before that, the Moon is near Saturn on 2^nd and 3^rd August, and afterwards the Blue Supermoon passes below it on the night of the 30^th/31^st.    

Uranus in Aries rises at 11.00 p.m., about the same time as Jupiter, and is near the Moon on August 9^th.  On the 29^th August Uranus comes to its ‘stationary point’ and appears to reverse its motion in the sky as it begins to be overtaken by the Earth, before opposition in November.

Neptune is in the sky all night, in Pisces, with opposition to come in September.  Neptune is near the Moon on August 4^th.  

The Perseid meteor shower is expected to peak on the night of August 12^th/13^th.  The Moon won’t spoil things because it will be a thin crescent, rising not long before dawn.  Although this is one of the most regular meteor showers of the year, and I saw a fantastic display from Turkey in 2005, it can be disappointing.  The meteors come from Comet Swift-Tuttle, the Great Comet of 1862, which has an orbital period of 133 years and last came past the Sun in 1992, so although it’s not as far away as it can get, it’s a long way out, travelling more slowly, and the meteors here will be correspondingly fewer.  Nigel Henbest’s Stargazing 2023 calls the event ‘guaranteed celestial fireworks’, but there have been years when I’ve seen nothing, and the central part of the stream won’t enter the atmosphere until morning over the USA, so that guarantee is a bit shaky.  The meteors will appear to come from a point on the Milky Way called the radiant, near the Double Cluster in Perseus  (Fig. 2), but to see them it’s best to look around that over the rest of the sky.

Duncan Lunan’s recent books are available through Amazon.  For more information see Duncan’s website, www.duncanlunan.com.