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July 14 Observing Guide
- Neill
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10 years 5 months ago #101058
by Neill
July 14 Observing Guide was created by Neill
OBSERVING GUIDE
(Please note all times are ST and are based on an observing location of Belfast and covers the month of July)
The Sun
At the start of the month, the Sun rises at 04:55 and sets at 22:00. By month's end, it rises at 05:35 and sets at 21:25.
The Planets
Mercury is at greatest western elongation on the 12th and is visible in the second half of the month in the morning sky. On the 12th, it rises at 03:55 and is mag +0.5. At month's end it rises at 04:40 and is mag -1.4.
Venus is a morning object during the month. At start of the month, it rises at 03:15 and by month's end, it rises at 03:35. It maintains its brightness at mag -3.9 during the month.
Mars is at eastern quadrature on the 19th and is visible in the evening sky in Virgo this month. During the month, it rises during daylight hours and sets at 23:25 by month's end. It fades from mag +0.0 to mag +0.4 during the month. It lies near to Spica (Alpha (α) Virginis, mag +1.0) during the month.
Jupiter is at conjunction on the 24th and is not visible this month.
Saturn is visible in the evening sky in Libra. It rises during daylight hours during the month and sets at 00:20 by month's end. It fades from mag +0.4 to mag +0.5 during the month.
Uranus is at western quadrature on the 8th and is visible in the morning sky in Pisces this month. At the start of the month, it rises at 01:15 and by month's end, at 23:15. It maintains its brightness at mag +5.8 and lies 2° S of Kaht (Epsilon (ε) Piscium, mag +4.3) during the month.
Neptune is visible in the morning sky in Aquarius this month. At the start of the month, it rises at 00:20 and by month's end, at 22:20. It brightens from mag +7.9 to mag +7.8 and lies 2° to the NE of Sigma (σ) Aquarii, mag +4.8 during the month.
The Moon
The first quarter moon is on the 5th with the full moon on the 12th and the last quarter moon on the 19th. The new moon is on the 26th.
On the evening of the 1st, the waxing crescent moon lies to the S of Regulus (Alpha (α) Leonis, mag +1.4) at around 23:00.
On the evenings of the 5th and 6th, the waxing gibbous moon lies near to Mars and Spica (Alpha (α) Virginis, mag +1.0). On the 5th, it lies 3° to the SW of the planet and 6° to the W of the star. On the 6th, it lies 8° to the NE of the star and to the E of the planet. On both evenings, look at around 23:00.
On the evening of the 7th, the waxing gibbous moon lies 4° to the SW of Saturn and 1° to the NW of Zubenelgenubi (Alpha (α) Librae, mag +2.
at around midnight.
On the evening of the 9th, the waxing gibbous moon lies to the NW of Antares (Alpha (α) Scorpii, mag +1.0) at around midnight.
On the morning of the 16th, the waning gibbous moon lies 7° to the NE of Neptune at around 01:00.
On the morning of the 18th, the waning gibbous moon lies 5° to the NW of Uranus at around 01:00.
On the morning of the 21st, the waning crescent moon lies to the SW of M45 - The Pleiades at around 03:00.
On the mornings of the 22nd and 23rd, the waning crescent moon lies near to Aldebaran (Alpha (α) Tauri, mag +0.9). On the 22nd, it lies 7° to the NW of the star and on the 23rd, it lies 8° to the SE of it. On both mornings, look at around 04:00.
On the morning of the 24th, the waning crescent moon lies 8° to the W of Venus at around 04:00.
On the morning of the 25th, the waning crescent moon lies 7° to the SW of Mercury at around 05:00.
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 Southern Delta Aquarids peak on the 30th. The ZHR is 16 and the radiant is visible from about midnight on the evenings of the 29th and 30th. The moon sets before the radiant is visible so conditions are good for observing this shower.
There are additional minor showers this month, details of which can be found at meteorshowersonline.com/calendar.html or www.imo.net/calendar/2014
Asteroids
There are no bright asteroids at opposition this month.
Finder charts and further information about other fainter asteroids can be found at; britastro.org/computing/charts_asteroid.html in the source list below.
Comets
C/2012 K1 (Panstarrs) is currently mag +8 and brightening as the year progresses. In July, it is in Leo all month. It sets at 01:00 at the start of the month, at midnight mid-month and at 22:00 by month's end.
C/2014 E2 (Jacques) is at perihelion on the 2nd with it expected to peak at mag +6. It becomes visible as a morning comet in the second half of the month. It starts the month in Taurus before heading N into Auriga. At mid-month, it is visible from 03:00 and by month's end from 01:00. On the 13th, it passes near to Venus, on the 20th, it passes near to Elnath (Beta (β) Tauri, mag +1.7) and by month's end lies to the NE of Al Kab (Iota (ι) Aurigae, mag +2.7).
C/2013 UQ4 (Catalina) is currently mag +11, but is at perihelion on the 6th with it predicted to peak at mag +7. At the start of the month, it passes 1° from Alpheratz (Alpha (α) Andromedae, mag +2.1), it then heads N through Lacerta and Cepheus, passing 1° from Eta (η) and Theta (θ) Cephei, mag +3.4 and +4.2 respectively on the 10th. It reaches Draco by mid-month. It gets to Bootes in the last week of the month. It is visible from midnight at the start of the month, is circumpolar mid-month and sets at 04:00 by month's end.
Finder charts and further information about other fainter comets can be found at www.aerith.net , cometchasing.skyhound.com , www.ast.cam.ac.uk/%7Ejds/ , in-the-sky.org , kometen.fg-vds.de/fgk_hpe.htm, www.nightskyhunter.com/index.html and www.rasnz.org.nz in the source list below. Any above estimates for predicting a comet's brightness/status are based on current information at the time of writing the guide and the comet may be brighter/dimmer than the above predictions or may no longer be intact to observe.
Deep Sky
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. Check out the constellation Canes Venatici with the globular cluster - M3 and several galaxies including M51 - the Whirlpool Galaxy and M63 - the Sunflower Galaxy. In Hercules, two globular clusters - M92 and the excellent M13 can be observed and in Lyra - M57 - The Ring Nebula can be observed. In Vulpecula - M27 - The Dumbbell Nebula can be found. 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. Finally in Triangulum, there is the galaxy M33.
General Notes
Always keep an eye out for Aurorae. The night sky does not get fully dark this month. Between May and the middle of August, Astronomical twilight is present at night. This is when the sun is between twelve and eighteen degrees below the horizon. This time of year is very good for observing the numerous satellites and other objects in orbit above us.
Watch out for NLCs - Noctilucent Clouds during July. They are mostly visible between the Northern latitudes of 50 to 65 degrees. Look to the North-West for a white/silvery glow with the best times between 22:30 and Midnight and between 02:00 and 03:30. They can sometimes be faint, sometimes bright. Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein. Both are caused by sunlight reflecting off dust particles which are present in the solar system.
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
Information Sources Used and Links
www.skyviewcafe.com ; Sky at Night Magazine Observing Guide and CD; www.aerith.net ; cometchasing.skyhound.com ; www.ast.cam.ac.uk/%7Ejds/ ; kometen.fg-vds.de/fgk_hpe.htm ; www.rasnz.org.nz ; Stardust Magazine; britastro.org/computing/charts_asteroid.html ; in-the-sky.org ; www.nightskyhunter.com/index.html www.eagleseye.me.uk/Sky/Wordpress/;http:...meris/ephemeris.html ; eco.mtk.nao.ac.jp/cgi-bin/koyomi/cande/phenomena_en.cgi ;
Philip's Stargazing 2014; Patrick Moore's 2014 Yearbook of Astronomy; www.heavens-above.com ; www.spaceweather.com ;meteorshowersonline.com/calendar.html ; www.timeanddate.com/astronomy/ ; www.imo.net/calendar/2014 - 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;
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 sunset. 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 ST and are based on an observing location of Belfast and covers the month of July)
The Sun
At the start of the month, the Sun rises at 04:55 and sets at 22:00. By month's end, it rises at 05:35 and sets at 21:25.
The Planets
Mercury is at greatest western elongation on the 12th and is visible in the second half of the month in the morning sky. On the 12th, it rises at 03:55 and is mag +0.5. At month's end it rises at 04:40 and is mag -1.4.
Venus is a morning object during the month. At start of the month, it rises at 03:15 and by month's end, it rises at 03:35. It maintains its brightness at mag -3.9 during the month.
Mars is at eastern quadrature on the 19th and is visible in the evening sky in Virgo this month. During the month, it rises during daylight hours and sets at 23:25 by month's end. It fades from mag +0.0 to mag +0.4 during the month. It lies near to Spica (Alpha (α) Virginis, mag +1.0) during the month.
Jupiter is at conjunction on the 24th and is not visible this month.
Saturn is visible in the evening sky in Libra. It rises during daylight hours during the month and sets at 00:20 by month's end. It fades from mag +0.4 to mag +0.5 during the month.
Uranus is at western quadrature on the 8th and is visible in the morning sky in Pisces this month. At the start of the month, it rises at 01:15 and by month's end, at 23:15. It maintains its brightness at mag +5.8 and lies 2° S of Kaht (Epsilon (ε) Piscium, mag +4.3) during the month.
Neptune is visible in the morning sky in Aquarius this month. At the start of the month, it rises at 00:20 and by month's end, at 22:20. It brightens from mag +7.9 to mag +7.8 and lies 2° to the NE of Sigma (σ) Aquarii, mag +4.8 during the month.
The Moon
The first quarter moon is on the 5th with the full moon on the 12th and the last quarter moon on the 19th. The new moon is on the 26th.
On the evening of the 1st, the waxing crescent moon lies to the S of Regulus (Alpha (α) Leonis, mag +1.4) at around 23:00.
On the evenings of the 5th and 6th, the waxing gibbous moon lies near to Mars and Spica (Alpha (α) Virginis, mag +1.0). On the 5th, it lies 3° to the SW of the planet and 6° to the W of the star. On the 6th, it lies 8° to the NE of the star and to the E of the planet. On both evenings, look at around 23:00.
On the evening of the 7th, the waxing gibbous moon lies 4° to the SW of Saturn and 1° to the NW of Zubenelgenubi (Alpha (α) Librae, mag +2.
at around midnight.On the evening of the 9th, the waxing gibbous moon lies to the NW of Antares (Alpha (α) Scorpii, mag +1.0) at around midnight.
On the morning of the 16th, the waning gibbous moon lies 7° to the NE of Neptune at around 01:00.
On the morning of the 18th, the waning gibbous moon lies 5° to the NW of Uranus at around 01:00.
On the morning of the 21st, the waning crescent moon lies to the SW of M45 - The Pleiades at around 03:00.
On the mornings of the 22nd and 23rd, the waning crescent moon lies near to Aldebaran (Alpha (α) Tauri, mag +0.9). On the 22nd, it lies 7° to the NW of the star and on the 23rd, it lies 8° to the SE of it. On both mornings, look at around 04:00.
On the morning of the 24th, the waning crescent moon lies 8° to the W of Venus at around 04:00.
On the morning of the 25th, the waning crescent moon lies 7° to the SW of Mercury at around 05:00.
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 Southern Delta Aquarids peak on the 30th. The ZHR is 16 and the radiant is visible from about midnight on the evenings of the 29th and 30th. The moon sets before the radiant is visible so conditions are good for observing this shower.
There are additional minor showers this month, details of which can be found at meteorshowersonline.com/calendar.html or www.imo.net/calendar/2014
Asteroids
There are no bright asteroids at opposition this month.
Finder charts and further information about other fainter asteroids can be found at; britastro.org/computing/charts_asteroid.html in the source list below.
Comets
C/2012 K1 (Panstarrs) is currently mag +8 and brightening as the year progresses. In July, it is in Leo all month. It sets at 01:00 at the start of the month, at midnight mid-month and at 22:00 by month's end.
C/2014 E2 (Jacques) is at perihelion on the 2nd with it expected to peak at mag +6. It becomes visible as a morning comet in the second half of the month. It starts the month in Taurus before heading N into Auriga. At mid-month, it is visible from 03:00 and by month's end from 01:00. On the 13th, it passes near to Venus, on the 20th, it passes near to Elnath (Beta (β) Tauri, mag +1.7) and by month's end lies to the NE of Al Kab (Iota (ι) Aurigae, mag +2.7).
C/2013 UQ4 (Catalina) is currently mag +11, but is at perihelion on the 6th with it predicted to peak at mag +7. At the start of the month, it passes 1° from Alpheratz (Alpha (α) Andromedae, mag +2.1), it then heads N through Lacerta and Cepheus, passing 1° from Eta (η) and Theta (θ) Cephei, mag +3.4 and +4.2 respectively on the 10th. It reaches Draco by mid-month. It gets to Bootes in the last week of the month. It is visible from midnight at the start of the month, is circumpolar mid-month and sets at 04:00 by month's end.
Finder charts and further information about other fainter comets can be found at www.aerith.net , cometchasing.skyhound.com , www.ast.cam.ac.uk/%7Ejds/ , in-the-sky.org , kometen.fg-vds.de/fgk_hpe.htm, www.nightskyhunter.com/index.html and www.rasnz.org.nz in the source list below. Any above estimates for predicting a comet's brightness/status are based on current information at the time of writing the guide and the comet may be brighter/dimmer than the above predictions or may no longer be intact to observe.
Deep Sky
On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. Check out the constellation Canes Venatici with the globular cluster - M3 and several galaxies including M51 - the Whirlpool Galaxy and M63 - the Sunflower Galaxy. In Hercules, two globular clusters - M92 and the excellent M13 can be observed and in Lyra - M57 - The Ring Nebula can be observed. In Vulpecula - M27 - The Dumbbell Nebula can be found. 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. Finally in Triangulum, there is the galaxy M33.
General Notes
Always keep an eye out for Aurorae. The night sky does not get fully dark this month. Between May and the middle of August, Astronomical twilight is present at night. This is when the sun is between twelve and eighteen degrees below the horizon. This time of year is very good for observing the numerous satellites and other objects in orbit above us.
Watch out for NLCs - Noctilucent Clouds during July. They are mostly visible between the Northern latitudes of 50 to 65 degrees. Look to the North-West for a white/silvery glow with the best times between 22:30 and Midnight and between 02:00 and 03:30. They can sometimes be faint, sometimes bright. Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein. Both are caused by sunlight reflecting off dust particles which are present in the solar system.
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
Information Sources Used and Links
www.skyviewcafe.com ; Sky at Night Magazine Observing Guide and CD; www.aerith.net ; cometchasing.skyhound.com ; www.ast.cam.ac.uk/%7Ejds/ ; kometen.fg-vds.de/fgk_hpe.htm ; www.rasnz.org.nz ; Stardust Magazine; britastro.org/computing/charts_asteroid.html ; in-the-sky.org ; www.nightskyhunter.com/index.html www.eagleseye.me.uk/Sky/Wordpress/;http:...meris/ephemeris.html ; eco.mtk.nao.ac.jp/cgi-bin/koyomi/cande/phenomena_en.cgi ;
Philip's Stargazing 2014; Patrick Moore's 2014 Yearbook of Astronomy; www.heavens-above.com ; www.spaceweather.com ;meteorshowersonline.com/calendar.html ; www.timeanddate.com/astronomy/ ; www.imo.net/calendar/2014 - 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;
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 sunset. 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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