MEETINGS

SEPTEMBER MEETING

        Phil Berry opened the September meeting which was a change of programme.  The title of the evening was “Aspects of Observation” consisting of talks from members about different methods of observing both day and night skies, followed by an introduction to setting up a telescope from scratch.

        Phil introduced the first talk of the evening and told members that the speaker, our Director of Observations, had recently been awarded a Fellowship of the Royal Astronomical Society for his work in Occultation Observations for which we heartily congratulate him.

Occultation Observing for Amateurs

Brian Mills

        Earlier this year, Brian organised a Society first; - an observation of a grazing occultation by the moon.  His talk was an explanation and introduction for all members.

        What is an occultation?  Brian began by explaining the general meaning of ‘occultation’ – where a body is concealed from view by another.  If the object passing in front is smaller than the main object, then it is called a ‘transit’ such as the transit of Mercury or Venus.  But if the objects are of similar apparent size, then we call it an ‘eclipse’.

        Examples of occultations are when the moon passes in front of a much smaller object and here Brian showed an image he himself took a few years ago of Venus about to be occulted by the unlit side of the moon as the moon passed in front.

        Planets can occult stars and Brian mentioned that the last one visible was in 1984 and the next will be in 2015, so they are quite rare.

        Even planets occulting planets.  In 1815, Venus occulted Jupiter and Brian said this will occur again in 2065; worth waiting for…

        Using airborne observatories professional astronomers have determined atmospheres around Titan and Pluto and rings around Uranus using occultation methods.

        Asteroids can occult stars and on one occasion, by combining accurate timings taken by many amateurs, the shape of Asteroid Tercidina was able to be determined.  Brian showed the remarkable results, giving the shape of the asteroid in the form of all the timing lines being plotted in their relative positions.

        Brian then went on to say around the Ecliptic is a band called the Zodiacal Band in which lie stars likely to be occulted at some time.

        An image showed an example of a star about to be occulted by the moon’s unlit rim – the easiest lunar occultation to be accurately observed, particularly by a waxing moon when there is likely to be Earth shine as can be seen in the following image.

          Regulus about to be occulted in 1999

      An exiting (emerging) star is much more difficult to observe accurately, but Brian described how this could be predicted more accurately using position angles.

        Why observe occultations?  Accurate timings by amateurs provide information on determining shape and motion of the moon.  It also helps define the precession of the Earth’s pole which takes 26,000 years to make one complete rotation and as Brian said, at the end of the next 26,000 years, Polaris will once again be the Earth’s pole star.

        Unknown double stars have been identified.  Since the moon has no atmosphere, an observed star should disappear abruptly behind the limb of the moon.  There have been occasions when the occulted star has disappeared with a step in its brightness, suggesting there may be a very close double star.

        The next occultation Brian talked about was a Grazing occultation where an observed star just scrapes along the rim of the moon.  Since the star is so far away, the projected silhouette of the moon onto the Earth’s surface is virtually the same size and shape as the actual edge of the moon.  This is such a well defined ‘shadow’ on the Earth, that two observations made only a short distance apart could result in one seeing a short but total occultation and the other not seeing any occultation at all.

        But Brian stressed the importance of any observations taken between these points as they may well see the star winking in and out; incredibly though it may seem, they are looking through gaps between the lunar mountains on the moon’s rim.

        As mentioned earlier, Brian arranged for members of the Society to observe from six locations in a line down a country lane near Bewl Water; along a mean graze-line perpendicular to the motion of the moon’s silhouette.

        By taking accurate timings, between them they ended up with a series of measurements representing that part of the silhouette of the moon’s mountains.  One observing point saw no change in the brightness of the star and this disappointing observation to the members there, was very important because it showed the limit of the height of the mountains.

        This data is now sent off to the International Occultation Timing Association for analysis.

        Brian spent some time describing how the timings are made as accurately as possible, even to adjusting the results with what is known as one’s Personal Equation; a measurement of a person’s speed of response, having been determined by reaction tests available on the Internet.

        It is through Brian’s dedicated observations of occultations over many years that he has been recognised by the RAS.

Observing the Sun

Geoff Rathbone

        Since moving into my house, the M25, M26 and M20 motorways have been built, leaving me in the middle of a sky-polluting triangle, both by light and particles.  The charming trees of thirty years ago now leave me looking up at the night sky through a virtual funnel.  I had always had an interest in our Sun, so didn’t find it too hard to abandon my night sky observations and begin to observe our nearest star more seriously.

        Firstly, looking directly at the Sun with the naked eye is extremely dangerous but there are so many other ways of looking at different aspects of the Sun.

        Projection is the easiest and enables a number of people to view the image at the same time.  Even a pair of mounted binoculars with an eyepiece poking through a hole into a cardboard box projects a good enough image of the Sun onto the opposite face.  The bigger the box, the larger the image.

An example of an off-set Baader solar filter in front of the corrector lens of a Schmidt Cassegrain

        I have added a Baader Solar filter to the front of my faithful 11-inch Celestron Schmidt Cassegrain.  This filter reduces the light from the sun by about 10,000:1 and positioning the Baader filter over a three-inch off-set hole in a cover in front of the correcting lens reduces the light even more.

        I use the finder scope to project the Sun onto a card behind its eyepiece to line the telescope up with the Sun, but avoiding looking through the finder eyepiece at all costs.

        When following the formation of sun-spots over a period of an hour or so means that the telescope must be made to track the Sun and the Sun appears to move from east to west at a different rate to the background stars, so I have to use the Solar tracking rate on my tracking control unit.

        Observing sun-spots reveals a lot about the Sun; for one thing it is possible to see the different rates of rotation of the Sun between its equator at 25 days and the rotation at the poles at about 34 days.  Also the Suns axis as seen from Earth changes over the year due to the plane of our orbit.  There are charts that can be downloaded from the Internet which enable sun-spots to be plotted, taking this seasonal change into account.

        Another way of observing the Sun is by using a spectrometer to identify the absorption lines in the spectrum.  There are a number of kits on the market one can make up, using an interference grating and graduated scale.  Even looking at the clouds on a bright day it is possible to identify the Sodium, Hydrogen and Calcium lines; these being the most obvious.

        One of the best and most enjoyable ways of observing the Sun by the amateur is by using a PST (Personal Solar Telescope), enabling one to observe the Sun in hydrogen-alpha light.  Regrettably, they do cost around £500.

        The telescope incorporates a tuneable Etalon filter, allowing the observing to look at prominences at the edge of the viewable Sun or by slight adjustment of the filter, to see the structure of the surface of the Sun and the turbulent area around sun-spots.

        I have witnessed the formation of sun-spots; first appearing as one, and then watching a bright link stretching out to form the second, as they nearly always occur in pairs.

        It is also possible to observe the Sun in Calcium light and see yet more aspects of the Sun, but as Phil Berry pointed out, they are expensive telescopes to buy and it is important to make sure that the a Calcium telescopes works for your eyes as in some cases, amateurs have been very disappointed particularly with older eyes.  It still works for me – for now!

Setting up a telescope from scratch

Phil Berry

        Using the Society’s own 4-inch refracting Konus telescope with an un-driven equatorial mount, Phil began his introduction to setting up an astronomical telescope from scratch by beginning with just the mount on the tripod.

        He said at a recent observing session there had been a little confusion in setting up a telescope in daylight and it was worth going though the basic assembly and line-up in advance of future sessions.

        He then described the components; the sturdy tripod, the equatorial mount, the telescope tube and the finder scope and balance weights.

        The tripod usually has a tray that fits between the legs, giving the tripod good rigidity and Phil said that it is best to line one of the legs to the south which will help during the line up procedure.  Also, the height of the legs should be adjusted at this time for the kind of telescope being used, so that the eyepiece will end up at a convenient height during the observing session.

        The top of the tripod must be levelled using a spirit level of which there are a number of small ones available.

        The feet of the tripod should now be firmly anchored.

        Next, the equatorial head is mounted on top of the tripod.  If not previously set, the latitude angle of the observing site should be adjusted on the latitude scale; in our case this is 51o North.  The mount is now aligned so that the axis points towards the north. 

        During daylight, this can only be approximate.  Once the stars are visible, the two stars called the ‘pointing stars’ at the rear of the “Plough” in the Great Bear point to Polaris and the axis of the equatorial mount is made to line up with it.  In most cases this is sufficient for short term observing such as an occultation. But if long exposures are to be made, then the axis needs to be more accurately aligned and Phil showed how a polar-alignment tool is used.  This fits in the centre of the axis of the equatorial mount and using an illuminated graticule, the mount is aligned to the true north pole axis relative to Polaris and other fainter stars.

The polar alignment tool is inserted through the middle of the mount

       Back to daylight.  The weight bar and weights are attached to the mount ready for the body of the telescope to be clamped into position in its cradle.  With the finder telescope and eyepiece in approximate position, Phil now showed how the assembly is balanced so that when any Right Ascension and Declination locking rings are loosened, the telescope remains in balance.

        Finally the finder scope is roughly set on something like a distant television aerial so that the main telescope is looking at the same object.

        Once the stars become visible, final adjustments can be made to the finder scope using a star.  This now reduces the parallax as much as possible.

        The telescope is now polar aligned for a night’s observing.

OCTOBER MEETING

        Wednesday 19th October 2011 –Brian Mills gives a talk he calls “Point Granny’s Box Brownie at the Stars”; a practical approach to imaging the sky, even with an un-driven camera.  The talk includes a basic introduction to “Registax”, the free Internet programme.

        Meetings begin at 1930 although members are invited to arrive anytime after 1900 as this is a good time to exchange ideas and discuss problems and relax before the meeting.

        The venue as always is held in the Upper Room of the Methodist Church at the east end of Wadhurst Lower High Street, opposite the entrance to Uplands College.  (For those with SatNav – the post code is TN5  6AT)

        Anyone is welcome.  Non-members are asked to contribute £2.

FUTURE  MEETINGS

        Wednesday 16th November 2011 – David Mannion talks to us about “Galileo and 400 Years of Telescopic Astronomy”.  David has three degrees in Astronomy and has been a teacher for 24 years.  He is also co-writer of a book of the same title as his talk to us tonight.

        Wednesday 14th December 2011 – This is our Christmas meeting when Paul Treadaway will present a talk called “The Theory of Relativity”.  Paul is one of our own members and has spoken on a number of topics before.

        There will also be mince pies to have with coffee or tea.

        Wednesday 18th January 2012 – January is the month when we hold the Society’s Annual General Meeting.  This is then followed by a talk by Dr. Bob Seaney called “The Multiverse Universe” during which Bob introduces us to an exciting look at the Universe.

OTHER NOTES AND INFORMATION

FEDERATION OF ASTRONOMICAL SOCIETIES

ANNUAL CONVENTION & AGM

        The Annual Convention of the Federation of Astronomical Societies, which we all belong to, is holding their annual convention and AGM at the Institute of Astronomy, Madingley Road, Cambridge CB3 0HA on Saturday 15th of October 2011.

        There are talks on X-ray Astronomy, Active Galactic Nuclei, Photographing the Night Sky, and Planetary Nebulae.  The Astronomer Royal, Lord Martin Rees will also be present.

        There will also be Trade Stands, Exhibitions and Telescope Tours.

        The cost is £5.00 on the door which opens at 0900 with the lectures commencing at 1000.

        More information can be found at: www.fedastro.org.uk/

SKY NOTES FOR OCTOBER

Planets

Mercury passed through superior conjunction on 28th September and is therefore unobservable this month from the UK .

Venus suffered a superior conjunction on August 16th and so will not be visible until late November or early December.

Mars is a morning object rising at around 01.00 hrs throughout the month. By mid-month it is more than 40° high in the constellation of Cancer by sunrise. During the second half of the month it moves eastwards into Leo.

Jupiter is set to be the real jewel in the winter evening skies. At the start of the month it rises around 1930 (BST) but by the end of the month this has become 16.30 (GMT). On the 29th it reaches opposition - the moment when it is exactly opposite the Sun - and is on view all night (in the constellation of Aries) at magnitude -2.9. At this brightness there can be no mistaking it above the eastern horizon, with the Moon very close by on the 13th.

Saturn is in conjunction with the Sun on the 13th of the month and is therefore invisible to us. However, it will re-appear as a morning object in the second half of November.

Lunar Occultations

In the table below I’ve only listed events for stars down to magnitude 7.0 that occur before midnight although there are others that are either of fainter stars or occur at more unsociable hours.  DD = disappearance at the dark limb.

Times are in BST except for the last one.

Oct.

Time

Star

Mag.

Ph

PA °

2nd

1901

SAO 185357

6.7

DD

136

7th

1940

SAO 145698

6.5

DD

91

8th

2052

Kappa Aquarii

5.0

DD

102

30th

1755

SAO 186135

5.7

DD

63

 

Next

event in GMT

     

31st

1606

SAO187504

3.5

DD

66

Phases of the Moon for October

First ¼

Full

Last ¼

New

4th

12th

20th

26th

ISS

Below are details of the passes of the ISS that occur before midnight as seen from Wadhurst and are magnitude -3.0 or brighter. The details of all passes including those visible from other areas can be found at:

www.heavens-above.com

Please remember that the times and directions shown below are for when the ISS is at it’s maximum elevation, so you should go and look a few minutes before. Times are in BST apart from the last two.

Oct.

Mag

Time

Alt°

Az.

20th

-3.0

1932

44

SSE

22nd

-3.3

1908

60

SSE

23rd

-3.5

1944

84

N

24th

-3.4

1844

76

SSE

25th

-3.5

1920

78

N

26th

-3.4

1820

90

NNW

26th

-3.0

1955

58

WNW

27th

-3.5

1856

78

N

28th

-3.5

1756

79

NNE

28th

-3.4

1932

79

SW

29th

-3.5

1831

82

N

Next

two

passes

are

GMT

30th

-3.2

1807

65

SSW

31st

-3.4

1707

88

SSW

Iridium Flares

The flares that I’ve listed are magnitude -3 or brighter although there are a lot more that are fainter, occur after midnight or at a lower altitude. If you wish to see a complete list, or obtain timings for somewhere other than Wadhurst, go to: www.heavens-above.com

Remember that when one of these events is due it is sometimes possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time.  Times are in BST apart from the last one.

Oct.

Time

Mag

Alt°

Az.

5th

2036

-8

49

ESE

6th

1854

-3

55

S

6th

2030

-4

49

ESE

11th

1833

-3

50

S

11th

2009

-5

51

SE

12th

1827

-4

49

S

17th

1941

-7

50

SE

23rd

1914

-4

48

SSE

28th

1953

-4

46

S

Next

flare

time

is in

GMT

31st

1729

-5

11

WNW

Meteors

The Draconids - This shower is active from October 6th to the 10th with maximum occurring on the evening of the 8th. It normally produces a few meteors per hour, but this year there is the chance of something much better, although earlier “storm” predictions are now being played down. Due to the relationship between the Earth and the dust trails left behind by successive passes of the comet, there is a suggestion that at maximum we could see a ZHR up in the high hundreds. This is a notoriously difficult shower to predict, as in the past estimates have been wide of the mark. On the night of the 8th it would be wise to check as soon as dusk falls because any peak that occurs could be very short, although the latest suggestion is that it may occur from 2000 to 2200. The radiant is shown on the map by a red cross. However, meteors could appear across a wide area of sky so it would be unwise to concentrate solely on this area. It would be best to look generally north and, if possible, shield yourself from the Moon that will be in the south at an altitude of 35° by 2200. Meteors from this shower are extremely slow moving.

The Orionids - The normal limits for this shower are from October 16th to the 30th with a broad maximum that stretches from the 20th to the 22nd when the ZHR will be around 25. These are fast meteors that very often leave ionised trains. On the night of maximum the radiant rises at 2200 BST.

The Night Sky in October (Written for 2200 BST mid month)

In the north Ursa Major is not only on the meridian but is also at its closest to the horizon that it can get from these latitudes. Also on the meridian but on the opposite side of the celestial pole is the constellation of Cepheus that lies close to the zenith. Cassiopeia and Draco are both well positioned with the latter currently easy to identify as it winds its way amongst the “Bears”.

Looking east the sky is dominated by the brilliant Jupiter, already some 30° above the horizon. Binoculars, if they can be tripod mounted or rested on a sturdy support, will show the four Galilean moons. The diagram shows, for example, their appearance on 15th October at 2200 BST.

If we now look towards the south we see that Pegasus is almost on the meridian, which means the magnitude one star Fomalhaut (the brightest star in Piscis Austrinus) will be visible close to the southern horizon. The best way to locate it is to draw an imaginary line down the western side of the square of Pegasus and curve it slightly to the right. Fomalhaut has a planetary companion that was the first to be discovered visually when it was imaged by the Hubble Space Telescope in 2004 and 2006.

Pegasus has a retinue of small constellations plus the larger Pisces that fills an area to the south. To the north is Lacerta, to the east Triangulum and Aries and to the west Vulpecula, Sagitta, Delphinus and Equuleus.

To the west of the sky the Summer Triangle is still prominent with Deneb at an altitude of around 70°. Hercules is visible but Corona Borealis will soon be lost to view.

Reminder

Don’t forget that BST ends and GMT begins on Sunday 30th October at 0200 BST.

LIST OF USEFUL WEBSITES

Useful Web-sites

Provided by Brian Mills

http://stargazerslounge.com/   Provides a resource for exchanging astronomical information and has a discussion forum for a wide range of astro topics. They also have a “for sale” area.

http://www.astrobuysell.com/uk/   Site for buying and selling used astro gear

http://britastro.org/baa/   The British Astronomical Association

http://www.popastro.com/   The Society for Popular Astronomy

http://www.iankingimaging.com/   Our own Ian King’s site for all astro equipment

http://apod.nasa.gov/apod/astropix.html   The site for  the “Astronomy Picture of the Day”

http://apod.nasa.gov/apod/archivepix.html   Huge archive of the “Astronomy Picture of the Day”

http://www.astronomie.be/registax/   Registax, the free stacking software for astro images.

http://deepskystacker.free.fr/english/index.html   Deep Sky Stacker - free stacking software

http://aurorawatch.lancs.ac.uk/   register for free e-mail warning of an Aurora

http://www.britastro.org/dark-skies/   The Campaign for Dark Skies site

http://www.heavens-above.com/   Heavens Above site for ISS and Iridium Flare predictions

NASA’S SPACE PLACE

Dark Clues to the Universe

By Dr. Marc Rayman

        Urban astronomers are always wishing for darker skies. But that complaint is due to light from Earth. What about the light coming from the night sky itself? When you think about it, why is the sky dark at all?

        Of course, space appears dark at night because that is when our side of Earth faces away from the Sun. But what about all those other suns? Our own Milky Way galaxy contains over 200 billion stars, and the entire universe probably contains over 100 billion galaxies. You might suppose that that many stars would light up the night like daytime!

        Until the 20th century, astronomers didn't think it was even possible to count all the stars in the universe. They thought the universe was infinite and unchanging.

        Besides being very hard to imagine, the trouble with an infinite universe is that no matter where you look in the night sky, you should see a star. Stars should overlap each other in the sky like tree trunks in the middle of a very thick forest. But, if this were the case, the sky would be blazing with light. This problem greatly troubled astronomers and became known as “Olbers’ Paradox” after the 19th century astronomer Heinrich Olbers who wrote about it, although he was not the first to raise this astronomical mystery.

   Ngc4414_hst.jpg  To try to explain the paradox, some 19th century scientists thought that dust clouds between the stars must be absorbing a lot of the starlight so it wouldn’t shine through to us. But later scientists realized that the dust itself would absorb so much energy from the starlight that eventually it would glow as hot and bright as the stars themselves.

     Astronomers now realize that the universe is not infinite. A finite universe—that is, a universe of limited size—even one with trillions of stars, just wouldn't have enough stars to light up all of space.

     Although the idea of a finite universe explains why Earth's sky is dark at night, other factors work to make it even darker.

     The universe is expanding. As a result, the light that leaves a distant galaxy today will have much farther to travel to our eyes than the light that left it a million years ago or even one year ago. That means the amount of light energy reaching us from distant stars dwindles all the time. And the farther away the star, the less bright it will look to us.

        Also, because space is expanding, the wavelengths of the light passing through it are expanding. Thus, the farther the light has travelled, the more red-shifted (and lower in energy) it becomes, perhaps red-shifting right out of the visible range. So, even darker skies prevail.

     The universe, both finite in size and finite in age, is full of wonderful sights. See some bright, beautiful images of faraway galaxies against the blackness of space at the Space Place image galleries. Visit: http://spaceplace.nasa.gov/search/?q=gallery

This Hubble Space Telescope image of Galaxy NGC 4414 was used to help calculate the expansion rate of the universe. The galaxy is about 60 million light-years away. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

        This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

CONTACTS

Chairman     John Vale-Taylor      pjvalet1@btinternet.com

Secretary & Events                 Phil Berry             01892 783544          philberryemail@gmail.com

Treasurer            Mike Wyles                          01892 542863               mike31@madasafish.com

Editor            Geoff Rathbone                         01959 524727                 geoff@rathbone007.fsnet.co.uk

Director of Observations       Brian Mills    01732 832691                  Brian@wkrcc.co.uk

Paul Treadaway                       01342 313799                                       paul_treadaway@btinternet.com

Wadhurst Astronomical Society website:           www.wadhurst.info/was/

SAGAS web-site            www.sagasonline.org.uk

Any material for inclusion in the November 2011 Newsletter should be with the Editor by October 28th 2011