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December 15 Observing Guide
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9 years 3 weeks ago #105149
by Neill
December 15 Observing Guide was created by Neill
OBSERVING GUIDE
(Please note all times are UT and are based on an observing location of Belfast and covers the month of December)
The Sun
At the start of the month, the Sun rises at 08:25 and sets at 16:00. By month's end, it rises at 08:45 and sets at 16:05.
The Planets
Mercury is at greatest eastern elongation on the 29th. It is visible in the evening sky in the 2nd half of the month. At month's end, it sets at 17:35 and is mag -0.4.
Venus is visible in the morning sky and moves from Virgo to Libra this month. At the start of the month, it rises at 04:05 and by month's end at 05:35. It fades from mag -4.1 to mag -3.9 during the month.
Mars is visible in the morning sky and is in Virgo this month. At the start of the month, it rises at 02:45 and by month's end at 02:30. It brightens from mag +1.5 to mag +1.3 during the month.
Jupiter is at western quadrature on the 14th and becomes a late evening object by month's end. It is in Leo this month. At the start of the month, it rises at 00:50 and by month's end at 23:00. It brightens from mag -1.8 to mag -2.0 during the month.
Saturn is visible in the morning sky by month's end in Ophiuchus when it rises at 06:35 and is mag +1.4.
Uranus is visible in the evening sky in Pisces this month. At the start of the month, it sets at 03:20 and by month's end at 01:20. It maintains its brightness at mag +5.8 during the month and lies to the S of Epsilon (ε) Piscium, mag +4.3.
Neptune is visible in the evening sky in Aquarius this month. At the start of the month, it sets at 23:20 and by month's end at 21:25. It maintains its brightness at mag +7.9 during the month and lies between Lambda (λ) Aquarii, mag +3.7 and Sigma (σ) Aquarii, mag +4.8.
The Moon
The last quarter moon is on the 3rd with the new moon on the 11th. The first quarter moon is on the 18th with the full moon on the 25th.
On the evening of the 1st, the waning gibbous moon lies 6° to the NW of Regulus (Alpha (α) Leonis, mag +1.4) at around midnight.
On the morning of the 4th, the waning crescent moon lies 3° to the W of Jupiter at around 02:00.
On the morning of the 6th, the waning crescent moon lies 3° to the S of Mars at around 04:00.
On the morning of the 7th, the waning crescent moon lies 6° to the E of Spica (Alpha (α) Virginis, mag +1.0) at 05:00. It also lies 8° to the NW of Venus at the same time. On the following morning, it lies 8° to the SE of the planet at the same time.
On the evening of the 16th, the waxing crescent moon lies 8° to the SW of Neptune at around 18:00. On the following evening, it lies 8° to the NE of the planet at the same time.
On the evening of the 19th, the waxing gibbous moon lies 5° to the SW of Uranus at around 18:00.
On the evening of the 23rd, the waxing gibbous moon occults Aldebaran (Alpha (α) Tauri, mag +0.9). The star will disappear behind the lunar disc at around 18:10 and will reappear at 19:10.
On the evening of the 27th, the waning gibbous moon lies 6° to the SW of M44 - The Beehive Cluster at around 20:00.
On the evening of the 29th, the waning gibbous moon lies 8° to the S of Regulus (Alpha (α) Leonis, mag +1.4) at around 22:00.
On the evenings of the 30th and 31st, the waning gibbous moon lies near to Jupiter. It lies to the NW of the planet on the 30th and to the S of it on the following evening. On both evenings, look at around midnight.
Meteors
The best time to observe meteor showers is when the moon is below the horizon; otherwise its bright glare limits the number you will see especially the fainter ones. Below is a guide to this month's showers.
The Geminids peak at 18:00 on the 14th with a ZHR of 120. This means the nights of the 13/14th and the 14th/15th are both good for trying to observe the shower. The radiant is visible from 20:00 and on the night of the 13th; the moon will have already set. On the 14th, the waxing crescent moon sets at 20:50, so a short wait is needed before observing the shower.
They are typically slower meteors than some of the other major showers with a speed of around 35 km/s compared with the Perseids at 59 km/s and the Leonids at 71 km/s.
The Ursids peak at 02:30 on the morning of the 23rd with a ZHR of 10. The radiant is circumpolar, but the waxing gibbous moon in Taurus does not set until 06:00 on the 23rd, leaving only a short observing window for this shower in the dawn skies.
There are additional minor showers this month, details of which can be found at meteorshowersonline.com/calendar.html or www.imo.net/files/data/calendar/cal2015.pdf
Asteroids
Asteroid (16) Psyche is at opposition during daylight hours on the 9th at mag +9.4. It is visible from 19:00 on the evenings of the 8th and 9th in Taurus.
Asteroid (27) Euterpe is at opposition on the morning of the 25th at mag +8.4. It lies to the NW of Propus (Eta (η) Geminorum, mag +3.2). It is visible from 20:00 on the evening of the 24th in Gemini.
Finder charts and further information about the above and other fainter asteroids can be found at; britastro.org/computing/charts_asteroid.html in the source list below.
Comets
Comet C/2013 US10 Catalina will be visible in the morning sky this month. Current estimates have it at mag +6 and it will fade during December. At the start of the month, it may be seen in the morning sky in Virgo at around 07:00. It heads North during the month and is visible by 05:00 at mid-month and by 02:00 by month’s end. On the morning of the 2nd, it lies to the E of Kappa (κ) Virginis, mag +4.2. On the 5th, it lies to the E of Venus. On the 7th, it lies to the NE of Venus and the waning crescent moon. By the 9th, it lies close to Iota (ι) Virginis, mag +4.1 and by month’s end, it lies to the S of Arcturus (Alpha (α) Bootis, mag -0.1).
Finder charts and further information about the above and other fainter comets can be found atwww.aerith.net , cometchasing.skyhound.com, www.ast.cam.ac.uk/%7Ejds/ , in-the-sky.org, www.nightskyhunter.com/index.html in the source list below. Any of the above estimates are based on current information at the time of writing the guide and can be wrong - “Comets are like cats; they have tails, and they do precisely what they want”, David H Levy.
Deep Sky
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. In Andromeda, M31 - The Andromeda galaxy can be observed along with its satellite galaxies M32 and M110. In Perseus, there is the open cluster M34 and the excellent Double Cluster - NGC 869 and 884. In Triangulum, there is the galaxy M33. In Auriga there are three open clusters M36, M37 and M38 and also M35 in Gemini. Taurus has the excellent Pleiades - M45, the Hyades and also M1 - The Crab Nebula. Orion returns to our skies with M42 - The Great Orion Nebula and also Cancer with M44 - The Beehive Cluster.
General Notes
Always keep an eye out for Aurorae. The winter solstice is on the 22nd which sees the shortest day of the year and after this date the nights shorten and the days lengthen. This also sees the beginning of winter. Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein.
The Zodiacal Light can be seen in the West after evening twilight has disappeared or in the East before the morning twilight. The best time of year to see the phenomenon is late-Feb to early-April in the evening sky and September/October in the morning sky - it's then that the ecliptic, along which the cone of the zodiacal light lies, is steepest in our skies. The Gegenschein can be seen in the area of the sky opposite the sun. To view either, you must get yourself to a very dark site to cut out the light pollution. When trying to observe either of these phenomena, it is best to do so when the moon is below the horizon. A new appendix has been added explaining some of the more technical terms used in the guide.
Clear Skies
Neill McKeown
Appendix
The ZHR or Zenithal Hourly Rate is the number of meteors an observer would see in one hour under a clear, dark sky with a limiting apparent magnitude of 6.5 and if the radiant of the shower were in the zenith. The rate that can effectively be seen is nearly always lower and decreases as the radiant is closer to the horizon. The Zenith is the overhead point in the sky.
The radiant is the point in the sky, from which (to a planetary observer) meteors appear to originate, i.e. the Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus. When the radiant is quoted as "circumpolar", it is never below the horizon and visible all night, otherwise the times quoted are when the constellation in which the radiant lies rises above the horizon in the East.
A fireball is defined by the International Astronomical Union as a meteor brighter than any of the planets, i.e. magnitude -4 or brighter. The International Meteor Organisation alternatively defines it as a meteor which would have a magnitude of -3 or brighter at the zenith.
The ° symbol in the guide is that for degrees. A degree is two full moon widths to give an idea for judging any distances quoted in the guide. There are 60 arcminutes in a degree.
An asterism is a collection of stars seen in Earth's sky which form simple patterns which are easy to identify, i.e. the Big Dipper. They can be formed from stars within the same constellation or by stars from more than one constellation. Like the constellations, they are a line of sight phenomenon and the stars whilst visible in the same general direction, are not physically related and are often at significantly different distances from Earth.
Mag is short for magnitude which is the measure of an object's brightness. The smaller the number, the brighter the object. The brightest object in the sky is the Sun at mag -26, the full moon is mag -12 and Venus the brightest planet is mag -4. The brightest stars are mag -1. If there is a 1 mag difference between two objects - there is a difference in brightness of a factor of 2.5 between the two objects. For example the full moon is eight magnitudes brighter than Venus on average which means it is 1,526 times brighter than Venus. Objects down to mag +6 can be seen with the naked eye under very dark skies.
Local time is always quoted in the guide and this means for November - February - universal time (UT)/GMT is used and for April to September - daylight savings time (DST, = GMT+1). For the months of March and October when the clocks go forward/back respectively, both times will be used and attention should be paid to any times at the end of these months for that change.
Deep Sky Objects such as galaxies, nebulae and star clusters are classified in catalogues such as the Messier catalogue for objects like M44 - M for Messier. Another example of a catalogue would the New General catalogue whose objects have the prefix NGC. There are links for websites to both catalogues in the section above.
Perihelion is the point in the orbit of a planet, asteroid or comet where it is at the nearest point in its orbit to the sun. It is the opposite of Aphelion, which is when the object is at the farthest point in its orbit from the sun. For the earth, the comparative terms used are perigee and apogee and for the moon, pericynthion and apocynthion are sometimes used.
The Planets
From Earth - Mercury and Venus are the inner planets in the solar system and Mars, Jupiter, Saturn, Uranus and Neptune are the outer planets. Below is a short guide as to how both the inner and outer planets move around the sun. The above pictorial guide should hopefully help in this.
The Inner Planets
These are best seen when at Greatest Eastern/Western elongation and are not visible when at either Inferior/Superior conjunction. Greatest Eastern elongation is when the inner planet is at its furthest point east from the sun as seen from Earth and visible in the evening sky in the West after sunset, Western elongation is when it's at its furthest point west from the sun as seen from Earth and visible in the morning sky in the East before sunrise. Inferior conjunction occurs when the inner planet is between the Sun and the Earth. Superior conjunction occurs when the inner planet is on the other side of the Sun as seen from Earth.
From our Northerly latitudes, the ecliptic, along which the planets move, lies at a very shallow angle to the horizon after sunset in the autumn and before sunrise in the spring. This means that any of the planets will be difficult to see when fairly close to the Sun in the evening sky in the autumn or in the morning sky in the spring. In particular, Mercury is more or less invisible from here when at Eastern elongation in the autumn or at Western elongation in the spring, because it lies so close to the horizon and is never above the horizon except in daylight or bright twilight.
The normal cycle for an inner planet is Superior Conjunction - Greatest Eastern Elongation - Inferior Conjunction - Greatest Western Elongation - Superior Conjunction. After superior conjunction, the planet moves away from the Sun as seen from Earth and becomes visible in the evening sky after a period of time. It then moves past the point of Greatest Eastern Elongation and moves back towards the Sun as seen from Earth until a point when it is not visible and at Inferior Conjunction. After this the planet appears in the morning sky for a time, before again slipping into the Sun's glare as seen from Earth. The duration of this cycle will depend on the planet's closeness to the Sun, i.e. Mercury completes the above cycle in around 4 months.
The Outer Planets
These are best seen when at opposition and are not visible when at conjunction. Opposition occurs when the earth is between the sun and the outer planet. It is the best time to observe them because the planet is visible all through the night and it is due South and at its highest at about midnight. The planet is also at its closest point in its orbit to Earth - making it appear brighter. Conjunction occurs when the outer planet is on the other side of the Sun as seen from Earth.
If the planet is at or near it furthest point South along the ecliptic, then it won't get very high in the sky even at opposition - just as the Sun never gets high in the sky in midwinter. This happens when opposition occurs near midsummer when the planet is opposite the Sun in the sky and in midsummer the Sun is high, so the planet will be low. The opposite of course applies in winter.
The normal cycle for an outer planet is Conjunction - Western Quadrature - Opposition - Eastern Quadrature - Conjunction. After conjunction, the planet moves away from the Sun as seen from Earth and becomes visible again. The planet from this point on rises earlier and earlier in the morning sky and eventually becomes visible in the evening sky. At Western Quadrature it is at its highest at sunrise and by opposition it is in the same position by midnight. By Eastern Quadrature, it is past its best and is at its highest at sunset, meaning it is rising in daytime and setting earlier and earlier until a point when it sets too close to the Sun as seen from Earth and is no longer visible. The duration of this cycle will depend on the planet's closeness to the Sun, i.e. Jupiter completes the above cycle in around 13-14 months.
(Please note all times are UT and are based on an observing location of Belfast and covers the month of December)
The Sun
At the start of the month, the Sun rises at 08:25 and sets at 16:00. By month's end, it rises at 08:45 and sets at 16:05.
The Planets
Mercury is at greatest eastern elongation on the 29th. It is visible in the evening sky in the 2nd half of the month. At month's end, it sets at 17:35 and is mag -0.4.
Venus is visible in the morning sky and moves from Virgo to Libra this month. At the start of the month, it rises at 04:05 and by month's end at 05:35. It fades from mag -4.1 to mag -3.9 during the month.
Mars is visible in the morning sky and is in Virgo this month. At the start of the month, it rises at 02:45 and by month's end at 02:30. It brightens from mag +1.5 to mag +1.3 during the month.
Jupiter is at western quadrature on the 14th and becomes a late evening object by month's end. It is in Leo this month. At the start of the month, it rises at 00:50 and by month's end at 23:00. It brightens from mag -1.8 to mag -2.0 during the month.
Saturn is visible in the morning sky by month's end in Ophiuchus when it rises at 06:35 and is mag +1.4.
Uranus is visible in the evening sky in Pisces this month. At the start of the month, it sets at 03:20 and by month's end at 01:20. It maintains its brightness at mag +5.8 during the month and lies to the S of Epsilon (ε) Piscium, mag +4.3.
Neptune is visible in the evening sky in Aquarius this month. At the start of the month, it sets at 23:20 and by month's end at 21:25. It maintains its brightness at mag +7.9 during the month and lies between Lambda (λ) Aquarii, mag +3.7 and Sigma (σ) Aquarii, mag +4.8.
The Moon
The last quarter moon is on the 3rd with the new moon on the 11th. The first quarter moon is on the 18th with the full moon on the 25th.
On the evening of the 1st, the waning gibbous moon lies 6° to the NW of Regulus (Alpha (α) Leonis, mag +1.4) at around midnight.
On the morning of the 4th, the waning crescent moon lies 3° to the W of Jupiter at around 02:00.
On the morning of the 6th, the waning crescent moon lies 3° to the S of Mars at around 04:00.
On the morning of the 7th, the waning crescent moon lies 6° to the E of Spica (Alpha (α) Virginis, mag +1.0) at 05:00. It also lies 8° to the NW of Venus at the same time. On the following morning, it lies 8° to the SE of the planet at the same time.
On the evening of the 16th, the waxing crescent moon lies 8° to the SW of Neptune at around 18:00. On the following evening, it lies 8° to the NE of the planet at the same time.
On the evening of the 19th, the waxing gibbous moon lies 5° to the SW of Uranus at around 18:00.
On the evening of the 23rd, the waxing gibbous moon occults Aldebaran (Alpha (α) Tauri, mag +0.9). The star will disappear behind the lunar disc at around 18:10 and will reappear at 19:10.
On the evening of the 27th, the waning gibbous moon lies 6° to the SW of M44 - The Beehive Cluster at around 20:00.
On the evening of the 29th, the waning gibbous moon lies 8° to the S of Regulus (Alpha (α) Leonis, mag +1.4) at around 22:00.
On the evenings of the 30th and 31st, the waning gibbous moon lies near to Jupiter. It lies to the NW of the planet on the 30th and to the S of it on the following evening. On both evenings, look at around midnight.
Meteors
The best time to observe meteor showers is when the moon is below the horizon; otherwise its bright glare limits the number you will see especially the fainter ones. Below is a guide to this month's showers.
The Geminids peak at 18:00 on the 14th with a ZHR of 120. This means the nights of the 13/14th and the 14th/15th are both good for trying to observe the shower. The radiant is visible from 20:00 and on the night of the 13th; the moon will have already set. On the 14th, the waxing crescent moon sets at 20:50, so a short wait is needed before observing the shower.
They are typically slower meteors than some of the other major showers with a speed of around 35 km/s compared with the Perseids at 59 km/s and the Leonids at 71 km/s.
The Ursids peak at 02:30 on the morning of the 23rd with a ZHR of 10. The radiant is circumpolar, but the waxing gibbous moon in Taurus does not set until 06:00 on the 23rd, leaving only a short observing window for this shower in the dawn skies.
There are additional minor showers this month, details of which can be found at meteorshowersonline.com/calendar.html or www.imo.net/files/data/calendar/cal2015.pdf
Asteroids
Asteroid (16) Psyche is at opposition during daylight hours on the 9th at mag +9.4. It is visible from 19:00 on the evenings of the 8th and 9th in Taurus.
Asteroid (27) Euterpe is at opposition on the morning of the 25th at mag +8.4. It lies to the NW of Propus (Eta (η) Geminorum, mag +3.2). It is visible from 20:00 on the evening of the 24th in Gemini.
Finder charts and further information about the above and other fainter asteroids can be found at; britastro.org/computing/charts_asteroid.html in the source list below.
Comets
Comet C/2013 US10 Catalina will be visible in the morning sky this month. Current estimates have it at mag +6 and it will fade during December. At the start of the month, it may be seen in the morning sky in Virgo at around 07:00. It heads North during the month and is visible by 05:00 at mid-month and by 02:00 by month’s end. On the morning of the 2nd, it lies to the E of Kappa (κ) Virginis, mag +4.2. On the 5th, it lies to the E of Venus. On the 7th, it lies to the NE of Venus and the waning crescent moon. By the 9th, it lies close to Iota (ι) Virginis, mag +4.1 and by month’s end, it lies to the S of Arcturus (Alpha (α) Bootis, mag -0.1).
Finder charts and further information about the above and other fainter comets can be found atwww.aerith.net , cometchasing.skyhound.com, www.ast.cam.ac.uk/%7Ejds/ , in-the-sky.org, www.nightskyhunter.com/index.html in the source list below. Any of the above estimates are based on current information at the time of writing the guide and can be wrong - “Comets are like cats; they have tails, and they do precisely what they want”, David H Levy.
Deep Sky
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. In Andromeda, M31 - The Andromeda galaxy can be observed along with its satellite galaxies M32 and M110. In Perseus, there is the open cluster M34 and the excellent Double Cluster - NGC 869 and 884. In Triangulum, there is the galaxy M33. In Auriga there are three open clusters M36, M37 and M38 and also M35 in Gemini. Taurus has the excellent Pleiades - M45, the Hyades and also M1 - The Crab Nebula. Orion returns to our skies with M42 - The Great Orion Nebula and also Cancer with M44 - The Beehive Cluster.
General Notes
Always keep an eye out for Aurorae. The winter solstice is on the 22nd which sees the shortest day of the year and after this date the nights shorten and the days lengthen. This also sees the beginning of winter. Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein.
The Zodiacal Light can be seen in the West after evening twilight has disappeared or in the East before the morning twilight. The best time of year to see the phenomenon is late-Feb to early-April in the evening sky and September/October in the morning sky - it's then that the ecliptic, along which the cone of the zodiacal light lies, is steepest in our skies. The Gegenschein can be seen in the area of the sky opposite the sun. To view either, you must get yourself to a very dark site to cut out the light pollution. When trying to observe either of these phenomena, it is best to do so when the moon is below the horizon. A new appendix has been added explaining some of the more technical terms used in the guide.
Clear Skies
Neill McKeown
Appendix
The ZHR or Zenithal Hourly Rate is the number of meteors an observer would see in one hour under a clear, dark sky with a limiting apparent magnitude of 6.5 and if the radiant of the shower were in the zenith. The rate that can effectively be seen is nearly always lower and decreases as the radiant is closer to the horizon. The Zenith is the overhead point in the sky.
The radiant is the point in the sky, from which (to a planetary observer) meteors appear to originate, i.e. the Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus. When the radiant is quoted as "circumpolar", it is never below the horizon and visible all night, otherwise the times quoted are when the constellation in which the radiant lies rises above the horizon in the East.
A fireball is defined by the International Astronomical Union as a meteor brighter than any of the planets, i.e. magnitude -4 or brighter. The International Meteor Organisation alternatively defines it as a meteor which would have a magnitude of -3 or brighter at the zenith.
The ° symbol in the guide is that for degrees. A degree is two full moon widths to give an idea for judging any distances quoted in the guide. There are 60 arcminutes in a degree.
An asterism is a collection of stars seen in Earth's sky which form simple patterns which are easy to identify, i.e. the Big Dipper. They can be formed from stars within the same constellation or by stars from more than one constellation. Like the constellations, they are a line of sight phenomenon and the stars whilst visible in the same general direction, are not physically related and are often at significantly different distances from Earth.
Mag is short for magnitude which is the measure of an object's brightness. The smaller the number, the brighter the object. The brightest object in the sky is the Sun at mag -26, the full moon is mag -12 and Venus the brightest planet is mag -4. The brightest stars are mag -1. If there is a 1 mag difference between two objects - there is a difference in brightness of a factor of 2.5 between the two objects. For example the full moon is eight magnitudes brighter than Venus on average which means it is 1,526 times brighter than Venus. Objects down to mag +6 can be seen with the naked eye under very dark skies.
Local time is always quoted in the guide and this means for November - February - universal time (UT)/GMT is used and for April to September - daylight savings time (DST, = GMT+1). For the months of March and October when the clocks go forward/back respectively, both times will be used and attention should be paid to any times at the end of these months for that change.
Deep Sky Objects such as galaxies, nebulae and star clusters are classified in catalogues such as the Messier catalogue for objects like M44 - M for Messier. Another example of a catalogue would the New General catalogue whose objects have the prefix NGC. There are links for websites to both catalogues in the section above.
Perihelion is the point in the orbit of a planet, asteroid or comet where it is at the nearest point in its orbit to the sun. It is the opposite of Aphelion, which is when the object is at the farthest point in its orbit from the sun. For the earth, the comparative terms used are perigee and apogee and for the moon, pericynthion and apocynthion are sometimes used.
The Planets
From Earth - Mercury and Venus are the inner planets in the solar system and Mars, Jupiter, Saturn, Uranus and Neptune are the outer planets. Below is a short guide as to how both the inner and outer planets move around the sun. The above pictorial guide should hopefully help in this.
The Inner Planets
These are best seen when at Greatest Eastern/Western elongation and are not visible when at either Inferior/Superior conjunction. Greatest Eastern elongation is when the inner planet is at its furthest point east from the sun as seen from Earth and visible in the evening sky in the West after sunset, Western elongation is when it's at its furthest point west from the sun as seen from Earth and visible in the morning sky in the East before sunrise. Inferior conjunction occurs when the inner planet is between the Sun and the Earth. Superior conjunction occurs when the inner planet is on the other side of the Sun as seen from Earth.
From our Northerly latitudes, the ecliptic, along which the planets move, lies at a very shallow angle to the horizon after sunset in the autumn and before sunrise in the spring. This means that any of the planets will be difficult to see when fairly close to the Sun in the evening sky in the autumn or in the morning sky in the spring. In particular, Mercury is more or less invisible from here when at Eastern elongation in the autumn or at Western elongation in the spring, because it lies so close to the horizon and is never above the horizon except in daylight or bright twilight.
The normal cycle for an inner planet is Superior Conjunction - Greatest Eastern Elongation - Inferior Conjunction - Greatest Western Elongation - Superior Conjunction. After superior conjunction, the planet moves away from the Sun as seen from Earth and becomes visible in the evening sky after a period of time. It then moves past the point of Greatest Eastern Elongation and moves back towards the Sun as seen from Earth until a point when it is not visible and at Inferior Conjunction. After this the planet appears in the morning sky for a time, before again slipping into the Sun's glare as seen from Earth. The duration of this cycle will depend on the planet's closeness to the Sun, i.e. Mercury completes the above cycle in around 4 months.
The Outer Planets
These are best seen when at opposition and are not visible when at conjunction. Opposition occurs when the earth is between the sun and the outer planet. It is the best time to observe them because the planet is visible all through the night and it is due South and at its highest at about midnight. The planet is also at its closest point in its orbit to Earth - making it appear brighter. Conjunction occurs when the outer planet is on the other side of the Sun as seen from Earth.
If the planet is at or near it furthest point South along the ecliptic, then it won't get very high in the sky even at opposition - just as the Sun never gets high in the sky in midwinter. This happens when opposition occurs near midsummer when the planet is opposite the Sun in the sky and in midsummer the Sun is high, so the planet will be low. The opposite of course applies in winter.
The normal cycle for an outer planet is Conjunction - Western Quadrature - Opposition - Eastern Quadrature - Conjunction. After conjunction, the planet moves away from the Sun as seen from Earth and becomes visible again. The planet from this point on rises earlier and earlier in the morning sky and eventually becomes visible in the evening sky. At Western Quadrature it is at its highest at sunrise and by opposition it is in the same position by midnight. By Eastern Quadrature, it is past its best and is at its highest at sunset, meaning it is rising in daytime and setting earlier and earlier until a point when it sets too close to the Sun as seen from Earth and is no longer visible. The duration of this cycle will depend on the planet's closeness to the Sun, i.e. Jupiter completes the above cycle in around 13-14 months.
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9 years 3 weeks ago #105150
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Replied by Neill on topic December 15 Observing Guide
Information Sources Used and Links
Sky at Night Magazine Observing Guide; IFAS Calendar 2015; www.aerith.net;cometchasing.skyhound.com ; www.ast.cam.ac.uk/%7Ejds/ ; Stardust Magazine; britastro.org/computing/charts_asteroid.html ; in-the-sky.org ; www.nightskyhunter.com/index.html ; www.ea...me.uk/Sky/Wordpress/; eco.mtk.nao.ac.jp/cgi-bin/koyomi/cande/phenomena_en.cgi;
Philip's Stargazing 2015; Patrick Moore's 2015 Yearbook of Astronomy; www.heavens-above.com;www.spaceweather.com ;meteorshowersonline.com/calendar.html ; www.timeanddate.com/astronomy/;http://ww...calendar/cal2015.pdf - International Meteor Organisation; messier.seds.org/ - The Messier Catalogue website; www.seds.org/messier/xtra/ngc/ngc.html - NGC Catalogue website; www.irishastronomy.org - Irish Federation of Astronomy Societies Website; irishastro.org.uk/- Irish Astronomical Association website; www.eaas.co.uk - Northern Ireland Amateur Astronomy Society;
Sky at Night Magazine Observing Guide; IFAS Calendar 2015; www.aerith.net;cometchasing.skyhound.com ; www.ast.cam.ac.uk/%7Ejds/ ; Stardust Magazine; britastro.org/computing/charts_asteroid.html ; in-the-sky.org ; www.nightskyhunter.com/index.html ; www.ea...me.uk/Sky/Wordpress/; eco.mtk.nao.ac.jp/cgi-bin/koyomi/cande/phenomena_en.cgi;
Philip's Stargazing 2015; Patrick Moore's 2015 Yearbook of Astronomy; www.heavens-above.com;www.spaceweather.com ;meteorshowersonline.com/calendar.html ; www.timeanddate.com/astronomy/;http://ww...calendar/cal2015.pdf - International Meteor Organisation; messier.seds.org/ - The Messier Catalogue website; www.seds.org/messier/xtra/ngc/ngc.html - NGC Catalogue website; www.irishastronomy.org - Irish Federation of Astronomy Societies Website; irishastro.org.uk/- Irish Astronomical Association website; www.eaas.co.uk - Northern Ireland Amateur Astronomy Society;
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9 years 3 weeks ago #105151
by lunartic_old
Programming today is a race between software engineers striving to build bigger and better programs, and the universe trying to produce bigger and better idiots. So far, the universe is winning.
Rich Cook
Replied by lunartic_old on topic December 15 Observing Guide
There are some nice moon events upcoming that will be worth a look.
Paul
Paul
Programming today is a race between software engineers striving to build bigger and better programs, and the universe trying to produce bigger and better idiots. So far, the universe is winning.
Rich Cook
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