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:
Additional information on the phases of the Moon, the seasons, summer times, eclipses, chronological cycles and eras, religious calendars, the civil calendar and holiday dates in the United Kingdom can be found in HMNAO's Astronomical and Calendarial Sheet No. 107 for 2020. This is a pdf document for which a document reader can be downloaded by clicking on the Adobe Reader icon above.
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 Sunday, 2020 May 31 at 18:21:55 BST.
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.
The Sun has now been devoid of active regions for the past twenty nine days. The total number of spotless days for 2020 has risen to one hundred and twenty, or 79% of the year so far. The Sun has not displayed so few sunspots since 1913 and this minimum may well be the deepest of the Space Age. Solar winds are currently blowing with velocities of around 400 km/s and the planetary Kp geomagnetic activity index is likely to peak at 3 (quiet) today. Earth orbiting satellites have detected a flurry of mostly B-class solar flares in the last day or so over the north-eastern limb of the Sun. Indeed, one of these was a M1-class solar flare which was the strongest in nearly three years. This activity is connected to the magnetic canopy of a small sunspot with an extensive plage region surrounding it which may rotate into view within the next couple of days. There are no coronal holes on the visible disk of the Sun. 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 upcoming 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 provide 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 declining 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 on September 1st–2nd 1859 during Solar Cycle 10 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, is likely to occur between July 2019 and September 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 flare activity. The next solar maximum is expected to occur between 2023 and 2026. Solar cycle 25 is likely to be similar to solar cycle 24 which means another weak maximum and a long, deep minimum.
The sequence of Moon phases for this month and their designations are shown in the following animation:
|Moon phases for May 2020 are as follows:|
|Full Moon||—||Thursday May 7th at 11:45 BST
"Milk Moon" / Supermoon
|Last Quarter||—||Thursday May 14th at 15:03 BST|
|New Moon||—||Friday May 22nd at 18:39 BST
|First Quarter||—||Saturday May 30th at 04:30 BST|
The Moon is at perigee (i.e. closest to the Earth) on Wednesday May 6th at 04:03 BST when it is 359,654 km from the Earth. It is at apogee (i.e. furthest from the Earth) on Monday May 18th at 08:45 BST when it is 405,583 km 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.
The term 'Supermoon' was coined in 1979 by astrologer Richard Nolle. He defined it as "a new or full moon which occurs with the moon at or near (within 90 percent of) its closest approach to Earth in a given orbit", without explaining why the 90 percent figure was chosen. As the Moon's orbit is elliptical, not circular, there is a point in its orbit where it is closest to the Earth (perigee) and another one where it is furthest away from the Earth (apogee) and these perigee and apogee distances change somewhat from one orbit to another. In the period between 1850 and 2050, perigee distances for the Moon range from 356,375 km to 370,355 km while apogee distances range from 404,055 km to 406,710 km. Using Nolle's criterion, on average, a full moon occurring within 367,607 km of the Earth will be a supermoon.
The closest full moons occur on average in cycles of just over a year as 14 lunar months or lunations is only 2.7 hours longer than the time taken for 15 returns to perigee. The full moon of 2020 February 9th takes place at a distance of 362,477 km, nearly 37 hours before perigee. The next full moon of March 9th takes place at a distance of 357,400 km, less than 13 hours before perigee. The full moon on April 8th takes place at a distance of 357,030 km, just over 8 hours after perigee. The full moon on May 7th takes place at a distance of 361,183 km, less than 32 hours before perigee. The February and May full moons are marginal supermoons and, by some, may not be classed as supermoons. The full moons within this four month period of 2020 all take place at distances of less than 362,500 km from the Earth. We might say that the supermoon of April 8th is more super than the other three supermoons as it takes place at a distance of only 357,035 km from the Earth. However, it does not make the list of the fifteen closest full moons in the interval 1850–2050 given below.
|The Fifteen Closest Full Moons: 1850–2050|
The four closest full moons in the 21st century will take place on 2034 November 25th at 22:32 UT at a distance of 356,446 km, 2052 December 6th at 07:18 UT at a distance of 356,426 km, 2070 December 17th at 16:05 UT at a distance of 356,463 km and 2098 January 17th at 10:36 UT at a distance of 356,461 km. Perhaps these will be known as 'Ultimoons'!
Many media articles will mention that the Moon will be 14% bigger and 30% brighter than when the full moon occurs furthest from the Earth or 7% bigger and 15% brighter than average. A nice illustration of this can be seen on the Astronomy Picture of the Day site. As a result of these differences, you might expect to see a significantly bigger and brighter Moon but this is not the case. The transition between an apogee full moon and a perigee full moon takes place over seven lunar cycles so the apparent changes in size from one full moon to the next are only perhaps 2% in apparent size and 3% in apparent brightness. These changes are more difficult to detect. Indeed, discerning changes in the size of the Moon is even more difficult to perceive when the Moon is close to the horizon due to the so-called 'Moon Illusion'. On a given night, the rising or setting Moon will appear larger than when it is high in sky. There is no proper explanation for this perceived difference but it may be related to the presence of perceptual cues for the eye near the horizon which are missing for an object much higher in the sky.
Is the supermoon just another piece of media hype? Have you also noticed the increasing use of the term 'Micromoon' for the smallest full moon in a given period of time? Neil de Grasse Tyson, the director of the Hayden Planetarium in New York, has suggested that supermoons are indeed over-hyped. "I don't know who first called it a Supermoon" he told StarTalk radio. "I don't know, but if you have a 16-inch pizza, would you call that a super pizza compared with a 15-inch pizza?". Enough said ...
There are six eclipses visible during 2020, four penumbral eclipses of the Moon and one annular and one total eclipse of the Sun. Parts of three of the penumbral eclipses of the Moon are visible from the United Kingdom, only one is visible in its entirety. Neither of the solar eclipse are visible from the United Kingdom.
A penumbral eclipse of the Moon occurred on Friday January 10th 2020. It was visible in its entirety from northern Alaska, Asia, the Philippines, Indonesia, western Australia, the Middle East, Madagascar, Africa except eastern parts, Europe including the United Kingdom, Iceland and most of Greenland. Parts of the eclipse were visible from north-western parts of North America, most of Australia, eastern parts of Africa and north-eastern parts of Canada. This was a deep penumbral eclipse with a magnitude of 0.921, making it somewhat easier to discern. From Taunton, the whole eclipse was visible starting about an hour after moonrise at 17:06 UT and ending at 21:14 UT.
A penumbral eclipse of the Moon occurs on Friday June 5th 2020. It is visible in its entirety from most of Australia except the north-eastern part, the Philippines, Indonesia, south-east Asia, most of China except the north-eastern part, central Asia, India, the Middle East, Madagascar and Africa except the north-west part. Parts of the eclipse are visible from New Zealand, Japan, northern Asia, Europe including the United Kingdom, north-western Africa and easternmost parts of South America. This is a modest penumbral eclipse with a magnitude of 0.593, making it difficult to discern. From Taunton, the eclipse starts at moonrise at 21:12 BST and ends at 22:07 BST.
An annular eclipse of the Sun occurs on Sunday June 21st 2020. It is visible in its entirety from most of the eastern half of Africa, the northern half of Madagascar, south-east Europe, most of Asia except the northernmost part, westernmost parts of Micronesia and Melanesia, Papua New Guinea and northernmost parts of Australia. The path of annularity begins over the north-eastern part of the Republic of the Congo and crosses the north-western part of the Democratic Republic of Congo, the south-eastern tip of the Central African Republic, South Sudan, northern Ethiopia, central Eritrea, Yemen, the south-eastern tip of Saudi Arabia, north-eastern Oman, Pakistan, the northernmost part of India, Tibet, southern China, Taiwan and ends south-east of Guam in the Northern Mariana Islands. The eclipse is not visible from the United Kingdom.
A penumbral eclipse of the Moon occurs on Sunday July 5th 2020. It is visible in its entirety from westernmost parts of Africa and the Americas with the exception of north-western parts of North America. Parts of the eclipse are visible from Madagascar, most of Africa, western Europe including the United Kingdom, the southernmost part of Greenland and north-western parts of the United States, central Canada, eastern Polynesia and New Zealand. From Taunton, the shallow penumbral eclipse starts at 04:04 BST and ends at moonset at 05:01 BST. It will be a difficult eclipse to detect with the naked eye.
A penumbral eclipse of the Moon occurs on Monday November 30th 2020. It is visible in its entirety from Greenland, North America, Polynesia, the North Island of New Zealand, northern Japan and Siberia. Parts of the eclipse are visible from Scandinavia, the United Kingdom, the Caribbean region, South America, the South Island of New Zealand, Australia, south east Asia and central Asia. From Taunton, the reasonably deep penumbral eclipse starts at 07:30 UT and ends at moonset at 07:48 UT. The depth of the eclipse will make it easier to discern.
A total eclipse of the Sun occurs on Monday December 14th 2020. It is visible in its entirety from the south-eastern part of the Pacific basin including French Polynesia, most of South America except the northern part, parts of Antarctica, the South Atlantic Ocean and the south-western part of Africa. The path of totality begins over the north-eastern part of French Polynesia and passes over the south-eastern Pacific Ocean and then crosses the central part of Chile and Argentina, passing over the South Atlantic Ocean and ends just off the coast of central Namibia. The eclipse is not visible from the United Kingdom.
Further information on all the eclipses in 2020 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, 2021, are also available.
Mercury reaches superior conjunction with the Sun on Monday May 4th and is too close to the Sun to be observed. It reappears in the western evening twilight sky in mid-May when it is magnitude −1.1. Mercury then fades to 0.0 by the end of May. It lies 7° north of Aldebaran on Sunday May 17th and 0.9° south of Venus on Friday May 22nd.
Venus gets progressively lower in the sky during the month as it moves towards inferior conjunction on Wednesday June 3rd. It gets too close to the Sun to observe in the last week of May. Venus is still unmistakable in the north-western evening twilight sky although it fades significantly from magnitude −4.7 at the start of the month to magnitude −4.1 at the end of May. It lies 0.9° north of Mercury on Friday May 22nd and 4° north of the waxing crescent Moon on Sunday May 24th.
Mars is visible in the east south-eastern morning twilight sky, rising two to three hours before the Sun and setting just after noon. It spends the first week of May in the constellation of Capricornus and then moves into Aquarius for the rest of May. Mars brightens noticeably from magnitude +0.4 at the start of the month to 0.0 at the end of May. It lies 3° north of the waning crescent moon on Friday May 15th.
Jupiter is visible in the south-eastern morning twilight sky rising between two and three hours before the Sun and setting in the mid-morning. It lies in the constellation of Sagittarius until late December. Jupiter brightens somewhat from magnitude −2.3 to −2.6 during May. It lies 2° north of the waning gibbous moon on Tuesday May 12th. Jupiter and Saturn lie less than 5° apart in the south-eastern morning twilight sky for the whole of May.
Saturn is visible in the south-eastern morning twilight sky rising between two and three hours before the Sun and setting in the late morning. It lies in the constellation of Capricornus for the whole of May. Saturn brightens somewhat from magnitude +0.6 to magnitude +0.4 during May. It lies 3.0° north of the waning gibbous moon on Tuesday May 12th. Saturn and Jupiter lie less than 5° apart in the south-eastern morning twilight sky for the whole of May.
Uranus disappeared from our evening skies in early April reaching conjunction with the Sun on Sunday April 26th. and reappears in the morning twilight sky in mid-May. It is a blue-green object of magnitude +5.9 which lies in the south-western part of the constellation of Aries where it remains for the rest of the year. Uranus is approximately 9.8° north east of the fourth magnitude star Omicron Piscium. This planet can also be glimpsed with the naked eye under optimum conditions.
Neptune rises about two hours before the Sun and lies in the north-eastern part of the constellation of Aquarius where it will remain for the rest of the year. It is approximately 8.8° to the north east of the third magnitude star Lambda Aquarii. Neptune is a bluish object of magnitude +7.9 for the whole of May. It can be visible with good binoculars under optimum conditions although it can also be difficult to distinguish Neptune from other stellar objects of a similar magnitude.
Pluto rises about four hours before the Sun in the south-eastern morning twilight sky. It lies in the north-eastern part of the constellation of Sagittarius about 2.3° to the south west of Jupiter in mid-May. Strictly speaking, this is a dwarf planet which was demoted from the ranks of the 'bona-fide' planets at the International Astronomical Union General Assembly in Prague in 2006. At magnitude +14.4, you will need a much larger telescope to find this remote member of the Solar System.
The Eta Aquariids are active between Sunday April 19th and Thursday May 28th, peaking on Tuesday May 5th at around 22:00 BST. They are best seen from tropical and southern latitudes in a short window as the radiant rises above the eastern horizon in the pre-dawn sky at the end of the first week of May. It has to be said that the peak of this shower is more of an extended plateau of activity lasting several days centred on the maximum. This shower exhibits a variable rate of around 50 meteors per hour, occasionally peaking as high as 85 meteors per hour. The shower is affected by moonlight this year as the nearly full moon is visible throughout the night. The shower is also likely to be affected by the increasing morning twilight glow. The meteors are often swift and bright with long, persistent trains. This shower is loosely connected with Comet 1P/Halley, having separated from the comet hundreds of years ago.
No other significant meteor showers visible from our latitudes are active this month. Further information on these and other meteor showers occurring during 2020 can be found at the International Meteor Organization and their 2020 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.
There 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.
C/2017 T2 (PANSTARRS) starts the month as a magnitude 8.6 object visible with a small telescope in the constellation of Camelopardalis before crossing over into the neighbouring constellation of Ursa Major for the last two weeks of May. It is circumpolar so it is visible throughout the night but it is highest in the sky in the early part of the night. It should reach perihelion on Monday May 4th 2020 by which time it may become a magnitude 8.3 object.
C/2019 Y1 (ATLAS) is visible with a small telescope at the start of the month in the constellation of Cepheus. After two days, it passes in to Camelopardalis for six days and then into Draco for the next four days. It then moves into Ursa Major for the remainder of the month. It is circumpolar so it is visible throughout the night but it is highest in the sky after evening twilight. This comet is a magnitude 8.2 object which is likely to fade by more than a magnitude during May having already passed perihelion in mid-March.
C/2019 Y4 (ATLAS) is visible with a small telescope high in the evening sky in the constellation of Camelopardalis for the first twelve days of May. It then moves into Perseus, for two weeks, ending the month in Taurus. After promising to be a bright naked-eye comet, C/2019 Y4 (ATLAS) has fragmented into several pieces and faded significantly. The question is, will the comet survive until it reaches perihelion at the end of May? During this month, it moves closer to the horizon making the observation window shorter as the month progresses. At the start of the month it is a 9th magnitude object. However, it could still brighten to around 8th magnitude if no further fragmentation occurs. This comet continues to surprise observers. In the last few days, one of the four main fragments has developed a tail of its own generating a comet within a comet.
This bright comet was discovered on Saturday March 25th this year using data from the Solar Wind Anisotropies Camera on the SOHO satellite by Australian astronomer Michael Mattiazzo. As of Saturday May 2nd, C/2020 F8 (SWAN) was a magnitude 4.7 object best visible from the southern hemisphere in the constellation of Cetus. During May, it passes through Pisces, Triangulum, and Perseus, ending the month in Auriga. It faded in the last few days to 6th magnitude but has recovered somewhat to magnitude 5.5. This comet is in a hyperbolic orbit, visiting the inner solar system for the first time from somewhere within the Oort cloud. It has a prominent tail as can be seen from this recent movie which is more than 8° in length. Unfortunately, from the northern hemisphere, it will only be visible with binoculars very low in the north-eastern morning twilight sky in the latter part of May. Indeed, the comet will lie in the constellation of Perseus after May 19th and then Auriga for the last two days of May after reaching perihelion on Wednesday May 27th at a distance of 0.43 au from the Sun.
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 80 km 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.
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.
The first noctilucent cloud display of the northern season was seen by the AIM satellite over the Arctic Ocean north of Siberia on May 17th and marks one of the earliest starts to the NLC season. The display was small and relatively weak but it should not be too long before stronger displays appear over northern parts of the United Kingdom. Another small display was reported by ground-based observers in Estonia, Finland and Latvia on May 23rd.
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.
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 might 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 press F5. If you want to see the full-sized map, please click on the above image.
The above sky chart, generated from the Heavens-Above.com web site, shows what the night sky looks like at 22:00 BST on Saturday May 16th 2020 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. Please click on the chart to see a full-sized sky chart image. If you want to generate your own star chart for Taunton for another date and/or time, please follow this link
In May 2020, the amount of daylight (measured from sunrise to sunset) increases from 14 hours 50 minutes at the start of the month to 16 hours 13 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 483 hours 12 minutes.
start and end times of civil, nautical and astronomical twilights.
|h m||h m||h m||h m||h m|
|** ** No phenomenon that day|
|PLEASE NOTE: These times are in Greenwich Mean Time (GMT) except between 01:00 GMT on March 29th and 01:00 GMT on October 25th when the times are in BST (British Summer Time) which is one hour in advance of GMT.|
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 using the Rise, Set and Twilight Times option.
The actual times at which the Sun will just appear, or disappear, will depend on the difference between 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 in 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.