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Astronomical Information for Taunton during June 2018

Starfish imageIntroduction


Welcome to StarFish.net – Astronomical Information from the UK Hydrographic Office ...

This page provides some astronomical information on a monthly basis for those of you living in the Taunton area. Timings are in BST (British Summer Time) unless otherwise noted. Latest additions or updates are highlighted with a red border.

This month we have sections on:


2018 Astronomical and Calendarial Sheet

Download Adobe Acrobat Reader Additional information on phases of the Moon, seasons, summer times, eclipses, chronological cycles and eras, religious holidays, the United Kingdom civil calendar and holiday dates can be found in HMNAO's Astronomical and Calendarial Sheet for 2018. This is a pdf document for which a document reader can be downloaded by clicking on the Adobe Reader icon above.

Remember ...

This web page can also be accessed from outside the UK Hydrographic Office on http://astro.ukho.gov.uk/nao/taunton.html.

↻ The last update to this page was made on Friday, 2018 June 22 at 08:55:34 BST.


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Starfish imageSolstices & Equinoxes


Solstices and Equinoxes diagram courtesy NASA (357x432) The Summer Solstice for the northern hemisphere (or the Winter Solstice for the southern hemisphere) takes place on Thursday June 21st at 11:07 BST. The word "solstice" comes from the latin for Sun (Sol) and to stand still (sistere) and refers to the fact that the Sun has reached its maximum declination north in the case of the Summer Solstice. Put another way, the Sun has reached the highest daily maximum altitude it can attain when due south in the northern hemisphere. For Taunton, at local noon, the Sun reaches a maximum altitude of 62.4°. Please click on the image to see a larger version of the above diagram.


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Starfish imageThe Sun


28-day animation of Solar Dynamics Observatory images of the Sun courtesy of NASA An animated view of the Sun's disk over the last twenty-eight days is shown in the image on the left. North is at the top of the image and east is to the left. These images come from the Helioseismic and Magnetic Imager instrument on the NASA Solar Dynamics Observatory (SDO) satellite. More multi-wavelength data from the SDO can be found here.

Active region AR2713 is approaching the western limb of the Sun and shows little evidence for significant solar flare activity. Active region AR2714, a multi-cored feature, is about to cross the western limb of the Sun. It, too, is incapable of supporting significant solar flare activity. A third active region, AR2715, recently appeared in the eastern hemisphere of the Sun and is now approaching the centre of the disk. It has two dark cores and has quadrupled in size in the last 48 hours. It could pose a threat for more minor C-class solar flares similar to the C2-class event observed at 01:15 UT on June 21st. The resulting pulse of ultraviolet radiation ionised the top of the Earth's atmosphere over the Pacific Ocean causing shortwave radio disruption at frequencies below 10Mhz. The total number of spotless days for 2018 remains fixed at 87, or 50% of the year so far. There is a coronal hole surrounding the north pole of the Sun extending southwards along the Sun's central meridian. A reasonably dense stream of solar wind, moving at around 350km/s, is emanating from this feature. The Earth is immersed in this stream which may lead to further minor G1-class geomagnetic activity in the next day or so. Canadian observers have already experienced simultaneous auroral and noctilucent cloud displays on the night of June 18th/19th in Alberta. Observers in the polar regions, particularly those under the darker skies of the southern hemisphere, are best-placed to observe any auroral displays. Overall solar activity remains at very low levels.

The increasing number of spotless days heralds the coming of the solar minimum expected in 2019/2020. The decline in the number of sunspots is greater than expected. This could be the deepest solar minimum in more than a century. This phase of the solar cycle brings increased numbers of cosmic rays to the Earth, an increased frequency of "pink" aurorae and a slight dimming of the Sun of approximately 0.1% in terms of the total solar irradiance. A new satellite has been launched, TSIS-1, which will monitor the Sun over the next five years covering the whole of the next solar minimum. Cooling and contraction of the Earth's upper atmosphere in response to the changes on the Sun due to the solar minimum also delayed the orbital decay of satellites such as the Chinese space station, Tiangong 1, which returned to Earth on April 2nd 2018 at 00:16 UTC. The Sun's magnetic field and solar winds provides some protection for the Earth from cosmic rays. A recent paper in the journal Space Weather claims that this solar minimum could see a rise in the number of cosmic rays reaching the Earth by as much as 30% due to the weakening magnetic field of the Sun and reduced levels of solar winds. This could mean an increased risk of radiation exposure for travellers on commercial airlines and possible changes to the climate.

NASA reported that a reversal of the Sun's magnetic field took place at the start of 2014 indicating that the maximum of solar cycle 24 had been reached. A plot of sunspot numbers, both observed and predicted versus time indicates that this solar maximum is more complex than had been previously predicted. The maximum is double-peaked in a similar manner to that of the previous maximum of 2001/2002. The individual peaks occurred in 2011 and 2014 with the latter being the larger of the two. However, sunspot numbers are significantly down on the predictions made for this maximum — indeed solar cycle 24 may be the weakest in the last 100 years or so i.e. since solar cycle 14. Assuming the start of 2014 was the beginning of the post maximum phase of solar cycle 24, we are now well into the decreasing phase of activity where individual energetic events can spawn some of the most powerful flares and coronal mass ejections of the cycle. The so-called Carrington event of 1859 is a good example of just what might be expected from this type of violent outburst. The next solar minimum, characterized by periods of many days without sunspots and flare activity, may occur in 2019 or 2020. It is likely to be a deep minimum with long periods without much sunspot or flare activity. Space weather will be dominated by solar winds and cosmic rays rather than sunspots and solar flares.

The latest information on solar activity can be found at SpaceWeather.com and at the Space Weather Prediction Center Space Weather Enthusiasts Dashboard.

If an auroral display is possible or likely, warnings can be received from AuroraWatch UK. More UK-focused geomagnetic data can be found at the British Geological Survey web site.


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Starfish imageThe Moon


The sequence of Moon phases for this month and their designations are shown in the following animation:

Continuous Moon Phase animation
  Moon phases for June 2018 are as follows:
Last Quarter symbol Last Quarter Wednesday June 6th at 19:32 BST
New Moon symbol New Moon Wednesday June 13th at 20:43 BST
Lunation 1181
First Quarter symbol First Quarter Wednesday June 20th at 11:51 BST
Full Moon symbol Full Moon Thursday June 28th at 05:53 BST

The Moon is at apogee (furthest from the Earth) on Saturday June 2nd at 17:35 BST when it is 405,317km from the Earth. It is at perigee (closest to the Earth) on Friday June 15th at 00:53 BST when it is 359,503km from the Earth. It is again at apogee on Saturday June 30th at 03:43 BST when it is 406,061km from the Earth.

Please follow the New Moon link above to find out more about our Crescent Moon Watch program which involves making sighting of the new crescent moon as early as possible after the instant of New Moon.

If you want to know what the Moon looks like now, try this USNO page generated by our colleagues in the Astronomical Applications Department at the US Naval Observatory in Washington.


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Starfish imageEclipses


Partial eclipse of the Sun There are five eclipses in 2018, two are total eclipses of the Moon and the remaining three are partial eclipses of the Sun. One total eclipse of the Moon is visible in the United Kingdom, namely that of 2018 July 27th. One partial eclipse of the Sun is also visible from the northernmost parts of the United Kingdom on 2018 August 11th.

A total eclipse of the Moon occurred on Wednesday January 31st 2018. It was visible in its entirety from Alaska, western Canada, the Hawaiian Islands, western Polynesia, Melanesia, Micronesia, most of Australia, New Zealand, eastern Indonesia, the Philippines, eastern China, Japan and eastern Siberia. Western parts of the United States, western China and India also saw the total phase of the eclipse. The eclipse ended just before moonrise in the United Kingdom so it was not visible in Taunton. Photographs of this eclipse taken around the end of totality show the effect of atmospheric scattering (left-hand image – red colouration) and ozone in the Earth's stratosphere (right-hand image – turquoise colouration).

A partial eclipse of the Sun occurred on Thursday February 15th 2018. It was visible in its entirety from most of Antarctica except parts of eastern Antarctica including Enderby Land, American Highland and Wilkes Land, and the southern part of South America including Argentina and the southern half of Chile. This eclipse was not visible from the United Kingdom.

A partial eclipse of the Sun will occur on Friday July 13th 2018. It will be visible from the easternmost part of Wilkes Land in Antarctica, the southern tip of New Zealand and the southernmost parts of South Australia and Tasmania. This eclipse is not visible from the United Kingdom.

A total eclipse of the Moon will occur on Friday July 27th 2018. It will be visible in its entirety from the Indian Ocean region, westernmost China, India, the Middle East, central Asia, Turkey and the eastern half of Africa. Most of Australia, the Philippines, Indonesia, most of China, western Africa and most of Europe will see the total phase of the eclipse. Some of the total phase of the eclipse is visible from the United Kingdom as the Moon rises during the umbral part of the eclipse. In Taunton, the Moon rises at 21:00 BST, approximately halfway between the start of the total phase at 20:30 BST and the middle of the total phase at 21:22 BST. The Moon will rise in a totally-eclipsed state and we will see about three quarters of the total phase of the eclipse.

A partial eclipse of the Sun will occur on Saturday August 11th 2018. It will be visible in its entirety from north-easternmost parts of Canada, Greenland, Iceland, northern Scotland, Scandinavia except Denmark, most of Russia except the south-western and eastern parts, and central Asia. In the United Kingdom, this eclipse is visible from the northernmost parts of Scotland, the Orkney Islands and the Shetland Islands as a very small partial eclipse with an obscuration of less than 1.8%. The eclipse will last 30 to 40 minutes with maximum obscuration occurring at around 9:49 BST. This eclipse will not be visible in Taunton.

Further information on all the eclipses in 2018 can be found on the Eclipses Online web pages. This web site provides information on both solar and lunar eclipses in the period from 1501 CE to 2100 CE. Global circumstances of both solar and lunar eclipses are provided as well as local circumstances of the solar eclipses based on a gazetteer of approximately 1500 locations worldwide. Eclipses for next year, 2019, are also available.


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Starfish imageThe Planets


Planets visible with the naked eye ...

Mercury image

Mercury reaches superior conjunction on Wednesday June 6th and re-emerges into the evening twilight sky in the middle of the month. It sets in the north-western sky less than an hour after sunset. Mercury fades from magnitude −1.1 at the middle of the month to magnitude −0.1 at the end of June. It lies 5° south of Pollux on Monday June 25th.


Venus image

Venus remains prominent in evening twilight sky during June. It sets in the late evening shortly before midnight in the north-western sky, more than two hours after sunset. Venus brightens somewhat from magnitude −3.9 to −4.1 by the end of the month. It lies 5° south of Pollux on Saturday June 9th and 2° north of the waxing crescent moon on Saturday June 16th.


Mars image

Mars continues to move south in the sky in the western part of the constellation of Capricornus. It starts its retrograde loop on Thursday June 28th, moving westwards for the next two months. Mars rises shortly after midnight in the south-eastern part of the sky. It brightens noticeably from magnitude −1.2 at the start of the month to −2.2 at the end of June. Mars will become the fifth brightest object in the sky after the Sun, Moon, Venus and Jupiter from June 10th through to mid-September. It will outshine the brightest star in the sky, Sirius, and its red colouration should be unmistakable during the second half of the night. Mars lies 3° south of the waning gibbous moon on Sunday June 3rd.


Jupiter image

Jupiter rises about four hours before sunset in the east south-eastern part of the sky. It is moving in a retrograde (westwards relative to the stars) manner through the western part of the constellation of Libra after passing opposition on Wednesday May 9th. Jupiter will remain in this constellation for much of 2018. It brightens somewhat from magnitude −2.5 at the start of June to −2.3 at the end of the month. Jupiter lies 4° south of the waxing gibbous moon on Saturday June 23rd.


Saturn image

Saturn rises in the south-eastern sky about two hours before midnight. It reaches opposition on Wednesday June 27th and lies in the constellation of Sagittarius where it will remain for the remainder of 2018. Saturn brightens somewhat from +0.2 at the start of the month to +0.0 at the end of June. It lies 1.6° south of the full moon on Friday June 1st and 1.8° south of the full moon on Thursday June 28th.


Planets visible with Binoculars ...

Uranus image

Uranus is visible in the morning twilight sky for observers with binoculars. It rises in the east north-eastern sky about two to three hours after midnight in the constellation of Aries, approximately 3.6° north east of the 4th magnitude star Omicron Piscium. Uranus is a blue-green object, having a magnitude of +5.9 for most of June and then brightening slightly to +5.8 at the end of the month. This planet can also be glimpsed with the naked-eye under optimum conditions.


Neptune image

Neptune is visible in the morning twilight sky for observers with a small telescope. It rises in the eastern sky about an hour or so after midnight. Neptune lies in the constellation of Aquarius approximately 4.7° to the east of the 4th magnitude star Lambda Aquarii. It starts its retrograde loop on Tuesday June 19th. It is a bluish object whose magnitude remains at +7.9 for the whole of June. It can be visible with good binoculars under optimum conditions. However, please note, that it can be difficult to distinguish Neptune from other stellar objects of a similar magnitude.


... & Telescopes!

Pluto image

Pluto lies in the north-eastern part of the constellation of Sagittarius and is visible in the south-eastern sky having risen an hour or so before midnight. Strictly speaking, this is a dwarf planet as it was demoted from the ranks of the "bona-fide" planets in 2006. I have to confess that I was one of those astronomers that voted for its demotion at the International Astronomical Union General Assembly in Prague! At magnitude +14.5, you will need a much more serious telescope to find this remote member of the Solar System.



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Starfish imageMeteor Showers


Perseid meteors in 2010 There are two meteor showers active during June. The principal shower is the Arietids and the other is the much weaker June Boötids. The Arietids are a daylight shower active from Monday May 14th to Sunday June 24th, peaking on Thursday June 7th with a zenithal hourly rate of around 30-60. However, the only slim chance of making visual observations of these meteors is to look very low in the east-northeastern sky during nautical twilight at the end of the first week of June. Very difficult observing circumstances are exacerbated by the presence of a last quarter moon. The origin of the Arietid meteor shower is uncertain. One suggestion is that they are debris from the sungrazing asteroid 1566 Icarus, another is that they are connected with the short-period comet 96P/Machholz.

The June Boötids are active from Friday June 22nd through to Monday July 2nd peaking on Wednesday June 27th. The radiant is visible all night long but the presence of a full moon at the peak of the shower will affect the useful observing time for these meteors. The hourly rate is extremely variable, perhaps fewer than 10 meteors per hour occasionally peaking up to 100, but the meteors can be quite bright. This shower occurs when the Earth crosses the orbit of the short-period sungrazing comet 7P/Pons-Winnecke.

No other significant meteor showers visible from our latitudes are active this month. Further information on these and other meteor showers occurring during 2018 can be found at the International Meteor Organization and their 2018 Meteor Shower Calendar.

It is worth noting that bright sporadic meteors and fireballs are possible at any time e.g. the fireball observed over many parts of England and Scotland on Saturday March 3rd 2012 at 21:40 GMT. Larger events, known as bolides, are rarer. Typically, this is a very bright fireball reaching an apparent magnitude of −14 or so, perhaps three times as bright as a full moon. Even rarer are the superbolides, events with apparent magnitudes of −17 or so, around 50 times brighter than the full moon. A recent example of a superbolide was the Chelyabinsk meteor of 2013 February 15th at 03:20 UTC which may have been a 20-metre diameter near-Earth asteroid.

Another loosely-related phenomenon is the re-entry of space debris from space vehicles and satellites whose orbits are decaying to the point where they burn up in the Earth's atmosphere. A couple of well-reported examples of this occurred at around 23:00 BST on Friday September 21st 2012 as well as the return of the GOCE satellite just after midnight on Tuesday November 12th 2013.

News ...

On Saturday June 2nd, a small asteroid was discovered near the orbit of the Moon by the Catalina Sky Survey based in Arizona. Designated 2018 LA, it hit the Earth a few hours later travelling at 17km/s (38,000mph). It exploded over Botswana at 6:44 p.m local time. A video of the explosion was taken from a farm between Ottosdal and Harteebeesfontein in north-western South Africa. The explosion was also detected by infra-sound equipment in South Africa used by the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. Analysis of the signals suggest that the explosion was in the 0.3-0.5 kiloton range and was generated by an object around 2 metres in diameter. 2018 LA is one of three boulder-sized impactors that have been detected burning up in the Earth's atmosphere in the last ten years; the others were 2008 TC3 which burned up over northern Sudan on October 7th 2008 and 2014 AA which burned up over the Atlantic Ocean on January 1st 2014. In each case, the warning was less than one day. Larger objects can be seen at greater distances and identified with (hopefully!) more warning.


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Starfish imageComets


Comet McNaught - January 2007There are a number of comets around the sky at the moment. However, most of them require telescopic assistance to see them and some may be too far south in the sky to be seen by observers based in the United Kingdom. Here is a brief summary of the comets that may be accessible to observers with binoculars or small telescopes in the northern hemisphere.

Comet C/2016 M1 PANSTARRS may attain eighth magnitude in late July before reaching perihelion on Friday August 10th. However, during this month, it will be visible low in the southern morning twilight sky in the constellation of Sagittarius, where it will remain for the first half of June. It then moves south beyond the reach of UK observers into the constellation of Corona Australis for a little over a week, after which it spends a couple of days in Scorpius before ending the month in the southern constellation of Ara. The comet should brighten slowly from magnitude +9.4 at the start of the month to +9.0 at the end of June.


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Starfish imageNoctilucent Clouds


Noctilucent Cloud Strictly speaking, this phenomenon is an atmospheric one rather than a truly astronomical one. Nonetheless, living in the United Kingdom, we are well placed to see this unusual spectacle during the shorter nights of the summer months, particularly in June and July.

These tenuous cloud-like structures are composed of ice-coated particles at an altitude of around 80km in the mesosphere, approximately four times higher than the limiting altitude of cirrus cloud. Created by water vapour freezing around meteor smoke in the upper atmosphere, their altitude means that they appear silvery-blue in colour against the darker twilight sky when the Sun lies between 6° and 16° below the horizon.

Noctilucent or "night shining" Cloud is normally seen between 10° and 20° above the northern horizon exhibiting a range of forms — perhaps the most common is the "herring-bone" pattern. Normal visibility limits are mid-May to mid-August, peaking around the time of the Summer Solstice. More information, including the facility to report your sightings, can be found at the Noctilucent Cloud Observers' Homepage.

A word of warning; displays are unpredictable and more frequently seen from the northern half of the United Kingdom. Nevertheless, observations have been submitted by observers living in this locality e.g. from Exeter and Castle Cary.

Maps constructed from AIM satellite imagery showing the current positions of Noctilucent Clouds have been restored. They can be found here.

A particularly nice animation of this phenomenon taken before dawn on June 3rd 2013 by The Sky at Night's Pete Lawrence is well worth a look. A photograph demonstrating that these clouds can be seen from southern parts of the United Kingdom was taken by D. Tate in Castle Cary in the early hours of June 10th 2013.

News ...

[4th June 2018] The northern noctilucent cloud season has started in earnest. On the evening of Sunday June 3rd displays were seen across northern Europe including Northern Ireland, Scotland, Norway and Denmark although sporadic observations have been reported since May 23rd. The AIM satellite, which is monitoring polar mesospheric clouds (a more technical name for noctilucent clouds), has shown that over the last five days, the noctilucent cloud cover over the north polar regions has risen by a factor of 100.

[20th June 2018] A fine display of noctilucent cloud was seen from Scotland on the night of June 19th/20th 2018. This image was taken from the Isle of Lewis at approximately 01:00 BST. The display was notable not only because of its intensity but its fine rippling structure as well.


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Starfish imageInternational Space Station


NASA International Space Station photo If you want to look for the International Space Station (ISS) as it passes over Taunton, please have a look at this page on the Heavens Above web site. The ISS is at least as bright as a first magnitude star and can approach the brightness of Venus. Similarly, if you want to look for the Chinese space station, Tiangong-1, you are too late! Tiangong-1 re-entered the Earth's atmosphere in an "uncontrolled manner" on April 2nd 2018 at 00:16 UTC over an uninhabited part of the central Pacific Ocean at longitude 164.3° west and 13.6° south after the loss of a telemetry link in 2016. Information for Tiangong-2, the sole remaining Chinese space station orbiting the Earth, can be found on this page. Tiangong-2 is significantly fainter than the ISS, normally as bright as a third or fourth magnitude star. Predictions for other satellites may also be obtained from the Heavens Above web site.

Another satellite-related phenomena to look out for are the so-called "Iridium flares". These bright flashes of sunlight reflecting off the Iridium series of communication satellites can be seen at night and also occasionally during the daytime if they are bright enough. Predictions for the next seven nights are available.


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Starfish imageAurorae


Ovation auroral prediction for the northern hemisphere

The above image is a 30 minute forecast of the location and probability of auroral activity based loosely on a model developed at Johns Hopkins' Applied Physics Laboratory known as the Ovation Aurora Forecast model. It provides estimates of the energy per unit area on the Earth's atmosphere from observations of the solar wind and interplanetary magnetic field made by the Advanced Composition Explorer satellite in conjunction with empirical relationships derived from the Defense Meteorological Satellite Program. It shows where the aurora is most likely to be seen and how bright it is likely to be. The model generates a global estimate of power, called the Hemispheric Power, deposited into the atmosphere in gigawatts (GW). For powers of less than 20GW, little or no aurora may be visible. For powers of 20-50GW, you may need to be relatively close to the aurora to see it. For values above 50GW, the aurora should be easily observable, active and mobile. For values above 100GW, this is considered to be a significant storm where the aurora may be visible from hundreds of miles away. The current prediction is downloaded when you load this page. If you want to download the latest model, simply reload this page or hit F5. If you want to see the full-sized map, please click on the above image.

If an auroral display is possible or likely, warnings can be received from AuroraWatch UK. More UK-focused geomagnetic data can be found at the British Geological Survey web site.


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Starfish imageSky chart for mid-June at 22:00 BST for Taunton


Sky chart for mid-June 2018 from Taunton at 22:00 BST

The above sky chart, generated from the Heavens-Above.com web site, shows what the night sky looks like at 22:00 BST on Friday June 15th 2018 from Taunton. The night sky will look the same an hour later at 23:00 BST at the beginning of the month and an hour earlier at 21:00 BST at the end of the month. If you want to generate your own star chart for Taunton for another date and/or time please follow this link


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Rise/set times (BST) for the Sun & Moon for Taunton


In June 2018, the amount of daylight (measured from sunrise to sunset) increases from 16 hours 15 minutes at the start of the month to 16 hours and 33 minutes at the Summer Solstice and then decreases to 16 hours 29 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 494 hours 5 minutes.

start and end times of civil, nautical and astronomical twilights.

June 2018
Date &
Weekday
Rise/Set timesDay
Length
SunMoon
RiseSetRiseSet
h mh mh mh mh m
01Fri05:0321:1823:4107:2616:15
02Sat05:0321:19** **08:1816:16
03Sun05:0221:2000:2209:1416:18
04Mon05:0121:2100:5610:1516:20
05Tue05:0121:2201:2611:1816:21
06Wed05:0021:2201:5212:2316:22
07Thu05:0021:2302:1513:3016:23
08Fri04:5921:2402:3714:4016:25
09Sat04:5921:2503:0015:5116:26
10Sun04:5821:2603:2317:0616:28
11Mon04:5821:2603:5018:2316:28
12Tue04:5821:2704:2119:4116:29
13Wed04:5821:2805:0020:5816:30
14Thu04:5721:2805:4922:0716:31
15Fri04:5721:2906:4923:0616:32
16Sat04:5721:2907:5823:5416:32
17Sun04:5721:3009:15** **16:33
18Mon04:5721:3010:3300:3316:33
19Tue04:5721:3011:5001:0416:33
20Wed04:5721:3013:0501:3116:33
21Thu04:5821:3114:1801:5416:33
22Fri04:5821:3115:2802:1716:33
23Sat04:5821:3116:3702:4016:33
24Sun04:5821:3117:4503:0416:33
25Mon04:5921:3118:5003:3216:32
26Tue04:5921:3119:5104:0316:32
27Wed05:0021:3120:4804:3916:31
28Thu05:0021:3121:3805:2216:31
29Fri05:0121:3122:2206:1116:30
30Sat05:0121:3022:5807:0616:29
** ** No phenomenon that day
PLEASE NOTE: These times are in Greenwich Mean Time (GMT) except between 01:00 GMT on March 25th and 01:00 GMT on October 28th when the times are in BST (British Summer Time) which is one hour in advance of GMT.

Useful area for table of rise/set times The timings in the table above should be accurate to within 1-2 minutes inside the red circle superimposed on the map shown on the left.

Rising and setting times for the Sun, Moon and planets and times of twilights for other locations can be obtained from HMNAO's Websurf web pages.

The actual times at which the Sun will just appear, or disappear, will depend on the difference of the altitudes of the observer and the local horizon and the actual refraction, which depends on the meteorological conditions along the light path. Differences of a minute or so from the tabulated times are to be expected.

For the drivers amongst you, the "Hours of Darkness", as defined by the Road Vehicle Lighting Regulations (1989), start half an hour after sunset and end half an hour before the following sunrise. Headlights should be used during the Hours of Darkness and sidelights in the half hour periods after sunset and before sunrise. These timings can also be obtained from HMNAO's Websurf web pages using the Rise, Set and Twilight Times option.

For the VFR (Visual Flight Rules) pilots amongst you, night, according to Statutory Instrument 2009 No. 3015, Civil Aviation, The Air Navigation Order 2009, Part 33 (Interpretation), Article 255(1), means "the time from half an hour after sunset until half an hour before sunrise (both times inclusive), sunset and sunrise being determined at surface level". In other words, the night time period starts at the beginning of the Hours of Darkness and finishes at the end of the Hours of Darkness.


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Last modified: Friday, 22 June 2018 at 08:55:34 BST