Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Telescope House September 2022 sky guide
September brings the Autumnal Equinox for the Northern Hemisphere and the Vernal, or Spring Equinox for this in the Southern Hemisphere. This year these events occur on 23rd of September, where for a brief period for day and night are of nearly equal length. The etymology of the word “Equinox” comes from the Latin “Equi” - equal and “Nox” - night. This equality of dark and light really depends on where you find yourself, as there are few places on Earth on the 23rd September where day and night are truly equal. However, crucially, the 23rd marks the point where the Sun crosses into the southern celestial hemisphere - which results in increasingly more hours of darkness than light for those of us in the Northern Hemisphere and of course increasingly less darkness for those in the Southern reaches of our planet. Many people for whom astronomy is of no more than at most a passing interest will bemoan the lack of daylight in the Northern Hemisphere - the same cannot (in all probability) be said of the many readers of this Sky Guide. For us astronomers in higher northern latitudes, the dive towards Winter does have its perks.
As ever, there's a lot to see in skies above us this month...
The Solar System
The Moon begins its monthly amble around the sky in the constellation of Libra. At 29% illuminated waxing crescent phase, the Moon rise little afternoon and transit around 5 pm, setting a just before 10 pm on the 1st.
At this time of the year the Moons new crescent phase occurs what is it is in the most southerly part of the Ecliptic. Subsequently, the Moon won’t appear to rise particularly high above the horizon, especially for those in higher northern latitudes.
The Moon comes to First Quarter phase on September 3rd, when it will be briefly resident of the constellation of Scorpius, sitting just above the prominent red star Antares, the heart of the scorpion, in the early evening. The Moon continues it swoop through the lowest part of the Ecliptic over the next few days passing through Ophiuchus, Sagittarius and only into Capricornus and then Aquarius, where it becomes Full on the evening of September 10th. On this evening, the Moon will rise at a little past 8 pm and transit at just before 1 am the following morning, setting at just after 6 am. Naturally, this part of the month will be an inopportune time for observing for deep sky targets, or imaging these with anything other than very severe filtration.
The Moon continues to climb up the northerly part of the Ecliptic through Pisces, Cetus, and then back into Pisces. On the evening of the 12th the Moon appears a little to the east of Jupiter, the two will making a prominent pair in the sky.
On the evening of the 14th, the Moon, now in the constellation of Aries, will occult the planet Uranus. This event will be a relatively short one, taking place just after Moonrise from Western Europe. The occultation will begin at a little after 10:25 pm (BST) and Uranus will emerge from behind the Moon at around 11:17 pm (again, BST). Occultations of Uranus are difficult to observe, due to the inherent faintness of the planet in comparison to the Moon’s overarching brightness, but if you have reasonable size binoculars or a telescope, it may be interesting to see if you can detect it.
The Moon occults Uranus, 10.27pm (BST) 14th September 2022. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
The next few days find the Moon drawing closer to the most northerly point in the Ecliptic, passing through the constellation of Taurus from the 15th to the 18th. On the evening of the 16th, a day before the Moon reaches Last Quarter, it will be found just to the north of the increasingly prominent Mars, in Taurus. This again should be a pretty spectacular sight for widefield observation, but you will have to be an early riser to see it at its best - the Moon and Mars transit at around 6:30 am (BST) on the morning of the 17th.
The next week or so find the Moon cresting over the top of the northern part of the Ecliptic and down its southerly side. This part of the year affords morning observers the chance to see the Moon in late waning crescent phase at a particularly high separation from the horizon. Similarly to Spring’s “High Evening Crescent” phases, we are now entering into the period of the Moon’s “High Morning Crescent” phases, as observed from the northern hemisphere. As the Moon moves through Gemini and Cancer over the next few days, we can observe its Waning illuminated phase in very sharp relief, at a significant elevation from the horizon. The combination of improved seeing conditions, due to the Moon’s elevation and the dramatic illumination of the steadily decreasing crescent, will reward the early riser. This is arguably the best time of the year for northern hemisphere astronomers to observe our natural satellite’s western limb.
The Moon, steadily diminishing in phase, will begin to dip down towards the Sun towards the latter part of the month, decreasing its apparent separation from our parent star, as it draws between the Earth and the Sun. On the morning of the 25th, the Moon will sit a little to the east of Venus as the Sun rises, though it will be illuminated by just 0.5% and to all intents and purposes be unobservable. New Moon technically occurs a little later in the day, as it draws closest to the Sun.
After New Moon occurs, the Moon will remerge on the evening side of the Sun, though will again sit fairly low to the horizon during its Waxing Evening Crescent phase. Moving through Virgo, into Libra and back into Scorpius, the month ends with the Moon again sitting very close to Alpha Scorpii, Antares, as the Sun sets on the 30th.
Sitting in Virgo, to the east of the Sun in the evening sky, Mercury is a steady, if rather unspectacular +0.4 magnitude, presenting a 7.9 arc second, 45% illuminated disc, on the evening of the 1st. As the planet is sitting in a rather shallowly-setting part of the sky, it will not appear very high above the horizon at all for those in higher northern latitudes. From 51° north, Mercury appears to sit just three and three-quarter degrees above the horizon at sunset. This means it will be very difficult to observe, even for those with clear westerly horizons. Mercury is also sinking in a southerly direction, towards the Sun - and this will compound the difficulty of observation as the next few days continue. Those in more southerly parts of the world, particularly around the equator, will be able to observe Mercury with much more ease.
By mid-month, Mercury will have sunk below the Sun from mid-northern latitude and will be impossible to observe from these areas.
Mercury’s Inferior Conjunction will take place on the 23rd of September, when it will be found in between the Earth and the Sun. It will then re-emerge as a morning target, but will take some time to gain reasonable elevation and become observable. However, by the end of the month Mercury is in a better position for observation in the morning sky, sitting at an elevation of over 8° (as observed from 51° north), displaying a magnitude of +1.7. Mercury will continue to improve in both brightness and elevation above the horizon into the early part of October, which will represent one of the best morning apparitions of the planet this year.
Mercury and Venus, sunrise, 30th September 2022. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Venus is most definitely a morning target at this time. We begin the month with the planet situated in the constellation of Leo, separated from the Sun bye just under 14°. At -3.9 magnitude, Venus will – as ever - be extremely easy to observe, as long as you have a clear easterly horizon. The morning of the 1st finds the planet standing at a little over 11 1/2° elevation (from 51° north), at sunrise.
Venus is steadily drawing towards the Sun and Superior Conjunction, which it will reach in late October. As the month progresses, not much changes in terms of Venus‘s brightness, but its separation from the Sun diminishes considerably. By the 15th, Venus will stand just over 8 1/2° above the horizon at sunrise. By the time we reach the end of the month, on the morning of the 30th, Venus will be separated from our parent star by just over 6° - and will sit just over 5° elevation at sunrise (again, from 51° north). The trend is definitely decline, as far as Venus is concerned, so catch the planet as early in the month as you can.
Where Venus is in decline, Mars is exactly the opposite. We are now at the beginning of September - a little over three months from Martian opposition at the beginning of December 2022. The 1st find Mars sitting in between the Pleiades and Hyades star clusters in Taurus, at -0.1 magnitude, displaying a disc which is illuminated by 85% and just under 10 arc seconds diameter. As suggested in last month’s sky guide, it will be interesting to compare Mars with the nearby Aldebaran, Alpha Tauri, as the two are quite similar in colour and also very similar in brightness at this point in time.
Mars in Taurus, in between the Hyades and Pleiades star clusters, 1st September 2022. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Turning your telescope towards Mars at this time will start to become quite a rewarding experience. Although Mars is still relatively small in size, it should be possible to observe darker continental-sized features and the south pole of the planet, if conditions are kind. Coloured filters can also be used to isolate certain features.
By the middle of the month, Mars has tracked a little further east in the Ecliptic and more now sits to the east of the Hyades star cluster. By this point it has brightened to -0.3 magnitude and now displays a disc just under 11 arc seconds diameter.
By the end of the month, Mars will have brightened yet further to -0.6 magnitude and on the evening of the 30th, will display a disc just under 12 seconds in diameter, illuminated by 87.5%. Although the Red Planet has still some way to go before reaching its best and is also most definitely a better early morning target, those who are prepared to rise early enough will start to be rewarded by quite an impressive sight in larger telescopes, by September’s end.
The King of the Planets, Jupiter, reaches its brightest and closest point to Earth - and comes to Opposition on September 26th.
We find Jupiter in the non-zodiacal constellation of Cetus on the evening of the 1st, shining at a brilliant -2.9 magnitude, displaying a 48.7 arc second diameter disc.
By mid month, Jupiter will be the same brightness, though has tracked back in a retrograde direction in the Ecliptic, into the constellation of Pisces and is now displaying a 49.64 arc second diameter disc.
Opposition night finds Jupiter at fractionally below -2.93 magnitude, displaying a 49.9 arc diameter disk - this is not far below the maximum possible 50.1 arc seconds diameter it can reach from our perspective here on Earth. Indeed, this Opposition of Jupiter will be the largest apparent diameter (and brightness) that the planet reaches this decade. It won’t be this big or as brilliant until 2034 - though next year’s showing will be nearly as big as this year’s. Jupiter can never quite hit the -3.0 magnitude range, as observed from our planet. It can peak at -2.94 magnitude - so we’re not too far off maximum here. We also have the added bonus of Jupiter sitting significantly higher in the sky than it has in recent years, as seen from a northern hemisphere perspective, with the considerable improvement in seeing conditions that this brings. All-in-all, this Opposition promises much - as long as the weather delivers.
The planet will rise at just after 7 pm (BST) on Opposition night and transit add a little after 1 am the following morning, setting at a little after 7 am.
Jupiter, with great Red Spot transit, 11.30pm, Opposition evening, 26th September. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
There are a few mutual transit events to look forward to for those with telescopes to observe. At around midnight on September 3rd, there’s a nice mutual transit of the Great Red Spot and Io. At just after midnight on September 10th there’s another GRS/Io/Io shadow transit to observe. At just after 9 pm on September 17th there’s a favourable GRS/Europa transit. This is followed by a similar event starting at around 10 pm on September 24th.
Jupiter ends September still a resident of Pisces and still shining at -2.9 magnitude. The planet now displays 49.8 arc second diameter disk.
Saturn is just past Opposition itself, which occurred on the 14th of August. As such, it is still very favourably situated for observation, rising just before 7:30 pm (BST) and transiting at a little after midnight on the 1st. The Ringed Planet shows a visual magnitude of +0.3 and apparent size of 18.7 arc seconds diameter at the month’s beginning.
As September progresses, not a huge amount changes as far as Saturn is concerned. The evening of the 15th finds the planets +0.4 magnitude and now displaying an 18.5 second diameter disc. It will rise at a little before 6:30 pm and transits just after 11 pm.
Saturn and major moons, early evening, 15th September. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
By the end of the month September, Saturn will have dimmed fractionally 2+0.5 magnitude but still displays a healthy 18.1 arc second diameter disc. At this point, it will rise at a little before 5:30 (BST) and transit at just after 10 pm. Reaching an altitude of around 23° at its highest point, from 51° north, Saturn is still not ideally placed for those in higher northern latitudes to observe telescopically. But it is such a lovely target that even if seeing conditions are not great, it’s still very rewarding to observe. As Saturn never reaches the dizzy heights of Venus, Jupiter and Mars at their brightest, it is argued by some observers that less-than-ideal seeing conditions affect the observation of Saturn more kindly than they do brighter targets. While this is probably down to visual perception of atmospherically-induced errors being somewhat more difficult for fainter targets, than they are for brighter ones, it’s well worth testing your personal perception of this on Saturn, if you have your own telescope to observe with.
Uranus and Neptune
As previously reported, probably the highlight of observational opportunities as far as the outer gas giants go this month is the Moons occultation of Uranus. However, it is not only Jupiter that comes to Opposition this month, but also Neptune which reaches closest point to Earth on the evening of 16th September.
Neptune is not far from Jupiter in the sky, sitting as it does on the border between Aquarius and Pisces. As September progresses, Jupiter begins to draw closer to Neptune, providing a useful pointer for the rough location of the outer planet in the sky.
Unlike the brighter Uranus, Neptune can never be seen by the naked eye, reaching +7.8 magnitude on the evening of opposition. The planet displays a 2.4 arc second diameter disc, which is within reach of binoculars and smaller telescopes, if your observing area is fairly free from light pollution.
As seen in a telescope at fairly decent magnification, Neptune appears a vibrant blue in colour, which is generally remarked to be more prominent than Uranus‘s green-grey hue. In truth, while Opposition is the best time to observe any of the outer planets, in the case of Uranus and definitely Neptune, they are so far removed from our position here in the warmth of the inner solar system, that brightness and apparent size vary very little in regards to wherever they are observed on our orbit around the Sun. Even at its furthest observable position from Earth, Neptune only appears 0.2 magnitudes fainter than it does at the height of Opposition. Still, around this time presents the best observational opportunities for study of the solar system’s outmost “true” planet.
Neptune will rise at just before 7:30 pm, transiting a little before 1:15 am (BST) on Opposition night.
Uranus is further east in the Ecliptic, in the constellation of Aries. At +5.7 magnitude, displaying a 3.7 arc second diameter disc, technically it is in the reach of naked eye observation under ideal conditions. However, in practice, binoculars are very often needed in order to make positive identification of the planet at all.
Rising at a little after 9 pm and transiting at just after 4:30 am the following morning, during mid-Month, Uranus is most definitely better-seen in the early morning sky. It will come to Opposition in November 2022.
Uranus and Neptune's relative positions, mid-September 2022. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Comet C/2017 K2 (panSTARRS) has put on a very reasonable display in the early evening sky over the past couple of months. The beginning of September find the comet in the head of Scorpius and while it will be technically possible to observe it a little after sunset, in truth, those of us in the northern hemisphere are, close to losing the opportunity to observe it at all. The comet is heading in a very southerly direction and this will make observation impossible beyond the very beginning of September, for those in higher northern latitudes. Those in the southern hemisphere, however, will be able to observe the comet for a much longer period of time - into 2023. It is expected to stay around the 8th magnitude for some time, which will make it a relatively easy target in small telescopes or larger binoculars.
Comet C/2017 K2 (panSTARRS) path through September (comet position shown 1st Septemeber). Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
It has been reported from a couple of sources that the relatively recently-discovered comet C/2022 E3 (ZTF) shows signs of potentially becoming reasonably bright. It could become as bright as magnitude +4 in late January/early February of next year. However, as we have often pointed out potential is one thing - actuality is another, certainly as far as comets are concerned. At time of writing, the comet is a resident of Hercules, at around 13th magnitude. Come the end of January and beginning of February, C/2022 E3 (ZTF) will be circumpolar in the northern hemisphere and rocketing through the polar regions at quite a speed - an impressive 6° plus a day when during closest approach to Earth. It will pass us at a respectable 0.28 AU at nearest. Certainly one to look out for, though as ever, there’s no guarantees of a decent display.
There are no major meteor showers during September. Observers out in reasonable locations in the early part of the month, may see the absolute tail end of the Perseid meteor shower, which can last until the early part of August/beginning of September. However, when you are out of particularly dark location, there is always a good chance of seeing a sporadic meteor, which can come from any direction in the sky and not be associated with any particular shower.