Innholdsfortegnelse for September - October 2021 i Australian Sky & Telescope

THE SATURN SYSTEM IS BEAUTIFUL, and beautifully weird. The magnificent rings inspire an ‘Oh wow!’ when seen through even small telescopes, in part because they’re so unexpected, almost as if the planet had sprouted ears. Every giant planet in the Solar System has rings of some sort, but only Saturn’s are so vast and so brilliant, composed almost solely of highly reflective water ice. But the rings aren’t the only unusual thing about this planet. The diversity of its extended family of satellites is unique among Saturn’s giant brethren. Unlike Jupiter, with its four heavyweight moons and scores of small ones, Saturn has a third kind of companion: midsize moons, with diameters of 300 to 1,500 km, or a tenth to almost half the span of our Moon. Tucked between…

NEPTUNE REACHES OPPOSITION ON September 14 in the star-sparse wilds of eastern Aquarius, near the Circlet of Pisces. Despite being more than 4.3 billion kilometres away, the Solar System’s most remote major planet shines at magnitude 7.8, which means you can claim it with 10x50 binoculars from any reasonably dark location. As if to avoid the astronomical paparazzi, the distant blue world stays clear of any bright stars that could easily give away its location as it slowly treks westward in retrograde motion. As the chart opposite shows, only a couple of 6th-magnitude stars mark its path during the current apparition. I recommend trying to catch Neptune on the night of September 23–24 when it glides just 1.6’ south of 6.3-magnitude HD 221148. One of my favourite Neptunian observing activities…

We’ve taken a look at U Tucanae before, back in our Nov/Dec 2013 issue, when we recalled its discovery by Williamina Fleming in 1897. This issue, we’ll use this long-period variable star as a gateway into one of our neighbouring galaxies, the Small Magellanic Cloud ( SMC). Any observing session begins best with the naked eye, so start with the globular cluster 47 Tucanae — plotted on the all-sky chart on the centre pages of this issue. Then, using the chart provided at right, use your telescope’s finderscope to locate Lambda Hydri to the south of 47 Tuc. The finder chart also shows U Tuc, 494 light-years distant and which, at maximum light, can be easily seen through a finderscope. U Tuc’s brightness varies from magnitude 8.0 to 14.8. Now,…

STANDALONE GUIDER StarAid announces its latest autoguider for deep-sky astrophotography. The StarAid Revolution – Revision B (890€, or about $1,400) promises hassle-free astrophotography with AI-powered guiding. This 39-mm x 63-mm guider is designed around a Sony IMX290LL CMOS detector with a 1,920 x 1,080 array of 2.9-micron pixels. It is controlled using a Windows PC or your smartphone connected through integrated Wi-Fi and is powered through its USB-C port (power supply not included). Its nosepiece fits standard focusers and is threaded to accept 1¼-inch filters. The Revolution automatically identifies the location at which it is pointed, and it aids with polar alignment as well as executes fully autonomous, multi-star tracking. Cables and port splitter are included. StarAid staraid.ai CARBON-FIBRE APOCHROMAT Stellarvue adds a new model to its extensive line of…

These economy models are good for beginners on a budget. Despite their low prices, all have 18 mm of eye relief. (All prices quoted in this article are approximate retail prices, as advertised by various outlets on the Internet.) Left to right: Celestron Cometron ($110) This model suffers from a vignetted field due to undersized prisms. Stars are sharp in only the central 50% of the relatively narrow (48°) apparent field. Great for kids and casual users. Orion Scenix ($200) With eyecups rolled down, eye relief is just enough for use with eyeglasses. The apparent field is 50°, yielding an actual field of 7.1°, typical for 7×50s.…

LAUREN WINGERT HAS MODIFIED every scope she’s owned — flocking the inside of the tubes, making dew shields, installing cooling fans and adding manual setting circles. She even converted her 25-cm Orion IntelliScope to send its position signals to a tablet running SkySafari to make a push-to scope with visual feedback. Lauren liked that setup so well that when she purchased Mel Bartels’s famous 32.5-cm Zip Dob, she wasted no time adding digital setting circles to that, too. There was just one problem: The Zip Dob lacks physical horizontal or vertical pivot points to which to attach the encoders. The scope sits on a flex rocker and ground ring, so there’s nothing but space where the azimuth pivot bolt would be on a traditional Dobsonian, and it uses its own…

ALMOST 60 YEARS AGO NOW, my dreams of playing competitive basketball were shattered. Torn ligaments from a careless dive for a loose ball effectively ended my career. Rather than shooting hoops, I faced knee surgery followed by weeks of physical therapy. To pass those long months that year, I decided to read Jean Texereau’s book How to Make a Telescope and build my own. Grinding, polishing and testing a 15-cm mirror helped me make it to March. Building an optical tube assembly and mount helped me make it to May. Observing Saturn as my ‘first light’ object completed my telescope-building project — and unexpectedly changed my life. I had seen bigger and better images of Saturn in the pages of magazines, but, as all AS&T readers know, there’s something magical…

THE POWERFUL FLASHES of fast radio bursts (FRBs) are so fleeting, they’re hard to find. Astronomers had detected only about 140 of them since 2007. But the first data release from the Canadian Hydrogen Intensity Mapping Experiment (CHIME), presented on June 9 at the virtual meeting of the American Astronomical Society, more than tripled that number with 535 FRBs, including 61 bursts from 18 previously reported repeating sources. After CHIME scans the whole sky visible from its location in British Columbia every night, astronomers use digital signal-processing to ‘focus’ on individual signals. Yet the telescope only sees the tip of the iceberg: Based on the first year of data, collected between 2018 and 2019, the CHIME/FRB Collaboration calculates that some 800 bright bursts occur every day. The radio flashes CHIME…

Who first proposed that the Sun, rather than the Earth, lay at the centre of our local bit of the cosmos? That the Sun was the hub around which the planets, the comets and the other celestial bodies moved? Most people would say Copernicus, just under 500 years ago. He certainly challenged the prevailing world view — endorsed by great ancient minds such as Aristotle and Ptolemy, and blessed by the Church — that the Earth, as home to Man, lay unmoving at the centre of the entire cosmos… all of which, including the distant ‘fixed stars,’ rotated around the Earth once per day. This vision, which also appears to conform with common sense and everyday experience, had been undisputed for more than 1,500 years, until Copernicus summoned up the…

THE MILKY WAY can be rather difficult to see these days, due to light pollution. Many in urban areas don’t get a good look at it at all, and it can even lose some of its lustre in rural locations. I can’t discern much of our galaxy’s dusty plane from where I live, but in 2019 I was fortunate to attend a star party under very dark skies where I was able to gaze upon the beauty of the Milky Way for the first time in quite a while. People in ancient cultures were lucky, because they could see this wonder regularly. There wasn’t much light after dark, and their skies were brilliant with the glow of countless stars when clear of clouds on moonless nights. Shadowlike swaths of dusty…

If you’re new to astrophotography and struggling to get pleasing results, I can help. Presented here are a few tried-and-true tips to help you take better astropics whether you’re shooting the night sky with a DSLR and lens or photographing deep sky marvels with a specialised astrocamera and telescope. These pointers are mutually supporting to help you obtain that “Oh, wow!” image. Familiarise yourself with all four tips and apply them together on your next imaging session. 1: SAAS! (Shoot, assess, adjust, shoot) I formulated the SAAS acronym for my own purposes because it succinctly describes the astrophotography process. No matter what equipment you use, a consistent process is key. After carefully framing your subject, focusing and selecting your camera settings, Shoot your image. That part is obvious, but it’s…

When the moon is in the Seventh House And Jupiter aligns with Mars Then peace will guide the planets And love will steer the stars This is the dawning of the Age of Aquarius — From the song Medley: Aquarius / Let the Sunshine In (The Flesh Failures) featured in the 1967 musical Hair. Astronomically, the Age of Aquarius won’t begin until the vernal equinox point — where the Sun is found at the start of spring — enters the boundaries of the constellation Aquarius, as established by the International Astronomical Union in 1930. According to the Belgian astronomer and mathematician Jean Meeus, that won’t occur until the year 2597. Highlights of Pisces. So, for the next several centuries, this point on the celestial sphere is located in Pisces. What…

Impact craters are by far the most abundant landforms on the Moon. Thousands of them having diameters larger than about 5 kilometres are visible through almost any backyard telescope. All can be classified into three fundamental types by inspecting their interior zones — the walls, floors and central peak elevations. Most lunar craters are bowl-shaped simple craters with diameters up to about 15 km. They have featureless walls, rounded or flat floors, and no central hills. Piazzi Smyth, for example, is a 13-km simple crater in southern Mare Imbrium. Complex craters are larger than simple craters, and you need to observe their interiors closely to separate them into their two subgroups. First are complex-slump craters typically 15 to 35 km wide. Their interior walls start with a steep scarp and…

On September 26, 1785, William Herschel discovered a trio of nebulae along the Pegasus-Pisces border, which he recorded as II 439, II 440 and III 435. John Louis Emil Dreyer listed these three objects in his New General Catalogue of Nebulae and Clusters of Stars (published in 1888) as NGC 7619, NGC 7626 and NGC 7623. The three galaxies anchor a medium-compact group known as the Pegasus I cluster that lies about 170 million light-years away. The collection occupies the southwestern end of the Perseus-Pisces Supercluster. Pegasus I has been extensively studied since the 1920s, and in that time our understanding of its membership has evolved somewhat. A 1982 paper included 75 member galaxies, but lately that number has shrunk to perhaps as few as 13. More recent research has…

THE ADVANTAGES OF BINOCULARS over telescopes are many — especially for night-sky novices. Not only are binoculars affordable, but they’re also easy to use thanks to the wide fields of view they offer and their right-side-up image orientation. Everyone starting out in astronomy should have a good pair of binoculars. If you’re a veteran observer, you’re already aware of these advantages, but you might be using the same well-worn pair you’ve owned for decades. Every aspect of binocular performance — field of view, eye relief, optical coatings and build quality — has improved in recent years. It just might be time to consider an upgrade! Here’s my up-to-date guide to buying the best binoculars for astronomy. Aperture and power Even otherwise commendable review websites often assume that the best stargazing…

These models provide fine performance for under $400 and will please both first-time buyers and experienced observers looking for a budget upgrade. All have apparent fields of 60° to 65°. Left to right: Pentax SP ($170) These have a wide, 65° apparent field. The shallow eyecups don’t roll down easily, and the 12-mm eye relief is just adequate for views without glasses. Another economical choice for kids. Bushnell Legacy WP ($230) The eyecups twist up and down. Stars are sharp in the central 50% of the 63° apparent field. WP stands for waterproof; weight is 970 grams. Bresser/Alpen Magnaview (US$120) Sold in the US through Explore Scientific, the Magnaview has twist-up eyecups and the widest apparent field at 65°, with stars sharp over the central 50%. Celestron Ultima (US$140) At…

The shortlist of entrants for the Royal Museums Greenwich Astronomy Photographer of the Year competition has been released. This is the competition’s 13th year, and it just keeps getting bigger, attracting more than 4,500 entries from 75 countries. Just as with past years, the entries for 2021 cover the gamut of astrophotography, from solar to lunar, from deep sky to startrails, from planets to nightscapes. The winners will be announced during an online event on September 16 (UK time). Visit rmg.co.uk to view the shortlisted photos and for updates on the prize ceremony. Closer to home, the winner of the David Allen Prize for communicating astronomy to the public, has been awarded to astronomer Geraint Lewis. Geraint has a knack for tackling complex scientific topics in engaging manner and making…

In 2018, a team of astronomers discovered a super-Earth about 6 light-years away, hidden in the meager light of its red sun, Barnard’s star. Now, a new study to appear in the Astronomical Journal challenges that claim. In the original study, Ignasi Ribas (Institute of Space Sciences, Spain) and colleagues analysed two decades of radial velocity measurements, which showed the star’s slight motions toward and away from us. Within those data, Ribas and colleagues saw the repeated signal of a planet’s gravitational back-and-forth pull as it circled its star every 233 days. But in a new analysis, which includes observations from the recently minted Habitable-zone Planet Finder on the Hobby-Eberly Telescope in Texas, graduate student Jack Lubin (University of California, Irvine) and colleagues concluded that stellar activity might have masqueraded…

ASTRONOMERS HAVE CAPTURED 226 million galaxies up to 7 billion light-years away in an area covering about one-eighth of the entire sky. This treasure trove of data provides the best-ever probe of cosmic evolution and illuminates the role of dark matter and dark energy in shaping the large-scale structure of the universe. The Dark Energy Survey (DES) started back in August 2013. On May 27, the international collaboration behind the survey posted 30 scientific studies covering the first three years of observations. These papers will appear in the Monthly Notices of the Royal Astronomical Society. (Although the Dark Energy Survey was completed in early 2019, the collaboration is still processing the last three years of data.) To map out large-scale structure, DES scientists start with individual galaxies. Based on a…

THE PATH TO BECOMING an orderly planetary system is a messy one. As young stars collapse onto the main sequence, dust grains in orbit around them begin their long journey toward planethood, racing to cling together and collect gas before furious stellar winds whisk it away. Magnetic fields seize ionised gas and siphon it onto the star’s surface, causing hotspots that blaze in X-rays. Nearby stars can complicate matters, swinging by and warping the dust disk. All this warping, siphoning, collecting and collapsing has created plenty of work for amateur and professional astronomers alike, who have been observing and modelling the behaviour of pre-main-sequence stars for decades. Pre-main-sequence stars can vary in brightness on timescales from minutes to years and at essentially all wavelengths, but the reasons for these variations…

DISASTERS SUCH AS EARTHQUAKES AND HURRICANES are common in Puerto Rico. Only about 180 by 60 kilometres in extent, the small island lies 1,600 kilometres southeast of Miami, far from any major landmass. The Atlantic Ocean beats against its northern shores, and the placid Caribbean strokes its southern coast. Despite the dangers, Puerto Rico is a popular tourist destination and home to 3.2 million US citizens, a resilient and diverse population long proud of the world-famous 305-metre-wide radio telescope at Arecibo Observatory. But at 7:00am on December 1, 2020, their resilience was severely tested. At that moment the support cables above the dish snapped, and the 900-ton antenna platform suspended above the dish plummeted into it in a mangled mass of steel. The crash triggered a nearby seismograph accustomed to…

I grew up in a flat rural area, so mountains have always had a powerful and exotic allure for me. My favourite views when I’m in a mountainous area come as I start to descend. I’ll drive around a corner and suddenly, through a gap, I’ll catch a glimpse of some distant patch of flat land and feel like I’ve received a privileged view through to the heart of nature. This is also how I like to imagine we see M24 in Sagittarius, the Archer. M24 looks like an open cluster, but it isn’t. Rather, it’s a star cloud — a vast congregation of stars in one of the inner spiral arms of the Milky Way Galaxy. These stars are spread between 10,000 and 16,000 light-years along our line of…

Saturn’s rotational axis tilts by almost 27 degrees to the plane of its orbit, giving the ringed planet a full array of Earth-like seasons. While seasons on Earth last only three months, Saturn ponderously circles the Sun once every Earth 29 years, so each season lasts for more than seven Earth years. Saturn’s dusky belts and bright zones resemble those of Jupiter but are comparatively muted in contrast and bland in appearance. At the lower temperatures that prevail at the ringed planet’s greater distance from the Sun, clouds form deeper in its colder atmosphere. The planet’s weaker gravity greatly reinforces this thermal effect. Although Saturn is just 15% smaller in diameter than Jupiter, it’s only 30% as massive. Jupiter’s atmosphere is pulled much more powerfully toward the centre of the…

EARLY OBSERVERS OF NEBULAE — among them noted American astronomer E. E. Barnard and German astrophotography pioneer Max Wolf — noticed that bright and dark cosmic clouds often cluster together. William Herschel famously referred to the complexity of such objects when he described the Rho Ophiuchi cloud as a “hole in the sky!” He also noted the positional relationship between dark nebulae and rich star clusters that we now refer to as globular clusters. The Rho Ophiuchi region is a well-known example of this juxtaposition, but there are many more. Let’s begin our exploration of collections of some of these nebulae, starting at southern declinations and gradually moving northward. First stop: Corona Australis Head for the boundary between the Southern Crown and Sagittarius, a bit less than 1° west-northwest of…

Fields of view are sometimes expressed in terms of metres at 1,000 metres. Convert metres @ 1,000 metres into an actual FOV in degrees by dividing by 17.5. For example, binoculars that advertise 77 metres @ 1,000 metres would yield a true field of view of 4.4º.…

One of the many things I learned as a novice astronomer was that if I didn’t have a list of objects to view when I went into the backyard with my telescope, I wouldn’t see much. I’d look at M13 or M42 or a few other bright wonders and end up calling it a night. Fifty years later that hasn’t changed. I still need a list if I hope to see much. And that’s where planning software comes in. When most beginning observers think about astronomy software, they often envision a program that displays a rendition of the night sky on the computer. These planetarium programs can be attractive, but many of us find observation planning software even more useful. A planning program is essentially a huge database (many now…

Who doesn’t love a comet? These otherworldly visitors episodically swing by the Sun, only to be flung back into icy outer space. How exactly do they find their way to us from the Solar System’s outer reaches? The answer may well lie with the famous Comet 29P/Schwassmann-Wachmann 1. Gateway objects. Astronomers have identified a region just beyond Jupiter that channels most of the faraway Kuiper Belt objects into the inner Solar System, where they then scurry busily about flouncing fancy tails. Objects entering this ‘comet gateway’ region are called Centaurs, and the most sought-after of these is 29P. At about 900 million km from the Sun, 29P is one of the most distant objects to show heightened comet activity. Normally around magnitude 16–17, the iceball always exhibits a dust coma,…