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Post date: Sep 30, 2020 11:42:12 AM
by Anne Holt
Sunrise 1st: 07.11 31st: 07.06
Sunset 1st: 18.44 31st: 16.37
Astronomical darkness 1st: 20.41 to 05.15 31st: 18.36 to 05.09
BST ends on Sunday 25th at 02.00
Full Moon: 1st at 22.05
31st at 14.49
New Moon: 16th at 20.31
Lunar apogee: 3rd at 17.24 (406319 km)
31st at 18.47 (406392 km)
Lunar perigee 16th at 23.48 (356912 km)
The Full Moon on 1st is the Harvest Moon as it's the one closest to the Autumn Equinox, which was on Sept 22nd. Other names are the Hunters' Moon, the Dying Grass Moon, the Chinese Kindly Moon and the English Medieval and Neo Pagan Blood Moon. To the Celts and the North American Cherokee it was also the Harvest Moon, it was the Choctaw Blackberry Moon and the Algonquin Raven Moon. The Dakota Sioux again have the most descriptive name - the Moon when Quilting and Beading are Done.
The New Moon on 16th is only a few hours before perigee, so it is a Super New Moon. Of course, we can't actually see the New Moon but the thin crescent a day or so later will appear larger than average. We have 2 Full Moons this month, some sources say that the second one in a calendar month is a Blue Moon but this is inaccurate. The true definition is the third Full Moon in a season which has 4. The current season, going from the Autumnal Equinox to the Winter Solstice, has only 3, so no Blue Moon. Either way, the Full Moon on 31st will be the same colour as always.
Highlights
As always in October we have plenty of astronomical darkness - eight and a half hours at the start of the month, a couple more by 31st. GMT returns towards the end of October, so we have noon and midnight at the correct time for the next 5 months.
We have 2 Full Moons, the first is the Harvest Moon the second will be called a Blue Moon by some, but isn't really. Both are close to apogee so will appear smaller than average.
Venus is still brilliant in the pre dawn sky and Jupiter, fading but still very bright, is an early evening object.
We have several minor meteor showers and a good chance of a few fireballs, especially towards the end of the month when the Southern and Northern Taurids are both active. The one middling shower, the Orionids, might be much better than average this year. On the other hand, of course, it might not!
The real highlight this month is Mars, at its closest to us on 6th and at opposition on 14th. During this time its magnitude will be -2.6. Because it takes only 687 days to orbit the Sun, it moves away from us quite quickly and it is only so close to us, and therefore so bright, for a short time, by month end it will have started to fade again. Mars has a big variation in magnitude between perigee, when it reaches -2.6 to -2.8, and apogee, when it's down to around 1.6 or 1.7. This is because, as with all the outer planets, the difference in distance, which is 2AU - the diameter of the Earth's orbit - is a greater proportion of the total distance than it is for the much further gas and ice giants. Mars is about 7 times further from us at apogee than it is at perigee. For Jupiter it's only about 1.5 times.
And finally, if you've ever seen the internet urban myth, which often appears around opposition, 'tonight Mars will appear the same size in the sky as the Full Moon', of course it won't. Apparently, at the 2003 opposition someone commented that Mars, when seen through a scope with a magnification of around x75, would appear the same size as the Moon does when seen with the naked eye. Someone, somewhere, missed the bit about the telescope and the myth was born.
Constellations
The Summer Triangle, made up of Vega in Lyra, Deneb in Cygnus and Altair in Aquila, is losing its dominance in the night sky. It is still visible during the first part of October high in the south west but by the end of the month all three constellations will have set by 4am. It's place in the southern sky is being taken by the Great Square of Pegasus, autumn's signature constellation.
The beautiful star cluster the Pleiades (also known as the Seven Sisters) followed by the rest of Taurus, will be visible by 11pm in early October and by 8pm (now back to GMT) at month end.
By the end of October Orion will be easily visible by midnight, with Sirius just above the eastern horizon at this time.
Perseus and Andromeda are still high in the sky for most of the night, making it a good time to look for M31, the Andromeda galaxy. If you are at a very dark sky site, it should be visible to the naked eye, especially when using averted vision.
Cassiopeia is now high in the sky for most of the night, so the Plough, on the opposite side of the North Celestial Pole, is low in the north.
Planets
Mercury: in Virgo, mag 0.0
An evening object in theory but, in practice, almost impossible to see as it is so low in the sky. On 1st it is at Greatest Eastern Elongation, separated from the Sun by almost 26 degrees. However, because of the shallow angle of the ecliptic at this time, it has sunk below the horizon by the time the sky begins to darken, setting only 20 minutes after the Sun. It moves into Libra on 6th and reaches inferior solar conjunction on 25th, now down to mag 5.8 and passing about one degree south of the Sun. By 31st it will have brightened to mag 2.8, rising at 06.09, an hour before the Sun, but still not visible as it appears only 9 degrees from it.
Venus: in Leo, mag - 4.1
Still shining brightly in the morning sky, an unmissable sight for early birds and insomniacs. On 1st it rises at 03.12 and should be high enough to be easily visible about an hour later, reaching 30 degrees in the east by dawn. During the first few days in the month it is very close to Regulus, alpha Leonis, the dot at the bottom of the reverse question mark asterism which represents the head of the lion. It is closest, only a few arcminutes to the SE, on the morning of 3rd. On the 14th the 9% lit Moon passes 4 degrees 2' north of the planet at 03.50, just as it is rising. It moves into Virgo on 23rd and should be visible from 05.15, getting to 26 degrees in the SE in reasonable darkness. It is at perihelion (closest point in its orbit to the Sun) on 30th. Because its orbit is almost circular there is very little variation in the amount of light and heat it receives. On 31st, now at mag -4.0, it rises at 03.36 (GMT) and is at 24 degrees in the east by dawn.
Mars: in Aries, mag -2.5
The star of the show this month. On 1st it rises at 19.25 and should be easily visible an hour later, when it reaches 7 degrees in the east, culminating, 42 degrees in the south, at 02.06. On 3rd the just past full Moon passes to the south of the planet, the pair will be separated by about 3 degrees at midnight on 2nd/3rd, moving closer till about 5am, when they are just 39' apart. As last month, there will be an occultation but once again it isn't visible from the UK, only those at the southern tip of South America or sailing in the S Atlantic will be able to see it. On 6th it is at its closest to us (perigee) when it will be at a distance of 0.41 AU. It will now be at mag -2.6, reaching 42 degrees in the south at 01.40. It is at its brightest around midnight on 12th/13th when its magnitude is -2.62. It is at opposition on 14th, when it rises at 18.22 and gets to 7 degrees in the east an hour later, culminating at 00.59. It won't be quite as close to us, therefore as bright, as it was at the last opposition in July 2018, but makes up for it by being in a much better position - then it was in Capricorn and only got to 8 degrees above the horizon. Fingers crossed for clear skies this time, as this is the best it will be until 2035. On 29th Mars is again visited by the Moon, the planet, now down to mag -2.2, will be 3 degrees to the north at 18.00. On 31st it rises at 16.00 and will be at 8 degrees in the east as the sky darkens. It reaches its highest point, 41 degrees, at 22.30 and sets at 05.03.
Jupiter: in Sagittarius, mag -2.4
Now an early evening object, fading but still bright enough to be easily seen in the darkening sky. On 1st it culminates, 13 degrees in the south, at 19.43 in astro twilight, and should be visible until around 22.00 when it is down to 8 degrees in the SW. On the evening of 22nd, as the sky darkens, the 41% Moon will be just south of the planet. They are closest, 2 degrees, at 18.26, a few minutes before it reaches its highest point. On 31st, now at mag -2.2, it culminates about 20 minutes after sunset and should be visible for a couple of hours from 17.00, setting at 20.48.
Saturn: in Sagittarius, mag 0.5
Slightly higher and much fainter than nearby Jupiter, the pair are moving closer - Saturn is 7.4 degrees to the east on 1st, down to 5.2 degrees on 31st. On 1st it is at its highest point, 14 degrees in the south at 20.14 and should be visible till shortly after 22.00, when it is at 11 degrees in the SW. On the night of 22nd/23rd the 46% Moon moves to the south of the planet after its close encounter with nearby Jupiter, They are separated by about 5 degrees at 20.00, closest, 2 degrees 34', at 05.15 after they have set for Manchester observers. On 31st it should be visible at 15 degrees in the south, by 17.20, ten minutes before reaching its highest point. It will be down to 11 degrees in the SW by 19.15 setting a couple of hours later.
Uranus: in Aries, mag 5.7
High in the sky for most of the night, it's now at its best for the year - in fact the best positioned that it's been for about 50 years. Given a dark sky site it should be easily visible in binoculars and even to the naked eye, if the eye in question has perfect vision. A small scope should show its blue.green disc but a large scope is needed to see any variations in the mainly featureless disc. On 1st it reaches 21 degrees in the east by 22.00 and culminates, 50 degrees in the south, at 02.58. On 4th, the 91% Moon passes just less than 5 degrees 30' to the SW at 05.00. The Moon is again close on the night of 31st - 4 degrees to the south at 19.00, when Uranus is 20 degrees above the eastern horizon. On this night it is at opposition, directly opposite the Sun in the sky, so at its highest point around midnight. It rises at 16.29 and is at 50 degrees in the south at 23.52, down to 21 degrees in the west by 04.45.
Neptune: in Aquarius, mag 7.8
Still quite high in the sky for most of the night, especially in the earlier part of the month. On 1st it is at 22 degrees in the SE at 21.00, its highest point, 31 degrees in the south by 23.46, and down to 21 degrees in the SW by 02.30. On 31st it is 22 degrees in the SE at 18.00, culminating, 8 degrees higher, at 20.45 and down to 22 degrees before midnight, setting at 02.22.
Dwarf Planets
Ceres: in Piscis Austrinus, mag 8.2
The closest and brightest of the dwarf planets is too low to be viewed or imaged this month. On 1st it culminates at 22.54 but only reaches 11 degrees in the south. It moves into Aquarius on 13th and at the end of the month reaches 12 degrees by 19.51, now fainter at mag 8.7.
Pluto: in Sagittarius, mag 15.1
It is in the same area of the sky as Jupiter and Saturn but, as it is so much fainter, is not an easy target for imaging. It doesn't get higher than 13 degrees and sets before midnight in early October, and by 9pm (now GMT) on 31st.
Haumea: in Bootes, mag 17.4
Too low for successful imaging as it heads towards solar conjunction on 20th. On 1st it is 18 degrees above the horizon at dusk, setting at 22.18. On 20th it is on the opposite side of the Sun to the Earth but, because its orbit is highly inclined to the ecliptic (28 degrees), passes 26 degrees above the Sun and is 13 degrees above the horizon at dusk. On 31st it rises at 04.21 and sets at 19.21, still only at 10 degrees as the sky darkens.
Makemake: in Coma Berenices, Mag 17.4
Very low in the sky but its position is improving after last month's solar conjunction. On 1st it rises at 05.15 and sets at 21.58, still an evening object as, like Haumea, it passed above the Sun, but only 13 degrees at dusk. By month end it is a morning object, quite high in the sky (25 degrees) for about half an hour from 05.10.
Eris: in Cetus, mag 18.8
Well placed this month but very faint, a difficult subject for imaging, even for the very best amateurs. On 1st it rises at 20.18 and is high enough from 23.00, culminating, 34 degrees in the south, at 02.15. It is at opposition on 17th, when it reaches 21 degrees in the SE by 22.00 and culminates at 34 degrees at 01.12. On 31st it is higher than 20 degrees from 20.00 to 02,30, reaching its highest point, still 34 degrees, at 23.12
Asteroids
Two reach opposition in October.
11 Parthenope
At opposition on 23rd, in Pisces, mag 9.4, culminates at 01.07, 40 degrees in the south.
471 Papagena
Opposition on 27th, in Cetus, mag 9.5. Reaches 27 degrees in the south at 00.17.
Comets
Nothing noteworthy this month, all the comets around are either very faint, very low in the evening sky - or both.
Newly discovered C/2020 Q1 (Borisov) discovered on August 18th by Gennady Borisov, is in Cepheus, circumpolar at the start of the month and high in the sky for most of the night. However it is only around mag 11, and predicted to fade to 13 by the end of October.
Websites for more information and exact positions of all solar system objects
Meteor Showers
One middling (but might possibly be good) and several very minor ones, this month
Orionids: active Oct 2nd to Nov 7th, peak on the night of 20th/21st, ZHR 20 to 25 from a dark sky site. Figure for Manchester given as 11.
This shower often has short periods of reasonable activity during the couple of days before and after the peak. Numbers have been as high as ZHR 50 to 75 but not in recent years. However, if a suspected 12 year cycle of activity proves to be the case, we might have a good show this year. The peak time is around 7am on the morning of 21st, so the best time to look is in the early hours. These are fast moving meteors, often leaving trails. Parent comet is 1P/Halley. There will be no Moon interference but probably some cloud interference.
Camelopardalids: active 5th to 6th, peak in the early hours of 6th, ZHR 5. The radiant, in Draco, is highest at 11am. This very short lived shower has been known to also produce short outbursts and there could be one on the evening of 5th.
Draconids: active 6th to 10th, peak 8th, ZHR 10
Usually seen soon after dusk when the radiant is high in the sky. However a couple of very short outbursts are predicted for the morning of 7th, at 02.25 and 02.57. These are very faint, slow moving meteors likely to be affected by bright moonlight on the morning of 7th and later part of the evening of 8th. Parent comet 21P/Giacobini-Zinner.
Southern Taurids: active 10th Sept to 20th November, peak Oct 10th, with enhanced activity on the days either side of this date. ZHR 5.
These are bright, slow moving meteors so are excellent photographic targets. The radiant is highest at 2am, peak activity predicted for 4am. This shower, along with the related Northern Taurids which are active from the 20th, is often rich in fireballs because the dust cloud left by parent comet 2P/Encke contains many larger than average dust particles.
Delta Aurigids: active 10th to 18th, peak 11th, ZHR 2
The radiant of these is circumpolar, highest around 05.00 so best seen between 2am and dawn.
Epsilon Geminids: active 14th to 27th, peak 18th, ZHR 3
According to the IMO the peak of these could be 4 or 5 days later than the date given. The shower is best seen just before dawn, but on which day is anyone's guess.
Leonis Minorids: active 19th to 27th, peak 24th, ZHR 2
The peak is expected around 07.00 on 24th, so the best chance of seeing anything is just before dawn on that day. The Moon sets at 22.47 on 23rd, so no interference. Parent comet C/1739 K1
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