Innholdsfortegnelse for May - June 2020 i Australian Sky & Telescope

WAY BACK IN THE 1970s, one man set off a revolution in telescope design that has not only lasted until the present time, but is still flourishing. His idea was simple – get a basic telescope tube, stick it in a basic wooden box and make it tilt and swivel. Use the cheapest components you can find, even (or preferably) recycled materials, and voila! — you would have an inexpensive instrument that even the most inexperienced of beginners could easily use. That man was John Dobson, of course. Although he didn’t really like having his telescope design, the Dobsonian, named after him, the moniker has stuck and today is universally recognised. Dobsonians have gone from being mostly amateur-built scopes, some of them very rough, to mainstream instruments produced at one…

Isaac Newton realised that the surface of a spinning liquid forms a paraboloid — the ideal shape to focus parallel rays of light into one single point. In 1850, well over a century after Newton’s death, Ernesto Capocci (Naples Observatory, Italy) was the first to suggest the use of a spinning liquid-mercury mirror to construct telescopes. However, there is no evidence that he built one. In 1868, English amateur astronomer Richard Carrington (famous for his observations of spots and flares on the Sun) also dabbled with the idea, but again, it’s unclear whether or not he put it into practice. The first documented liquid mirror was a 35-centimetre one, made in 1872 by astronomer Henry Skey in New Zealand. In 1909, Robert Wood (Johns Hopkins University) built a larger, 51-centimetre…

WHEN Late April 11pmEarly May 10pmLate May 9pmEarly June 8pmLate June 7pmThese are standard times. HOW Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead. FOR EXAMPLE Turn the map so the label “Facing SW” is right-side up. About a third of the way from there to the map’s centre is the brilliant star Canopus. Go out and look…

It’s May, so that means it’s Eta Aquariids time. This shower is one of the best for the year for southern observers, with the radiant in Aquarius located nicely in the pre-dawn northern sky for most observers in Australasia. Its meteors are often swift and bright (some exceeding magnitude 1), with a few leaving trains that can last for minutes. There is also the occasional fireball. Colours tend to be on the yellowish side. Most Moon-free years, I observe from a dark sky location (rated 3 on the Bortle scale) and usually see more than 30 meteors per hour around the time of the peak on May 6–7. In 2014, while observing with fellow meteor shower enthusiasts from Nagambie in Victoria, we recorded 54 meteors in one hour on the…

If beauty is symmetry laced with mystery, then a discovery by a young doctoral student back in 1950 could be one of the most beautiful ever. His discovery has inspired not only generations of professional astronomers but has also intrigued amateurs drawn to arcana of the sky. Arthur Hoag was born in 1921 and spent his early years in the New York City area. His childhood was marred by the tragic death of his mother and younger sister in a barge accident on the Hudson River when he was five. His father died when Arthur was 15, but the lad had the fortunate support of an extended family. Teachers, both in high school and at Brown University, where he graduated in 1942 with a degree in physics, stoked his interest…

Both scientists and starry-eyed entrepreneurs speak of mining asteroids for water and metals. But although these space rocks may someday provide valuable resources, we have a long way to go before that day comes. “We’re talking about the space economy of the 22nd century,” says asteroid expert Richard Binzel (MIT). Water will likely be the first resource utilised, he says. But first we have to learn how to recognise which asteroids have mineable water — something that, given the surprise of a wet Bennu and dry Ryugu, we clearly need to work on. The samples OSIRIS-REX and Hayabusa 2 bring back will tell us how much water the asteroids’ minerals contain and potentially indicate how much future spacefarers could extract globally. “But I don’t predict it for this century,” Binzel…

FOR MORE THAN TWO DECADES I’ve been arguing that Venus — so often voted ‘least likely to succeed’ by astrobiologists — might possibly harbour life. Not on the scorching surface but high up in the clouds, where temperatures are mild, nutrients and energy abound, and droplets consist of water that, while steeped in sulfuric acid, are less acidic than some environments where life is found on Earth. This contrarian position has produced some eye-rolling at conferences, but nobody has come up with a good reason why it’s wrong. And now a funny thing has happened: An international workshop on Venusian cloud life held in Moscow in October 2019, along with several recent publications, appear to have moved the idea from the fringe to near-respectability. Several results contribute to this shift.…

IN 1969, JOHN DOBSON sent an article query to Charles Federer, founder and editor of the US edition of this magazine. Dobson had come up with a new way to build large-aperture telescopes cheaply and effectively. But Federer famously rejected Dobson’s submission, saying, “While your shortcuts undoubtedly help to demonstrate large amateur telescopes, they can hardly lead to satisfactory instruments of the kind most amateurs want in these large sizes.” To say that Dobson had the last laugh is an understatement. Dobsonian telescopes revolutionised amateur astronomy. The majority of large-aperture amateur telescopes today ride upon Dobsonian mounts. I recently wrote a brief article on how to build a modern Dobsonian mount for a hobby killer (AS&T: Feb/Mar. 2020, p. 36). But we haven’t yet published an article on how Dobson…

If you look to the west at sunset in early May, you’ll see Venus — the Roman goddess of love — very low on the horizon. Already gone from our autumn skies are summertime star cluster favourites the Pleiades (the Seven Sisters of Greek mythology) and the Hyades sisters. These three are just a few of the female characters that can be seen in the sky. Let’s look at some more, and then finish with a different kind of astronomical phenomenon. Females in the evening sky. Our May Southern Hemisphere all-sky map is just one page-turn back from this column. Elevated to its highest in the north on that map is the only woman of the zodiac: Virgo, the Virgin. It’s also the longest constellation of the zodiac and the…

MAY 2 Moon 4° north of Regulus 5 Mercury at superior conjunction 6 Moon 7° north of Spica 9 Moon 6° north of Antares 11 Venus 1.4° southwest of Beta Tauri 11 Saturn stationary 12 Jupiter 2° north of the Moon 13 Saturn 3° north of the Moon 13 Venus stationary 15 Jupiter stationary 15 Mars 3° north of the Moon 17 Mercury 7° north of Aldebaran 22 Venus 1° north of Mercury 24 Venus 4° north of the Moon 24 Mercury 3° north of the Moon 27 Moon 5° south of Pollux 29 Moon 4° north of Regulus JUNE 2 Moon 7° north of Spica 4 Venus at inferior conjunction 4 Mercury greatest elong. east (23.6°) 5 Moon 7° north of Antares 9 Jupiter 2° north of the Moon…

Eclipses coming up We’re going to be treated to two eclipses over the next couple of months — one each of the lunar and solar variety. But don’t get too excited; neither will be particularly spectacular. The first will be a penumbral lunar eclipse in the early morning hours of May 6. A penumbral eclipse occurs when the Moon moves through the outer part of Earths’ shadow, the penumbra. These kinds of eclipses are often barely noticeable, with only a faint fading of the lit lunar surface. That will be the case with this eclipse. The event will begin at 3:43am Australian Eastern Standard Time (adjust as normal for your own time zone), with mid-eclipse at 5:25am and the Moon setting before the eclipse is finished. This will be the…

The RF 15-to-35 mm f/2.8 L This new zoom lens has a focal length range and speed perfect for nightscape photography. At 15 mm and wide-open at f/2.8, the lens was clean across the frame with low aberrations at the corners. Off-axis aberrations became more pronounced at the longer focal lengths but were still well-controlled at 35 mm. While vignetting was significant, that can be fixed in RAW processing with Lens Correction functions. The RF 85 mm f/1.2 L Razor-sharp on-axis, even wide open, this short telephoto showed very low off-axis aberrations even at f/1.2, enabling it to grab lots of nebulosity in short exposures and at low ISO speeds. This test shot is with the stock EOS R camera. This is one of the best 85-mm lenses on the…

RASNZ Conference POSTPONED New Zealand’s national amateur astronomy conference. rasnz.org.nz South Pacific Star Party CANCELLED Annual star party of the Astronomical Society of NSW, at a dark sky site. asnsw.com/spsp Asteroid Day June 30 A global day of education to help protect Earth from asteroid impacts. asteroidday.org Star Stuff III July 18 Festival of astronomy in Byron Bay, NSW. starstuff.com.au CWAS AstroFest 2020 July 18–19 Annual gathering at Parkes, NSW, and venue for the David Malin Awards. cwas.org.au Queensland Astrofest August 14–23, 2020 Held since 1993, the dark skies of Camp Duckadang, Linville, attract lots of amateur astronomers. qldastrofest.org.au SASI Public Open Nights 2020 August 28–29 Public viewing at Greenpoint Observatory in Sydney. http://sasi.net.au/public-events/ august-public-open-nights Stargazers Getaway 2020 September 18–20 Star party to be held at Camp Iona, North Otago,…

IN MY NEARLY 76 YEARS on this planet, I’ve travelled a total of 2.8 trillion kilometres. Trillion? Incredible. But you have, too, or with luck and good health you will. Let’s start by counting those 76 voyages around the Sun. Any distance we might have accumulated on the surface of our planet is tiny in comparison. Frequent-flyer kilometres don’t count here! Earth’s orbital speed averages about 108,000 km per hour, so in one year our planet travels 946 million km around the Sun. Multiply that distance by your age. For me, that’s a total of 72 billion km. But there’s more. (Following estimates vary according to source.) Our Sun orbits the centre of the Milky Way Galaxy at 810,000 km/hr, carrying us along with it. One year adds another 7.1…

THE QUESTION OF HOW PLANETARY systems form, and how those processes relate to what we see in our own Solar System, is one of the most fundamental problems in astrophysics and a key piece in the puzzle of figuring out our place in the universe. With the recent success of exoplanethunting missions such as Kepler, we sometimes take for granted that, just a few decades ago, we were unsure whether worlds outside our Solar System even existed. At that time, astronomers used the single known planetary system — our own — to shape our understanding of planet formation. Our Solar System features an orderly setup, with all the planets moving together in a nice flat plane and with plenty of space between orbits. There is also a dichotomy between the…

Mercury (mag. –1.2, dia. 5.5”, May 15) begins May at superior conjunction (ie. on the other side of the Sun) on the 5th, then slowly returns to the post-sunset western sky. Reaching greatest eastern elongation of 24° on June 4, it will remain an evening planet all the way through until late June, whereupon it will descend toward the horizon again and inferior conjunction on July 1. Mercury will pair up with Venus very low on the horizon after sunset on May 22, with the two planets just 1° apart. But they’ll be hard to see — you’ll need a clear horizon and maybe even optical aid in the form of binoculars. Two days later the very thin crescent Moon will join the duo, with all three bodies being within…

MAY First Quarter …… April 30th, 20:38 UT Full Moon …… 7th, 10:45 UT Last Quarter …… 14th, 14:03 UT New Moon …… 22nd, 17:39 UT First Quarter …… 30th, 03:30 UT Perigee …… 6th, 03h UT, 359,654 km Apogee …… 18th, 08h UT, 405,583 km JUNE Full Moon …… 5th, 19:12 UT Last Quarter …… 13th, 06:24 UT New Moon …… 21st, 06:41 UT First Quarter …… 28th, 08:16 UT Perigee …… 3rd, 04h UT, 364,366 km Apogee …… 15th, 01h UT, 404,595 km Perigee …… 30th, 02h UT, 368,958 km…

This year’s favourable apparition of Mars presents an excellent opportunity to witness the development of a transient but recurring Martian feature known as the Mountains of Mitchel, discovered 175 years ago by the founder of the first major observatory established in the United States. Ormsby MacKnight Mitchel was born in 1809 in Kentucky, then a rural outpost on America’s western frontier. In 1825 he secured an appointment to the United States Military Academy at West Point, where the curriculum included surveying, civil engineering and practical astronomy in addition to military subjects. After graduating, Mitchel remained at West Point as a mathematics instructor for three years. He resigned his commission in 1832 and moved to the thriving metropolis of Cincinnati, Ohio, where he studied law and was admitted to the bar.…

Albert Einstein SP Books, 2019 80 pages, ISBN 979-10-95457-05-3 “I AM GLAD THAT I GOT RID OF THE MANUSCRIPT,” Einstein wrote in late April 1925 to his wife, Elsa, “and thank you for doing me this favor of love.” Elsa had solved a problem that her famous husband, who was then travelling in South America, had been unable to solve: what to do with the original manuscript of his magnum opus, “The Foundation of the General Theory of Relativity”. At the time, Einstein was helping establish the Hebrew University of Jerusalem, and Elsa had given the document to a university official who ensured that it later ended up there. The manuscript has been a treasured part of the Hebrew University’s collection since it opened on April 1 of that year.…

LAST YEAR I WROTE about Tom Bartol’s massive equatorial mount. He made it to carry his home-built 25-cm f/5.6 Newtonian telescope, which has a cardboard tube OTA. After the mount was finished, the scope seemed a bit shabby compared to its shiny new support. So one of Tom’s friends, Cary Thomas, offered to help him make a carbon-fibre tube to replace it. Cary is as accomplished at working with composite materials as Tom is with metal. He convinced Tom they could make a lightweight, rigid tube worthy of his machined metal masterpiece. The pair worked out a simple procedure for wrapping layers of carbon-fibre fabric around a cardboard tube that served as an internal form. They started with a 30-cm-diameter tube and wrapped two overlapping layers of duct tape around…

Seventy-nine and counting The discovery of Jupiter’s moons changed our understanding of the Solar System and altered the course of history. Deep sky: Seeing M87’s jet Join the author on his endeavour to observe and sketch the ‘faster than light’ jet in galaxy Messier 87. Night of the Giants Both Jupiter and Saturn will reach opposition in July. Don’t miss our giant-planet observing guide. Test report: Orion’s new viewer Orion’s Premium Linear BinoViewer could change your mind about using using two eyes for stargazing.…