Indholdsfortegnelse for May 2021 i BBC Sky at Night

As an island nation, the UK has almost 17,820km of mainland coastline (according to the Ordnance Survey), which rises to 31,370km when you include its hundreds of islands. When you consider its surface area that’s pretty high, and in fact the UK’s is the 12th longest coastline globally. Our seashore is also a region that has a special appeal to stargazers and astro imagers for many reasons, chief among them being big open views that extend unhindered low to the horizon. In this month’s issue, on page 28 Will Gater is your guide to observing from coastal settings, revealing expert tips on how to observe from public areas responsibly, and the objects that are brought out at their best by a sea view. Whatever your observing location, spring is a…

Ron Brecher Deep-sky observer “Globular clusters are among my favourite objects to view through the eyepiece and to image, which made it fun to write this article highlighting some of the most striking examples.” Ron picks the year’s best globulars, page 34 Charlotte Daniels Astrophotographer “DSLR cameras are a great option for astro imaging; get to know their features and settings and you can be capturing beautiful images of the night sky in no time”. Charlotte goes back to basics with DSLRs, page 60 Govert Schilling Astonomy journalist “Working on the Great Debate story made me realise the enormous progress astronomers have made in our understanding of the Universe in one century.” Govert introduces the key figures in 1920’s Great Debate, page 66…

Email your queries to scopedoctor@skyatnightmagazine.com I have a Meade ETX-125EC telescope that came with an SP26mm eyepiece, but I have since acquired three Meade series 5000 HD-60 eyepieces with 9, 12 and 18mm focal lengths. What types of target are each of the eyepieces best used for? CAROL BOLTON The Meade ETX-125EC is a Maksutov-Cassegrain so it has a relatively long focal length of 1,900mm, making it a good choice for lunar and planetary observations where high magnifications are required. With it, your 26mm, 18mm, 12mm and 9mm eyepieces will deliver magnifications of 73x, 105x, 158x and 211x respectively. Remember that higher magnification doesn’t always improve the close-up detail in celestial objects, but with good seeing conditions this scope should give some great views of the planets with the 12mm…

16-PAGE CENTRE PULLOUT EVENING ENCOUNTER View Venus near a thin crescent Moon TRAIL FINDER How to spot the peak of the Eta Aquariid meteor shower About the writers Astronomy expert Pete Lawrence is a skilled astro imager and a presenter on The Sky at Night monthly on BBC Four Steve Tonkin is a binocular observer. Find his tour of the best sights for both eyes on page 54 Also on view this month… ✦ Noctilucent cloud season begins ✦ The lunar ‘X’ and ‘V’ clair-obscur effects ✦ The year’s brightest and largest full Moon Red light friendly To preserve your night vision, this ‘Sky Guide’ can be read using a red light under dark skies Get the Sky Guide weekly For weekly updates on what to look out for in…

Universal time (UT) and British Summer Time (BST) Universal Time (UT) is the standard time used by astronomers around the world. British Summer Time (BST) is one hour ahead of UT RA (Right ascension) and dec. (declination) These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object is on the celestial ‘globe’ Family friendly Objects marked with this icon are perfect for showing to children Naked eye Allow 20 minutes for your eyes to become dark-adapted Photo opp Use a CCD, planetary camera or standard DSLR Binoculars 10x50 recommended Small/medium scope Reflector/SCT under 6 inches, refractor under 4 inches Large scope Reflector/SCT over 6 inches, refractor over 4 inches GETTING STARTED IN ASTRONOMY If you’re new to astronomy, you’ll find two essential reads on our…

KEY TO STAR CHARTS When to use this chart 1 May at 01:00 BST 15 May at 00:00 BST 31 May at 23:00 BST On other dates, stars will be in slightly different positions because of Earth’s orbital motion. Stars that cross the sky will set in the west four minutes earlier each night. How to use this chart 1. Hold the chart so the direction you’re facing is at the bottom. 2. The lower half of the chart shows the sky ahead of you. 3. The centre of the chart is the point directly over your head. Sunrise/sunset in May* Moonrise in May* Moonrise times 1 May 2021, 01:37 BST 5 May 2021, 04:08 BST 9 May 2021, 05:00 BST 13 May 2021, 06:04 BST 17 May 2021, 09:01…

1 IC 1396 First up is the visually difficult nebula, IC 1396. Occupying a roughly circular area in southern Cepheus, the orange variable star Erakis (Mu (µ) Cephei) sits on its north-northeast edge. IC 1396 stretches 2.5˚ south-southwest of this star. The nebula is visually difficult due to low surface brightness. It contains the open cluster Trumpler 37 and the lovely triple Struve 2816 (Y2816) at the region’s centre. A dark sky combined with a rich-field 150mm or larger scope will give the best results. Use a low power eyepiece and an OIII (oxygen) visual filter. □ SEEN IT 2 vdB 142 The object vdB 142 (IC 1396A) is a dark region within IC 1396. Double star Ʃ2813 sits centrally within vdB 142. A number of knots of brighter emission…

How China changed astronomy Jamie Carter reveals how China’s thirst for space knowledge traces back to ancient sky-lore Our constellations come from ancient Greek and Roman mythology. Many of the brightest stars we see - such as Betelgeuse (Alpha (α) Orionis), Deneb (Alpha (α) Cygni) and Algol (Beta (ᵦ) Persei) - were named in Arabic by Islamic astronomers. What we overlook when we gaze at the night sky is the incredible influence of Chinese astronomers. Everyone knows about the Chinese or Lunar New Year, which starts on the day after the first new Moon that falls between 21 January and 20 February (in the Gregorian calendar) and ends with the next full Moon. You may also know about the Chinese belief that solar eclipses occur when a dragon eats the…

How much do we know about the Universe? In theory, we know what the Universe is made of, that all matter-energy content is ‘normal’ matter, dark matter or dark energy. But ‘normal’ is only about four per cent of the total matter-energy content, and that includes us. Humans are not just abnormal because there is only one Earth, it’s because most of what we see is a tiny percentage of the Universe’s matter-energy content. The rest is dark matter and dark energy. What do we know about the Big Bang? People think of the Big Bang as like an explosion, but if it really was a thing, it’s a moment in time that happens everywhere. When the Universe was less than a second old, space-time expanded exponentially. Perhaps lots of…

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Seeing a fireball is special – but meteorites are magic. Beyond the rich scientific yield we get, they provide an unusually physical connection to the cosmos above. I became an astronomer because I love staring at the night sky and wondering what else might be there. To touch a meteorite gives me the same feeling. Of course, not all meteorites are equal. Talking to the scientists who are working on the Winchcombe meteorite for the TV show this month was brilliant, but I’ll never forget picking up a tiny vial with something that was in orbit about the Sun a couple of weeks before. It may have looked like a left over stock cube, but it will be a moment I’ll treasure for ever. Chris Lintott co-presentsThe Sky at Night…

Email us at inbox@skyatnightmagazine.com Tweet Jeff M @jeffnmark • Mar 17 M81 in Ursa Major. About 2.5 hrs of 3-minute exposures, using a @zwoasi 533MC camera @ IM_SKYWATCHER 200PDS 8” telescope, EQ6r mount, ZWO 224 guide camera, controlled with an AsiAir. @skyatnightmag @AstroHour321 #pixinsight A landmark aurora Thank you for your article ‘Chasing the Aurora’ by Tom Kerrs (March 2021 issue, page 28). This rekindled memories of a boyhood conversation on the aurora borealis with my grandfather, Frederick Walter Mann (1905-98), who encouraged my early interest in astronomy. He recalled seeing the dramatic aurora of 25 January 1938, one of the rare occasions a display was visible across the whole of Great Britain as far south as Cornwall. He saw it from Barton Hill, the highest point near Bury St…

Where I live in southern Canada, the cold, cloud and snow can make winter observing a challenge, but eventually the temperatures moderate, the clouds part and the snow melts. That’s when I get my 10- and 20-inch (250mm and 300mm) Dobsonian telescopes out to view my favourite eyepiece targets: globular clusters. The best-in-class globular clusters are located in the Southern Hemisphere, where specimens such as Omega (ω) Centauri and 47 Tucanae outshine any globular visible from mid-northern latitudes. However, since most readers of this article, like me, are located north of latitude 40˚ North, I’ve focused on targets that are easily visible from my locale. These spherical agglomerations of stars look good in any optics and, more than any other class of object, become more impressive with increasing aperture. ‘Globulars’,…

DON’T MISS JOVIAN EQUINOX BEST TIME TO SEE: 6, 14 and 29 May at specified times Jupiter reaches equinox on 2 May, a position where the geometric centre of the Sun’s disc appears to cross the equatorial plane of the planet. Compared to Earth, Jupiter’s axial tilt is quite small; 3.3˚ compared to our planet’s 23.4˚. For this reason, seasonal variations on Jupiter are relatively minor. Of more significance from our perspective, the four Galilean moons Io, Europa, Ganymede and Callisto, have orbits which are only slightly inclined to Jupiter’s equatorial plane. At those times away from an equinox, if the orbits of these moons were directly visible, from the Sun they would appear like narrow ellipses. Near to a solstice – a position where one of the planet’s poles…

Langrenus Type: Crater Size: 133km Longitude/Latitude: 61° E, 8.9° S Age: Between 1.1–3.2 billion years Best time to see: Three days after new Moon (14 May) or two days after full Moon (28 April and 27 May) Minimum equipment: 10x binoculars Langrenus is a prominent crater located near ‘ to the Moon’s eastern limb. As such it gets affected by lunar libration, a rocking and rolling effect caused by the Moon’s orbit. Being so close to the eastern limb, from Earth, Langrenus appears foreshortened into an ellipse. Although it stays visible throughout the libration cycle, the degree of ellipticity waxes and wanes according to where the crater appears relative to the limb. Langrenus marks the northern point of a trio of similar sized features, all located at a similar apparent…

DSLRs (digital single-lens reflex cameras) are brilliantly versatile astrophotography cameras, and for a wide range of reasons. They perform well for most types of target, including wide-field Milky Way shots, Moon images, and deep-sky objects like galaxies and nebulae. Great for beginners, they are easy to use and can be cheap to buy, depending on the model. Plus, there’s a secondhand market for entry level cameras. DSLRs have a digital sensor and reflex mirror that directs incoming light onto the viewfinder. You can attach different lenses to them and they are also more sensitive in low light, which is important. You can get started in DSLR astrophotography simply with the camera and a tripod, rather than jumping straight into guiding. The lenses available also provide the ability to shoot at…

1. Halley’s Comet: first recorded sighting On 30 March 239 BC a sighting of Halley’s Comet was recorded in the Shih Chi and Wen Hsien Thung Khao chronicles; in the 2,260 years since, every return has been recorded in China. 2. First reliable record of a solar eclipse The 4 June 2021 will mark 2,801 years since the first reliable record of a total solar eclipse was made by Chinese observers in 780 BC. (There are etched bones with illustrations that go back further.) 3. Earliest known observation of sunspots Official imperial records include a mention of 112 sightings of sunspots between 28 BC and AD 1638, but the earliest recorded observations go back to 364 BC by Chinese astronomer Gan De. 4. The oldest preserved star atlas Discovered in…

1 Pegasus Scops motorised off-axis guider Price £495 • Supplier Widescreen-Centre www.widescreen-centre.co.uk ADVANCED Stay on target while taking astrophotos with this off-axis guider (OAG). The OAG sees the same view as your main scope, increasing precision. The Scops OAG is motorised to stay focused and the supplied software can make filter profiles to ensure the view stays crisp. 2 Forclaz Merino wool tube scarf Price £9.99 • Supplier Decathalon www.decathlon.co.uk Made with Merino wool, this tube scarf can be worn in a variety of ways to keep you warm while observing; wear it around your neck, over your nose or twisted up as a hat. Available in green, blue, red and white. 3 Explore Scientific 10x60 finder and guidescope Price £195 • Supplier Harrison Telescopes Tel 01322 403407 • www.harrisontelescopes.co.uk…

Television Find out what The Sky at Night team have been exploring in recent and past episodes on page 18 Online Visit our website for competitions, astrophoto galleries, observing guides and more Social media Follow us on Twitter, Facebook and Instagram for space news, astro images and website updates Podcasts Listen to our Radio Astronomy podcasts where the magazine team and guests discuss astro news Tablet/phone Get each month’s issue on your Apple or Android device, now with bonus image galleries eNewsletter The best targets to observe each week, delivered to your inbox. Visit bit.ly/skynewsletter Find out more at: www.skyatnightmagazine.com…

HUBBLE SPACE TELESCOPE & PAN-STARRS, 15 MARCH 2021 We can’t blame William Herschel, who first coined the term in the 1780s, but ‘planetary nebula’ is a confusing misnomer. They have nothing to do with planets, but as he had recently also discovered Uranus (which he initially called a comet and a ‘nebulous star’), it’s understandable that Herschel conflated these hazy, disc-like objects with gas giant planets. Planetary nebulae, like the Crab and the Dumbbell, are in fact the death throes of a star which, having exhausted the nuclear fuel at its core, collapses. Its shrugged-off outer layers create a diffuse gas shell, lit from within by a newly formed white dwarf. Abell 78, however, is unusual. Found 5,000 lightyears away in Cygnus, it’s a rare ‘born-again’ planetary nebula. While it…

In May 1977, solar astronomers announced that a new solar cycle was beginning, the 21st since they started being recorded. The solar cycle is a measurement of how sunspot numbers rise and fall every 11 years, created by the motions of plasma deep within the Sun. It takes several months of tracking to determine if the number of sunspots is increasing and to pin-point the precise timing of minimum activity, so while the announcement came in May 1977, the actual start of Solar Cycle 21 came in March 1976. Since then, the increase in the number of sunspots had been rather sluggish, as Patrick mentioned in that month’s show. There was no cause for concern, however; when the maximum arrived in the early 1980s it ended up being more active…

I started astro imaging last April as something to do during lockdown and was hooked. It continues to amaze me what can be observed and imaged in the night sky with very modest equipment. The ‘Moonwatch’ article in the February 2021 issue of the magazine (page 52) suggested Endymion as a target for the month, on either 14 or 15 February. I was unable to capture anything on those nights due to heavy cloud, but I captured this evocative image on the 16th with a Celestron C8-N telescope, Explore Scientific 3x Focal Extender and a ZWO ASI462MC camera, and processed the results with FireCapture, AutoStakkert!, RegiStax and Affinity Photo. With the craters Atlas and Hercules in the foreground, leading up to Endymion and then the Humboldtianum Basin on the limb,…

What drew you to the coast as an astrophotography location? I moved to Romney Marsh in Kent when I was 11, from Dover, and I suppose for me the coast is my go-to place. It’s where I just feel really comfortable and happy. My favourite place to be photographing at night is Dungeness (also in Kent). It’s such an amazing landscape, which is so open and barren, with big skies and lots of really flat land. You can see for miles. What are your favourite celestial objects to shoot over that landscape? I prefer the winter skies and I absolutely love seeing Orion rising up. [I try] to catch things with the different objects that there are down there – the fisherman’s huts and boats and things like that. What…

Which properties are essential for the origin and continued existence of life? And how did Earth acquire them? At a recent online astrobiology conference*, planetary scientist Alessandro Morbidelli (Nice Observatory, France) listed seven key features that could guide astronomers searching for inhabited extrasolar planets. Surprisingly, the slow, protracted growth of Earth, the interaction between Jupiter and Saturn, and the giant impact that formed our Moon may have been decisive factors in making a world that is hospitable to living beings. As Morbidelli says: “You need some luck.” *2021 Online Conference of the Dutch Origins Center, 27–28 January 2021 1. Right distance from their star Obviously, Earth needs to orbit in the Sun’s habitable zone. Many exoplanetary systems have planets much closer to their star, since young, full-grown planets tend to…

Venus now appears in the evening sky after sunset. It’s a bright planet, easy to spot as long as you have a relatively flat west-northwest to northwest horizon. Leave about 20 minutes after sunset before looking for Venus low down. It may be a challenge at first, but it’s like spotting the first star appearing as darkness falls; once you’ve seen it, it’s difficult to miss. If you locate Venus try for Mercury, which appears above and to the left of Venus for all but the very end of the month. On 28 May, Mercury and Venus appear right next to one another, although Venus outshines its neighbour. www.bbc.co.uk/cbeebies/shows/stargazing…

To get the best from a DSLR, a tracking mount is needed. Most of these come equipped with ‘lunar’, ‘solar’ and ‘sidereal’ (star) tracking capabilities, meaning that you can image planets, the Moon, or deep-sky objects and increase your DSLR’s exposure times. It also ensures the object is kept at the same place in your field of view for the entire imaging session. A portable star-tracker or lightweight equatorial mount is a great first step. Because these mounts can track an object for hours, it means you can also stack multiple images. Stacking allows you to increase the signal to noise ratio, reducing the overall image noise. This means you can process the image data more. A comparison between a single frame image (below, left) and stacked image (below, right)…

Make an eclipse shadow model Get to know the interaction between the Moon and Earth during eclipses Here on Earth, when the Sun shines on an object, it casts a shadow. But those shadows aren’t limited to the terrestrial surface: the Moon and Earth cast shadows into space too, and as the two bodies interact with those shadows, it creates lunar and solar eclipses. A lunar eclipse occurs when the Moon passes into Earth’s shadow. This can only occur during a full Moon, when the Moon is on the opposite side of Earth from the Sun. There are two parts to Earth’s shadow; the darker umbra and a slightly brighter penumbra. If the Moon passes fully into the umbral shadow, a total lunar eclipse occurs and the Moon will turn…

The Disordered Cosmos Chanda Prescod-Weinstein Hachette £20 • HB Dr Chanda Prescod-Weinstein’s debut book is two things: a journey into the world of cosmology and particle physics, and a refreshingly eyeopening insight into the too-often exclusionary arena that is science. The book’s main premise is that physics doesn’t just affect us all as a society, but it taps into our natural desire to learn and understand; and yet one group for many centuries, and even to this day, has deemed itself worthy to tap into that knowledge above others. If physics is for everyone, then where is the justification to gate-keep? There are parts of The Disordered Cosmos that read a bit like a popular science book, but the perspective is refreshingly different. It’s not often that physics is presented…

Catch the Eta Aquariid meteor shower and enjoy a view of the Diamond Cross in Carina, the Keel When to use this chart 1 May at 00:00 AEST (14:00 UT) 15 May at 23:00 AEST (13:00 UT) 31 May at 22:00 AEST (12:00 UT) The chart accurately matches the sky on the dates and times shown for Sydney, Australia. The sky is different at other times as the stars crossing it set four minutes earlier each night. MAY HIGHLIGHTS Eta Aquariid meteors are known to be swift, yellow and often show persistent trains. The shower’s radiant – the point at which it appears to a terrestrial observer – is easily visible from the Southern Hemisphere. In May the radiant rises in the early morning, reaching a reasonable altitude by the…