In this issuePage 1: President’s messagePage 2: Calendar/Communications Astronomy on the RunPage 4: The Wi(l)der the Shot...Page 6: Paul’s CornerPage 7: The Battle of the MeridianPage 8: Planet Hunting

Journal of the Northern Sydney Astronomical Society Inc. Volume 24 Number 2 April 2013

Hello all Members and Prospective Members.

In referring to prospective members, I am mindful of the very successful first session of the current New Astronomers Group course, held on the fourth Tuesday of March, which will hopefully translate into full membership on the part of some of those visitors who attended.Credit for the record attendance is due to Peter Korber who relentlessly pursued the North Shore Times journalist until he achieved his aim of an article and photograph. Yes, we know the photo was somewhat dubious, but it was a photo.

At this NAG first session, the basics of telescopes were explained to the 39 Members and visitors attending. It was a very successful night and full credit for the presentation must go to Bob Fuller and Geoff Unsworth.Quite a few members present also added to the depth of knowledge and impressive equipment on hand.

NSAS is travelling well, with some ups and downs in the various activities we pursue, but as usual we could do with extra participation pretty much across the board.It would also give the group a much more solid feel if the monthly meetings were better attended. Bob Fuller is continuing to attract excellent speakers who deserve as full an attendance as we can reasonably provide. Remember too that the problematic acoustics at Regis Hall are a thing of the past, as all our meetings are now conducted in the classrooms below the Hall.

Our two longest standing activities, Observations (under the supervision of Tim Herridge) and Outreach, continue to go well.Observations is a very settled activity and there are always devoted observers turning up; they would be delighted to have Members and interested members

President’s Messageof the community turn up to have a look at what is happening up there and explain the workings of the different types of telescopes.

The Committee is currently considering a discussion paper on how Outreach can best work.At the heart of the matter are some fairly fundamental questions such as: what is our capacity (personnel and equipment) to undertake this function; how many events can we reasonably manage; what should be considered our “permanent” commitments; what level of procedure should we apply, or do we leave it to the individuals to sort it out.One thing is clear though: there needs to be someone who has specific coordination responsibility for the function. As is her way, Irene has volunteered to take on the role, but in a very limited manner only, pending the appointment of a permanent jobholder.

The Committee is also considering several other similar issues as well.As commented previously, I would like to see us this year coming to grips with several proposed structural and administration issues, which would allow NSAS to operate to maximum efficiency. Outreach is just one such issue.

In recent months there has been a noticeable fall away in attendance at the Theory Group meetings. There will be different reasons for this, not least of which is that the current format of using DVDs has not always worked well with the Regis Hall AV equipment.It has been a matter of discussion for some time and, at the March General Meeting, it was proposed and agreed that the Theory Group should go into recess for three months, pending resolution of a future program.As a major part of that resolution, there will need to be an individual who puts his/her hand up to be the coordinator of the

Group. There may be a group emerge who will look after this function, but there must still be a project manager who will co-ordinate the whole function.Accordingly, the theory group is now in recess for April, May and June.

A message that comes across pretty strongly here is that we need to improve our participation.We need more involvement from the membership to spread the workload as the past practice of reliance on a very small number of highly competent individuals to do the bulk of the work is not a good way to go.When you consider the nature of what we do and the time and equipment involved, NSAS needs quite a bit of on-the-ground project management and admin input.

Lastly, it had been thought that for cost reasons, this would be the last Reflections that would be distributed by post, which would save on the print and postage expenses.The process is not complete as yet and must in any event be approved at a General Meeting. Assuming the proposal is approved, all Members will receive future Reflections via email only.Should there be a particular need for a printed copy to be posted, this will be done.

See you soon, and hello to our new members and visitors.

Bruce Retallick

General Meetings: April 16th Speaker: Dr... Mark Philips - The Magellan Telescope and Type 1A supernovae May 21st Speaker: Ivy Wong (CSIRO) - The Galaxy Zoo project

June 18th Speaker: Glen Rees (CSIRO) - Brane world cosmology

Theory Group Meetings: Recess until July 2013

NAG Meetings: April 23rd Finding your way around the night sky May 28th Practical observing (May be postponed depending on the weather) June 25th Types of objects

Observing Nights: Consult NSAS’ web site at http://nsas.org.au/observing/

Deadline: Please send your contributions to the July issue of Reflections in time to reach the editor before June 15th to nsas.editor@ozemail.com.au

Calendar

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Do the heat and humidity of Sydney in January get you down? You could

avoid it by travelling to the Arctic, seeking the Northern Lights. That’s what twenty three people, mostly from Australia, did this year, ably led by Fred Watson and Marnie Ogg, travel consultant extraordinaire.

The tour began on January 8th in Stockholm with a brief view of the Ericsson Globe, which represents the Sun in the largest scale model (1:20 million) of the Solar system. At the Nobel Museum we received the first of many entertaining talks by Fred, this about Brian Schmidt and his work that led to the award of the 2011 Nobel Prize in Physics.

A p p r o x i m a t e l y half way between Stockholm and Uppsala is the K v i s t a b e r g Observatory, no longer an active research facility but a museum. A colleague of Fred’s, Professor Bertil Pettersen, introduced us to the observatory and its instruments, the largest a Schmidt telescope with a 135cm primary mirror, very similar to the UK Schmidt at Siding Spring.The observatory exists because of a donation made to Uppsala University in 1944 by

Astronomy on the RunNils Tamm, a landscape artist and experienced amateur astronomer who studied variable stars and discovered several novae in the 1920s and 30s.He was a skilled photographer and also produced beautiful paintings of planets, especially Mars, copies of which were on display in his private observatory.Tamm, who died in 1957, has the distinction of having a minor planet, Nilstamm named after him. He now rests inside the concrete pillar that supports his 13cm Zeiss refractor telescope.

Skokloster Castle, also between Stockholm and Uppsala and on the shore of Lake Malaren, was built

between 1654 and 1676 for a wealthy military commander count Carl Gustaf Wrangel.When he died in 1676, the money ran out, work stopped and the dining hall is still unfinished. The castle does, however, house some treasures including two telescopes made by Johannes Wiesel (1583-1662), state of the art instruments with five lenses.Following the count’s death, in an interesting astronomical twist, Skokloster Castle came into the hands of the Brahe family because Wrangel’s elder daughter had married into that line.There are portraits of the great astronomer in the castle.

Nine hundred and fifty kilometres north of Stockholm is Kiruna; less light, more snow. Despite its name, the Ice Hotel at Jukkasjarvi, 17km from Kiruna, has warm rooms; you don’t have to sleep on blocks of ice from the Torne River.What it does have in abundance is snow

Aurora over Jukkasjarvi (Sweden)

Aurora over Kilpisjarvi (Finland)

and, in January, long nights and, if the sky is clear, great conditions for viewing the Northern Lights.On our first night there was no aurora but, for those prepared to stand around in snow at -16°C, Fred Watson gave a tour of the northern constellations.Our education continued the next morning when we visited the Swedish Institute of Space Physics (IRF) at Kiruna. The institute, established in 1957 by the Swedish Academy of Sciences, conducts research in atmospheric physics, space

physics and space technology.It has a significant postgraduate training program and collaborates in several large international projects using satellites and ground-based equipment.There are IRF instruments in satellites orbiting Venus, Earth, Mars and Saturn. Dr.. Lars Eliasson, the director of IRF, took us around the institute and spoke enthusiastically about the research programs in atmospheric physics.He also gave a presentation on the physics of auroras. A timely one, because, that evening, just after everyone had gone to bed expecting to sleep, the hotel reception rang at 10.30pm with the call to arms `AURORA’.On with the warm clothes and outside with the camera and tripod.The light show started as small patches of green in the west and progressively spread to the northern sky with large, moving green curtains tinged with red, before fading out around midnight.That’s what we’d come to see and we hoped it would not be the last appearance of the Tricky Lady.

The next evening we were on the Norwegian coast at Narvik where, after dinner, we were regaled, in typical Fred

Watson fashion, with a talk that covered just about everything to do with the universe; relativity, gravitational lensing, dark matter and dark energy.That gave us plenty to mull over while we travelled north the next day but, in reality, the beauty of the Norwegian coast distracted any but the most fanatical cosmologists in the group.

By this time, however, a serious issue had arisen, the fire at Coonabarabran.Our tour was called `Fire in the Sky’, but back home it was fire on the ground that was attracting attention, especially that of Fred Watson whose friends and colleagues, home and workplace were all at risk. Fortunately, as we now know, through the work of the Rural Fire Service and SES, disaster was averted.

As if to calm our nerves, the aurora made a brief appearance at Malangen Brygger, our first stop on the way north.

The brilliant but somewhat eccentric Norwegian scientist Kristian Birkeland was first to propose a mechanism that explained the occurrence of auroras that is essentially similar to our present understanding.Although his colleagues in Northern Europe accepted his explanation, it was rejected elsewhere, especially in England and it was only with the confirmation of the existence of the solar wind by space

probes that Birkeland was vindicated.At the University Museum in Tromso there is an excellent exhibit dealing with Birkeland’s research, including a working model of his Terrella, a large vacuum chamber in which he produced artificial Northern Lights.

Because of cloud at Tromso, our next encounter with the aurora occurred across the border in Finland at Kilpisjarvi.If you want to view the aurora you have to be prepared to travel. At Alta, on our last evening in Northern Norway, magnetic field activity was strong, our hopes were

high but the clouds were low and we had a `no show’.

From Norway we flew to Iceland and, although we did see the aurora there briefly

on two occasions, that part of the tour was more about the geology of Iceland, especially the volcanoes and mid-Atlantic rift.

For some of us the culmination of the tour occurred when we returned to Copenhagen and visited the island of Hven, the site of Tycho Brahe’s Uraniborg Castle and Stärneborg observatory.The museum, which houses replicas of some of Tycho’s most important observing instruments including the Great Quadrant, is situated in the former All Saints Church. On the site of Stärneborg, where the original foundations of the underground observatory survive, there is a multimedia display that simulates an evening’s observation with the master.The following day we visited Kronborg Castle (Hamlet’s Castle), completed by Frederik II, Tycho’s patron, and Frederiksborg Castle, started by Frederik II but completed by Christian IV who withdrew royal support and, consequently, was responsible for Tycho moving to Prague where his collaboration with Kepler began.

After a final group dinner in Copenhagen, the tour wound up on January 26th with a visit to the Round Tower observatory and a chance to view books written by Galileo and Tycho Brahe, two men who continue to inspire after four hundred years.

John WalkerAll photos by the Author

Tycho Brahe Museum with replica of his sextant

Tycho Brahe statue, Hven

Tycho Brahe’s great quadrant

Believe it or not, this is Astronomy …well, not all of it … and not all the

time so relax.

With so much information available these days, it is hardly pardonable to think that solar eclipses can only occur when the Moon is exactly at new phase when it is exactly at one of its nodes with the ecliptic when the Sun is precisely on the line of nodes.

See Diagram 1. This line joins the two points, called nodes, where the Moon’s orbit passes through the plane of the ecliptic , i.e. the plane of Earth’s orbit. Up-to-date definitions include such additional phrases as ‘or close to the line of nodes’ etc.

The Moon’s angular diameter, see Diagram 2, ranges from 29’23” (0.48976 degrees) at apogee to 33’29” (0.55806 degrees) at perigee. For a solar eclipse to occur, the Moon’s variable disc must intersect the ecliptic.

The Wi(l)der the Shot, the More Interesting is the Result... What pastime is that?

Diagram 3 shows that a perigee Moon selects a longer, and symmetrical, portion of the Sun’s apparent orbit as host for an inevitable eclipse. The double portion of the orbit is known as an “eclipse season”. An apogee moon will result in a shorter season. For the limits of the seasons,

Diagram 3 shows that they occur when one half of the Moon’s angular diameter just fills the gap between the ecliptic and the Moon’s orbit.

T h e smaller limit is about 15 degrees from the line of nodes and the larger limit is about

17.5 degrees from the line of nodes. These apply on both sides of the line of nodes so the region for inevitable solar eclipses is as small as about 30 degrees and as big as about 35 degrees.

Let us look at the two planes edge-on when the Moon is furthest from the ecliptic, i.e. half way between successive nodes. Diagram 4 (opposite page) shows that the maximum angular distance between ecliptic and the Moon’s orbit is about ten times the Moon’s angular diameter – about twenty times its value at the limits of an eclipse season.

An important question demands attention: “How long does it take the Sun to cover such arcs of its apparent orbit around the Celestial Sphere ?” The Sun’s average apparent angular velocity is 360 degrees in 365.26 days or nearly 0.986 degrees per day. At this rate, the Sun could be anywhere in a 35 day span – the longest possible “eclipse season” - when the New Moon is at one of its nodes.The shortest possible eclipse season is a bit more than 30 days. Even this shortest ‘season’ is longer than a lunation at 29.54 days so there must be a solar eclipse at every nodal vicinity. Moreover, the longer ‘seasons’ could easily host two solar

Diagram 2:The small angle is the “angular diameter” of the Moon as viewed by an Earth-bound observer.The actual size varies around the value 31 arc minutes

Diagram 1:The outer closed curve represents the apparent orbit of the Sun as it appears to Earth-bound observers so its plane is the ecliptic.The inner curve represents the orbit of the Moon about the Earth, E, whose position is the central dot.The orbit of the Moon is partly shown as a broken line representing that part of the orbit which is below the ecliptic.The nodes are the points at which the Moon passes through the ecliptic, one being the ascending node A and the other being the descending node D. The line through these two points is called the line of nodes. Currently, the Sun crosses the line of nodes in May and November.

Diagram 3:Limits of “eclipse seasons”.The inner pair of circles represents the Moon near apogee and the outer pair the Moon near perigee.N is the node, m the Moon path and e the ecliptic.

Diagram 4:Imagine a viewer on the line of nodes. From such a position, the ecliptic [solid line] and the plane of the Moon’s orbit [bracketed part of the upper ray] would be edge-on. The broken line continues the Moon’s plane to the Celestial sphere. The angle between the lines equals the inclination to the ecliptic of the Moon’s orbit. The arc joining the ends of these lines subtends an angle at the line of nodes roughly ten times the Moon’s angular diameter. The number can be anywhere from 9.22 to 10.5. We see, from Diagram 3, that an eclipse season would begin when the separation of the two orbits reduces to half of the Moon’s angular diameter and would continue till the separation increases to half the Moon’s angular diameter on the other side of the node where the apparent distance between the orbital planes subtends, at the earth, an angle equal to half the Moon’s angular diameter as seen from Earth.

eclipses: one before and one after the Sun passes the line of nodes so about a lunation apart.

A surprise result of having solar eclipses at both New Moons in a season is that, in between them, there is an excellent chance that the alignment of Sun, Earth and Moon will be good enough that a lunar eclipse occurs at the intervening Full Moon. Hence there could be a total of two solar eclipses and one lunar eclipse in one eclipse season. Clearly, the triple situation is much more likely if the two solar eclipses occur when the Moon is near perigee. The areas of visibility of triple eclipses are quite different.

The first astronomy reference book that I ever bought was written in Czechoslovakia and translated into English. It has a Northern Hemisphere bias and especially Northern Hemisphere dates. Included in the impressive ‘back matter’ are year-by-year details of eclipse dates (except for penumbral lunar eclipses) for the 22 years from 1979 to 2000 and that 1982 had a total of 7 eclipses and that 2000 had a total of 6 eclipses.

Quoting dates of triple eclipse seasons in those two years:

Solar on 21 June, Lunar on 1982 06 July, Solar on 20 July (See footnote) Solar on 01 July, Lunar on 16 2000 July, Solar on 31 July

The vertical pairs of dates are 18 years plus a few days apart. The Chaldean astronomers working in Mesopotamia in the 8th and 7th centuries BCE had already discovered that many lunar conditions repeated after

223 lunations which, with modern measurements, become about “18 years,11 days and 8 hours” or about “ 18 years,10 days and 8 hours” depending on the number of leap days added. This special time interval is an important consideration in predicting eclipses into the future.

That old reference book confirms that there are always at least two solar eclipses in a calendar year, that the times of the eclipses keep moving towards the beginning of the year – a consequence of the changing direction of the line of nodes - and that successive solar eclipses are mostly 6 lunations apart but being interrupted by triple eclipse seasons. The results for 22 years suggest that solar eclipses outnumber lunar ones by a ratio of about 50 to 34. Also that the most common annual result is 2 solar and 2 lunar with members of mixed pairs being separated by half lunations.

Footnote: For those who might think that Northern Hemisphere dates distort the annual picture for we Southerners, there is not one occurrence of interest on the first or last day of any of the 22 years covered and any difference between calendar dates for the same occurrence can only be one day. Hence, any conclusions drawn by me are unaffected.

Bob Roeth

Reference: Back matter of ‘The Amateur Astronomer’ by Antonin RuklCopyright Octopus Books (Prague 1979)

The Binocular and Telescope Shop84 Wentworth Park RoadGlebe NSW 2037Phone: (02) 9518 7255www.bintelshop.com.au

Paul’s CornerI am wondering how many of you got

to see this event and I can report that I myself had a bit of success despite the numerous trees in this HKG retirement village which does have so many lovely gardens, one of the reasons I chose to move to here.

But those trees are a menace when trying to follow astro events, so I gave up moving the telescope every few moments as the Moon wandered behind the foliage.

I am quite happy and chuffed that it seems to have captured an extra item that had me perplexed.

Careful study of “Starry Night” for any other bright stars in that area of sky and some manipulation of the lightness and contrast have proved that indeed I have managed to image the Ganymede, one of Jupiter’s moon, with my hand held Canon 20x optical zoom lens!

Added to that I have another image taken later that shows that object further around its circular orbit around Jupiter, somewhat closer to the Moon, and that matches up with Starry Night too.I am now enthused about my new digital Camera.

Paul Shallow

PS I did make some rather rash statements about my new camera getting an image of Ganymede but now on finding some

old photographs in a box in my garage storage I find that I did just that many years ago, no problems, as I had been lent a 500mm lens for my old SLR camera and have all 4 moons as pinpoints on some photographs. I think that at that stage I was just too keen to record that Jupiter’s storm, the pink/red spot, and did not consider other things I had photographed,Oh the excitement of all the new things you can do in the enthusiasm of a new hobby!

Moon/Jupiter Conjunction

Jupiter and Ganymede

A Successful CampaignAs our club is always trying to recruit

new members, Peter Korber was quick to seize on the opportunity offered to him to have an advertorial run in the a couple of local newspapers.

After some discussion, it was decided that Peter would meet Danielle Nicastri and Cameron Richardson, her photographer, for a photo shoot on Monday March 18th.where they would be joined by Bruce Retallick and Bob Fuller.

The article was published the same week in the Northshore Time, the Manly Daily and the Mosman Daily and, as a result, 15 guests turned up the following Tuesday for the inaugural NAG session.

Many thanks to Peter for this successful recruitment campaign.

For centuries, every country had used a different prime meridian but, with the development of international trade, it became clear in the 1800s that a common system that would facilitate trade and relations between countries was crucial.

In 1884, 25 nations met in Washington for the International Meridian Conference.The choice was pretty much limited to the Greenwich and the Paris meridians and the battle between France and the United Kingdom got rough.France wanted the Paris meridian because it was the French who had calculated the length of the meridian. But the British had arguably the best nautical charts all based on the Greenwich meridian.

The French delegation then proposed to adopt a “neutral” meridian, neither French nor British, on El Hierro, an island in the Canary, since nicknamed Isla del Meridiano (the “Meridian Island”). But that would have required the construction of an observatory and to connect it via telegraph to the continent.

The British delegation proposed to adopt the Greenwich meridian and, in return, they declared they would be ready to accept the French metric system as the international system.

Most countries supported this proposal.

Only Brazil, the Dominican Republic and France voted for the El Hiero meridian!The Greenwich meridian was therefore adopted as the Prime Meridian.Ultimately, all countries would join the Greenwich-based system in 1911.

The Greenwich meridian had been marked by a brass strip in the Observatory courtyard but has been upgraded to stainless steel and, since 16 December 1999, it is marked by a powerful green laser shining north.

Today, the meridian of Greenwich is still used as the Prime Meridian but I’m told that the metric system is still not used on all British roads!

Jean-Luc Gaubicher

Note: The meridian of zero longitude in the World Geodetic System 84 that is used in cartography and in GPS systems in particular, is 102.5metres east of the Greenwich meridian at the latitude of the Greenwich Observatory.

Jean-Luc GaubicherSources: various, including Wikipedia

The Battle of the Meridian

The Paris Meridian in the Salle MéridienneObservatoire de ParisPicture wikimedia.org

Prime meridian at the Royal Observatory GreenwichPicture wikimedia.org

Laser beam marking the Prime MeridianPicture wikimedia.org

On March 21st, the ESA Planck team released their latest map of the cosmic

microwave background (CMB).This highest-precision map yet pins down key parameters of the Universe today.One of the most important results is that it reveals that the universe is expanding slightly more slowly than had been thought.This implicates that the amount of dark energy represents only 68.3% of the Universe and therefore, the quantity of visible matter being well established, that there is a little more dark matter (27%).

Another consequence is that the Universe is a tiny bit older by a few tens of millions year than previously thought.

Planck Tweaks Universe ParametersPlanck Space TelescopePicture ESA

Planck’s latest CMB mapPicture ESA

So, did you find it? If not, here it is:

And that was an easy one.

Graph 4 is a bit trickier: a potential candidate has been identified but not confirmed at Day 26.5.

As of today Planet Hunters has submitted one scientific paper for a “circumbinary planet in a four star system” and is waiting for its acceptance.

So if you are ready for the challenge and don’t know what to do in the coming winter evenings, join the hunt for planets, your name could well be associated with the discovery of a new planet

Jean-Luc GaubicherLight curves courtesy of planethunters.org

Reflections is published quarterly by the Northern Sydney Astronomical Society IncPO Box 56 Lane Cove 1595 Tel: 0423 971 374 E-mail: nsas@nsas.org.au Web site: www.nsas.org.au

Feel too old for an Easter egg hunt?So, what about a planet hunt?

If you did not attend our March general meeting, you missed a very interesting, and straightforward, talk by Dr... Joao Benton.Joao is a post-doc Research Fellow at Macquarie University and he is mainly involved with SuperWASP.

The Super Wide Angle Search for Planets program is looking for exoplanets using the transit method.So as to cover both hemispheres, Super WASP is operating from 2 sites, one on La Palma, one of the Canary Islands, and the other in South Africa.

So far, nothing extraordinary but what’s different from other astronomy projects is that its equipment is comparatively dirt-cheap as it is built from pieces that are readily available to amateur astronomers.Each observatory consists of an array of 8 Canon 200mm f/1.8 lenses. As these lenses were no longer in production some of them had to be bought on E-bay!(Yes, I’ve checked and there are still a few of these lenses for grab around the $3,500 mark.)These lenses are fitted with 2048x2048 CCD cameras that are, according to Joao, the most expensive part of the set-up but, overall, any (well-off...) amateur could build a comparable observatory or, at least, a 1-lens system..

Are You Ready to Go on a Planet Hunt?Joao went on mentioning that they have actually used data provided by such an amateur astronomer.

So, maybe you don’t have the budget to build your own observatory, or you only have a small backyard and your better half is not willing to give up their rotary hoist clothes line…Don’t fret; you can still be part of this exciting hunt by joining the Planet Hunters project (http://www.planethunters.org).

This project is part of Zooniverse.It uses data from NASA’s Kepler telescope and asks for the public to help analyse light curves and find planets that computer programs may miss.

Easy, yes? Well not quite.Graph 1 shows a highly idealized light curve as presented to illustrate the theory behind the transit method of detection.

Now have a look at Graph 2: this is a typical light curve you will be presented with… Can you find a potential transit?

Super Wasp settingPhoto courtesy of superwasp.org

Graph 4

Graph 1 courtesy of superwasp.org

Graph 2