Archive for the ‘Astronomy blog’ Category

Harry sees a Great Prominence Eject

Published by Andrew Jacob on April 15, 2015 No Comments


A Great Prominence Ejects, Sketch and copyright Harry Roberts ©, all rights reserved.

Regular solar observer & correspondent Harry Roberts reports on the ejection of a large prominence from the Sun’s limb.

Sun-watchers have lately been noting the meager prominences seen above the solar limb, hoping for a rerun of some SC23 ‘greats’ perhaps – and current filaments too have been mostly faint. It’s known that global solar fields are currently (mid-SC24) well below SC23 levels.

Thus, it was a happy surprise to see a huge prominence on the Sun’s NE limb on 2015 March 27 (March 26, 23:13UT). “Helio” timings were ‘run’ across its main footpoints (FP), as well as heights, and some of its complex detail was logged; but much fine structure was not recorded. “Helio” © Peter Meadows, soon showed the prominence stretched from lat. 13°N to 34°N, some 21 degrees. It was 87Mm at the highest point, above (FP) 2, the latter sited at +23,287.

This height, well above Zirin’s “50Mm limit” for large ‘quiescents’, implied the prominence was already ejecting. Yet close study and repeat timings showed no increase in height over the next hour – apart from some rearrangement of material mainly between FPs 2 and 4.

Such prominences are, in reality, large disc filaments seen above the limb, and are termed quiet region filaments (QRF): that is, they arise within ‘plumes’ or ‘streaks’ of decayed field trailing behind (i.e. following) areas of active spot formation. The streaks develop over several solar rotations and fields within them are only <100G in strength; i.e. they are long-lived but low power features. Perhaps longevity is the reason QRF grow so large. As the streaks form, they drift BOTH east and polewards; i.e. they drift NE in our example (Fig1).

This means that in Fig1 the right-hand side (i.e.N) parts of the prominence are likely well behind the solar limb (at Ln289) – perhaps 20° behind the limb (~Ln270°); indeed the fine detail of the prominence and its decreasing height towards the N suggests this. The highest point on the prominence was above FP2, presumably right on the limb, and declined northward. There was no major change in the structure when the session ended at 00:0UT.

Ejection? The structure was again studied (Fig2) at 05:46 on Mar 27UT (5h50m after Fig1), when changes were seen: but bigger ones had been expected. It was brighter and the tallest part of the feature now lay between FPs 3 and 4, where it was 98Mm high, and the ‘arch’ between them was wider and higher: no doubt the ejection was slowly underway. Yet the setting Sun’s altitude was (at 06:35UT) just 15°: with wind and poor seeing the session ended.

Fig3 is an enhanced ©GONG Halpha image made at the Udiapur station. The robotic ‘scopes do not track ejecta, and have a field of view (FOV) just 100Mm above the solar limb. At 11:50UT (12h15m after Fig1) we see the ejection is well advanced, with the main arch lifted mostly above the FOV (broken arrow), though some around FPs 1 and 4 is still attached.

Questions. Filaments are known to regenerate quickly, as the ejection removes the accumulated material but not the ‘filament channel’ nor the progenitor ‘streaks’ of old sunspot polarity. Yet, since the event, there has been no sign of filament regeneration at the site; perhaps in time?

What of its earlier life? My logs show a large but faint filament nearing the west limb on March 10 UT, a possible precursor, but cloud prevented viewing around the 13th when a big prominence may have decorated the NW limb. The site should return to the west limb around April 5: what will we then see?

Harry Roberts is a Sun and Moon observer, a regular contributor to the Sydney Observatory blog and a member of the Sydney City Skywatchers.

21_Sunset_Nick LombThis morning at 9:45am AEDT the Sun crossed from the southern to the northern part of the sky. On this day daytime and nighttime are almost equal at 12 hours each. Daytime though is a little longer than 12 hours due to the size of the Sun’s disc and because the atmosphere bends the light from the Sun.

Post from the Australasian Skyguide, written by Dr Nick Lomb.

Sunset occurs when the top edge of the Sun appears to sink below the horizon. Photo Nick Lomb

Dancing Curtains of Light

Published by Melissa Hulbert on 3 Comments

From the 13-17 March I was in Tromso, before heading further north for the eclipse. The 14th was the first chance of a clear night and friends and I joined an aurora chase out of Tromso into darker, hopefully clear skies. We were not disappointed. About 9pm soft auroral light started and then slowly intensified.

Dazzling curtains of light danced overhead on 14 March 2015.

Dazzling curtains of light danced overhead on 14 March 2015.

For the next few hours, dancing curtains of light gently swirled and moved above us and not only were we treated to the usual green and often red auroras but also purple and yellow.
The following night was unfortunately cloudy (it turns out the 14th and 15th were two of the best nights of the season until the activity of March 17, though this occurred during the daytime in Svalbard) but the night of the 16th was clear and we joined friends on a chase to Kvaloya. Upon arriving we immediate looked up and there again the dancing curtains of light were there. Although slightly fainter than the 14th, the purple and yellow colours in the auroras were stronger and along with these colours and the usual green and red, we also saw a deep turquoise blue from time to time.

Subtle purples and yellows were a feature of the aurora on 16 March 2015.

Subtle purples and yellows were a feature of the aurora on 16 March 2015.

Both nights have been a highlight of our Nordic adventure (along with a stunning solar eclipse yesterday) and something my friends and I agree we’ll never forget.

There are currently reverberations happening from the March 17th Coronal Mass Ejection (CME) and we hope to try for some Svalbard auroras tonight if the lovely (but cold, -26.6 degrees this morning) weather holds!

Aurora over Kvaloya on 16 March 2015.

Aurora over Kvaloya on 16 March 2015.

Totality on Ice

Published by Melissa Hulbert on March 21, 2015 1 Comment

Today dawned cold (-24 degrees), bright and clear and we headed off early on snowmobiles to a remote area away from Longyearbyen. High on the mountain at Fjordnibba, overlooking Tempelfjorden was the perfect place to observe the eclipse from.

Fjordnibba, our observing site for today's solar eclipse.

Fjordnibba, our observing site for today’s solar eclipse.

The partial phases passed quickly and as the diamond ring approached, amazing shadow bands were seen across the snow. Totality once again passed all too quickly and the second diamond ring signalled the end of totality. To be in such an amazing, remote and wonderful place with crystal clear skies and watching the twilight at totality lighting the mountains has made this one of the most memorable eclipses I have seen.

Widefield image of Totality. Venus is visible in the top right of the image.

Widefield image of Totality. Venus is visible in the top right of the image.

Diamond Ring, just before totality.

Diamond Ring, just before totality.

Seeking Totality

Published by Melissa Hulbert on March 20, 2015 No Comments

I’m currently sitting in a well heated room, snow and ice along the window, overlooking an icy fjord. Where am I? I’m at latitude 78 degrees north on the island of Svalbard where the temperature outside is now a balmy -15 degrees. Thousands of astronomers and umbraphiles have descended here to witness one of the most spectacular natural wonders, a total solar eclipse. After two days of cloud, today dawned bright and clear, in fact, today is only the third day the Sun has been seen here since it returned to the sky on 24 February. We are all hoping Mother Nature will be kind enough to provide another stunning day tomorrow for the eclipse.

Total Lunar Eclipse 
Saturday 4 April 2015, 9pm – midnight.




Download this Fact Sheet for details about timing: April 2015 Total Lunar Eclipse Fact Sheet


Lunar Eclipse photo by Geoff Wyatt, 8 October 2014

Lunar Eclipse Live 
Sydney Observatory is well placed to view the April lunar eclipse which appears in our north-eastern sky. Sydney Observatory will be live streaming the total Lunar Eclipse. Dr Andrew Jacob, curator of astronomy , will be at Sydney Observatory directing the live feed from 9pm to 11:30pm local time (10-12:30 UT) from our 16-inch north-dome telescope. Here is your YouTube link. Whilst waiting for the eclipse you can hear Astronomy guide, Brenan Dew, explain the Lunar Eclipse and Aboriginal Astronomer, Willy Stevens, discuss how his people explained Moon phenomenon.

Total Lunar Eclipse Event
Saturday 4 April
9pm – midnight

If you have booked and want to cancel please email before the event starts.

We are running an event on-site which focuses on telescope viewing of the eclipse and information sessions. Snacks, tea, coffee and hot chocolate available on site. Because it is a late night this is suggested for ages 15 and over. Cost: $59 family, $22 adult, $15 child; members $48 family $18 adult $12 child. Concessions $18. Bookings and pre-payments are essential. BOOK ONLINE NOW! For enquiries please call 9921 3485.

Media Enquiries only please call 9921 3485/ 9921 3484 or 0411137102.

Even if you can’t visit Sydney Observatory during the Total Lunar eclipse keep in touch and lets us know about your eclipse experience via Sydney Observatory Facebook or @sydneyobs Twitter.


Melissa Hulbert, Sydney Observatory, took this image of Moon in eclipse showing the spectacular red colour.


The full Moon reddened during the total lunar eclipse of October 8 2014. Image copyright Geoff Wyatt.

The full Moon reddened during the total lunar eclipse of October 8 2014. Image copyright Geoff Wyatt.

Lunar eclipse 28 August 2007, photos by Geoffrey Wyatt

Lunar eclipse 28 August 2007, photos and animation by Geoffrey Wyatt

Total lunar eclipses
Dr Nick Lomb, Sydney Observatory’s consultant astronomer and curator, and Sarah Reeves, astronomy guide, provided the following helpful explanation. On average there is an eclipse of the Moon every eight months, with a little under half of these total. The actual number of lunar eclipses in a year can range from none to a maximum of three. A total eclipse of the Moon is visible from Australia on average every 2.8 years. In Australia, a total lunar eclipse will occur on 4 April 2015. In parts of the Northern Hemisphere there will also be a total lunar eclipse on 27 September 2015.

Why the Moon is red during a total eclipse
The Moon will appear red during totality because red light from the Sun is bent by the Earth’s atmosphere onto the Moon. The light is red as other colours such as blue are scattered in all directions leaving red, just as at sunset. Another way of putting it is that seen from the Moon the Earth is dark, but surrounded by an atmosphere lit up by either by sunset or dawn. Whether the Moon will go red and how dark a red depends on atmospheric conditions at the time of the eclipse. This post about the 2007 total lunar eclipse will give you some idea of what we can hope to see on the night.

How do eclipses occur?
Eclipses of the Moon occur when the Moon moves into the shadow of the Earth. There are three kinds of lunar eclipse – penumbral, partial and total. Penumbral eclipses occur when the Moon falls in Earth’s penumbra (the fainter part of our shadow). A partial eclipse occurs when a portion of the Moon is covered by the Earth’s umbra (the darkest part of our shadow), and a total eclipse occurs when the entire Moon is inside the Earth’s umbra. When the Moon is fully immersed in the dark part of the shadow we see a total eclipse of the Moon. At such times the eclipsed Moon usually takes on a dark reddish colour from the light bent or refracted onto the Moon by the Earth’s atmosphere. When the Moon is only partially immersed in the dark part of the shadow we have a partial eclipse.

Eclipse basics

How eclipses of both the Sun and Moon occur. Sketch Nick Lomb

An eclipse of the Moon can only happen at full Moon phase. It does not happen every month as the path the Moon takes around the Earth is tilted by about 5° to the path the Earth takes around the Sun. Hence at full Moon the Earth’s shadow usually falls below or above the Moon.

What is the history of Moon eclipses?
Eclipses of the Moon first provided proof that the Earth is a globe as the edge of the Earth’s shadow moving across the Moon is always part of a circle. This was noticed by the Greek philosopher Aristotle who lived in the fourth century before our era. According to ancient Chinese legend an eclipse of the Moon occurs when a dragon begins eating the Moon. Hence the tradition in China during eclipses was to make as much noise as possible by banging on drums and pots to scare away the dragon. This technique has so far succeeded on each occasion.

Viewing a lunar eclipse

Unlike solar eclipses, a lunar eclipse can be seen from anywhere that is experiencing nighttime when the eclipse occurs. Lunar eclipses are also safe to view with no special eye protection, and fun to photograph. For those who missed last October’s event, you won’t have to wait too long – the next total lunar eclipse is due to occur on 4 April 2015.

Check out our free monthly sky guides including podcast, sky map and transcription, giving you a guide to highlights in the night sky for each month of the year.

Check out also our free Moon phase calendar.

You can engage with us by commenting on this post or through FaceBook and Twitter.

Happy π Day!

Published by Toner Stevenson on March 14, 2015 No Comments
Image courtesy of Delft University of Technology via

Image courtesy of Delft University of Technology via

That’s right! Today is the day that we celebrate the mathematical constant π (Pi) – 3.141592653589793232384626433…

But why is today Pi Day? Because… if you write the date in the MM/DD format, today is 03/14 and 3.14 are the first three digits of the irrational number that is the ratio of a circles circumference to its diameter. That is: π. But things are even better for π day this year, because in the MM/DD/YY format, this year is 03/14/15, which is π to 5 significant figures: 3.1415. If you want to be even more meticulous, wait until 9.26 (am or pm) and 54 seconds (if rounding up) to get an even bigger dose of π. At this instant the date and time will be: 3/14/15, 9:26:54, which is π to 10 significant figures: 3.141592654! This is as good as mathematical dates can get!

But wait there’s more! Today is not the only day that we can celebrate π in the calendar year, because in just 130 days time it will be π approximation day, or the 22/7 (DD/MM), which as a fraction is a common approximation of this irrational number π.



This post was written by Brenan Dew, Astronomy Guide at MAAS – Sydney Observatory



120 Years of Astronomy Seminar – open to all 
Saturday 14 March 2015, 5pm to 8:30pm
Organised by Sydney City Skywatchers , the city’s astronomy club, and held at Sydney Observatory this is an opportunity to hear great speakers focus on the contributions of amateur astronomers.
Cost: $10 (includes refreshments).
Numbers are limited so reserve your seminar seat today by emailing:

5pm Introduction by Sydney City Skywatchers President, Mike Chapman

5:10pm Keynote presentation by Professor Wayne Orchiston
‘John Tebutt and the Formation of Sydney’s Earliest Astronomical Societies’

6:10pm Refreshments and discussion

6:30pm Sydney City Skywatcher presentations:

•  Monty Leventhal OAM, Steavenson Award ’22 years of Solar Observing’
•  Dr Nick Lomb, IMAgine Award, ‘Closing Encounters: the BAAs attempt to save Sydney Observatory’.
•  Toner Stevenson, PhD candidate  ‘Women in Amateur Astronomy in Australia’
•  Harry Roberts, Mike Kerr medal & McNiven Award ‘Astronomical Illustration’

8pm Concluding remarks

8:30pm Optional dinner at the Hero of Waterloo
(not included in seminar cost see website for menu and costs )

March 2015 night sky guide transcript and sky chart

Published by Melissa Hulbert on March 1, 2015 7 Comments

To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month. This month’s guide is presented by Geoffrey Wyatt, Sydney Observatory’s Education Program Producer.

If you’re not sure how to find your way around the night sky, Geoff presents some easy tips for how you can find angles above the horizon just using your fist, fingers and arm – and it doesn’t matter how old or big you are as the sizes of your fist, fingers and arms are proportional with the rest of you – so it works for everyone!

Geoff takes us on a tour of the stars and constellations prominent in the March sky, including the bright star Aldebaran in the constellation of Taurus, and the bright star Betelgeuse in the constellation of Orion.

Geoff’s fascinating talk is enriched with historical and mythological astronomical references – ranging across cultues including Indigenous Australian, Arabic and ancient Greek.

We provide an embedded sky map (below – please be patient as it can take a little while for it to load) and a March 2015 night sky chart (PDF) which shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.

READ THE TRANSCRIPT (after the jump)


A Sydney City Skywatchers Presentation held at Sydney Observatory

6:30pm, Monday 2 March, 2015
Professor Wayne Orchiston (National Astronomical Research Institute of Thailand) presents:
‘Joseph Ward and the Historic Cooke Refractor at the Wanganui Observatory, New Zealand’

Joseph Ward c 1921. Image source

Until quite recently, the historic 9.5-in Cooke refractor at the Ward Wanganui Observatory in the North Island city of Wanganui was the largest refracting telescope in New Zealand. Manufactured in 1859, this is an internationally-important telescope since it is a ‘type specimen’ (in zoological parlance) and features the first all-metal English equatorial mounting ever made. The telescope was used for serious research in England during the nineteenth century, and subsequently in New Zealand after it transferred ‘down under’ in 1902. The man responsible for bringing the telescope to New Zealand was Joseph Ward (1862–1927), who is a remarkable character. He not only discovered many new double stars with the Cooke telescope, but also made refractors and reflectors on a commercial basis. His largest telescope was a 20.5-in Newtonian reflector, which has an interesting history. Professor Orchiston will discuss the English and New Zealand histories of the historic Cooke refractor, and Ward’s bid to make astronomical telescopes more widely available throughout New Zealand at a reasonable price.

Sydney City Skywatchers are very grateful to the Donovan Astronomical Trust for helping fund Professor Orchiston’s visit to Sydney.

Bio: Wayne Orchiston was born in New Zealand, but grew up in Sydney. In 1959 he joined the NSW Branch of the British Astronomical Association, was elected to the Committee at the age of 16, and eventually served as President. Later he was elected an Honorary Life Member when the Branch closed and the Sydney City Skywatchers was formed. Wayne’s early observational interests were in sunspots, meteors, the planets and variable stars, but he also developed a passion for the history of Australian astronomy and particularly the achievements of the Branch’s first President, John Tebbutt of Windsor.

Wayne has B.A. Honours and Ph.D. degrees from the University of Sydney and formerly worked at the CSIRO’s Division of Radiophysics, Sydney Observatory (part-time), Victoria College (later Deakin University, in Melbourne), the National Observatory of New Zealand (as Director), the Anglo-Australian Observatory and the CSIRO’s Australia Telescope National Facility (in Sydney), and finally James Cook University (Townsville) before joining the National Astronomical Research Institute of Thailand (NARIT) a little over two years ago, where he is a Senior Researcher. He is co-founder and Editor of the Journal of Astronomical History and Heritage, and in 2013 the IAU named minor planet 48471 Orchiston after him.

SYDNEY CITY SKYWATCHERS welcome members, new members and those interested in astronomy in the city to this presentation. There is a small supper charge $2 Members/ $5 non-members.



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