WADHURST ASTRONOMICAL SOCIETY

JULY  NEWSLETTER  2004

INDEX: MEETINGS, OTHER NEWS, CONTACTS

 

MEETINGS

LAST MEETING

Member's Evening

The June Meeting was an enjoyable evening open for members to give their own talks.  It was well attended and three members gave talks about their own experiences and interests and the meeting turned out to be both very informative and entertaining promoting plenty of discussion.

  The Transit of Venus

Given by Joan Grace

Joan changed the advertised subject of her talk about the Sun to the highly appropriate Transit of Venus.

In preparation for her Transit observations, Joan visited several web sites to obtain as much data as she could and found a lot of useful information at www.VT-2004.  For the actual observation she had considered using binoculars but found stability a problem, so she decided to use the Society's own refractor to project an image of the sun onto a suitable screen, first removing the finder scope for better access and also preventing the focused heat from the sun becoming a hazard.

Because the sun would be in line with the telescope and the projected image, a large cardboard screen was needed around the scope, to increase contrast so that the image could be photographed more easily.  Joan had to extend the focus position of the eyepiece to obtain a suitably sized and focused projected image.  Some time was spent adjusting a digital clock to give the correct time to the nearest second.

On the morning of the Transit, Steve Andaman joined Joan on a local knoll with his cassegrain telescope, which was ideal for projecting the sun's image because the eyepiece is at right angle to the direction of the sun's light and so provided a good contrast ratio.

They very carefully measured the time of the various contact points, despite the "tear-drop effect which made precise timing difficult to judge.  These results were then submitted to the www.VT-2004 web-site which returned the calculated results of the distance of the sun from earth, and also provided a graph of the results from the 2,070 observers who had taken part.  The graph had a very marked peak near 93, 000, 000 miles.  Joan's results were fairly close and were a credit to the real meaning of the amateur observer.

 

Some Astronomical Exhibitions and sites of interest in Paris

Given by Mike Wyles

Mike recently visited Paris and gave a very interesting talk about some of the astronomical and related historical sites he had visited during his stay.

He remembers some while ago discussing the work of Jean Bernard Foucault with Duncan Goulding, in particular Foucault's pendulum and Mike had become interested in finding out more about the physicist in his home city of Paris.  He did in fact find Foucault's grave in the cemetery in Montmartre where many other famous French citizens are buried such as composer Delibes and playwright Alexandre Dumas.

Mike eventually found the replica of Foucault's 220 feet high pendulum in the Panthéon, although the original is in the Museum of Science, a church.  It was explained that one oscillation of the pendulum took 16 seconds, turning 11o 17' per hour.

The one place Mike would have wished to visit was the Paris Observatory, but he discovered too late that it was necessary to book up at least two weeks in advance.  It was a pity because many of Foucault's telescopes were exhibited here, but Mike did discover one very important landmark in the grounds of the Observatory, and that was one of the markers of the original French meridian line.  This tiny tile had once been one of a line of many others both inside the grounds and outside, indicating the continuing line into the far distance.

Mike's enthusiastic talk was both informative and entertaining.

 

  Computer software and enhancement in astrophotography

  Talk given by Murray Barber

Murray began his talk by showing us a detailed picture of Saturn and its ring system and then spoke of the sort of telescope needed to resolve the kind of details we were able to see.  Quite a lot of latitudinal surface markings were visible but our attention was concentrated on details in the rings themselves.  He talked about the Dawes Limit that relates the aperture of a telescope to its ability to separate two very close stars, measured in seconds of arc.

The Moon would just fit inside the Cassini gap, the dark gap towards the outer edge of the rings.  At the distance of Saturn from earth, a telescope would need to be able to resolve something in the order of 0.65 seconds of arc, which from the Dawes Limit would suggest that the telescope would need to have an aperture of at least 10 inches. 

Then Murray looked at a tiny gap almost at the edge of the ring system called the Encke Division, the Holy Grail for amateurs.  But the Encke Division is only 325 km wide!  He posed the question of how it was possible for some amateurs, one using a 6-inch Maksutov telescope, to produce photographs showing not only the Cassini gap but also the Encke gap using fairly modest telescopes.

On a trip to observe the close approach of Mars during opposition from Las Palmas in the Canary Islands, Murray met Damian Peach and was astonished at the detail of his processed images of the surface markings on the planet using his 10-inch Mead telescope.

Murray considered how computer software was making this kind of detail possible.  He has done a lot of work recently using Valerie's computer (when she wasn't looking...) and looked into how any available contrast in the recorded image could be enhanced, including the Encke Division in favourable conditions and showed various examples, but also warned of the danger of getting to the stage where noise could be resolved as detail.

We then saw slides of Jupiter and Murray mentioned the difficulty of using the computer when details had lower contrast ranges.  We even saw the phasing of Jupiter when at quadrature.

Murray showed us some of his own remarkable processed images of Mars, first only the ice caps could be seen, and then after processing 600 superimposed frames recorded on his CCD StellarCam video camera he began to achieve details as small as 0.7 seconds of arc.  After using electronic sharpening we were even able to see details down to 193 km across.  A comparison was made with images from the Hubble Space telescope and Murray's results were very encouraging.

Finally we were shown images of the Swan Nebula using between 20 and 30 images processed by Registrax software.  The slide showed excellent and impressive detail.

Murray concluded by saying that in the short time he has been processing images through computer software, he had learnt a tremendous amount and continues to do so, but also said that software and hardware are also improving all the time so it is a rapidly developing astronomical tool.

 

I have found information on Registrax and the facility to down load the share-software at: http://aberrator.astronomy.net/registax/

NEXT MEETING

The next meeting of the Wadhurst Astronomical Society is on Wednesday 21st July 2004 when Murray Barber will be bringing the Starlab planetarium and demonstrating new innovations in mobile planetarium technology specifically, the new FibreArc light source and Multilens cylinder.  The star effect is very different to the normal Starlab projector and Murray hopes to demonstrate a direct comparison, which he says is very marked.

As usual, the meeting will be held in the Drama Studio at Uplands College.  The doors open at 7.15 and the meeting starts at 7.30 prompt.

    Sadly, this will be the last time that Murray will be able to Chair the meetings due his increasing commitments outside the Society, as mentioned in the last Newsletter.  It is important that we find a member prepared to take on the task.  They would not be expected to take on the roll for as long Murray has been doing it by any means, but we do need someone ready to take over for the September meeting.  Murray has said that he is very willing to talk about the position to anyone interested in finding out more.

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OTHER NEWS

AUGUST

There is no meeting of the Society in August when we hope we can enjoy long summer evenings just sitting in the garden drinking our favourite beverage and thinking about what the winter skies will be like.

The meetings resume again on Wednesday the 15th of September 2004.

 

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CONTACTS

Chairman:      Murray R. Barber               01892 654618

murray.barber@virgin.net

Secretaries:  Steve Camp       steve.camp52@btopenworld.com

                  Doug Biswell           dougrbiswell@aol.com

Treasurer:      Ian Reeves                        01892 784255

Membership Sec:   Joan Grace             01892 783721

Editor:           Geoff Rathbone                01959 524727

Geoff@rathbone007.fsnet.co.uk

Publicity & Web Site:      Michael Harte       01892 783292

michael@greenman.demon.co.uk

Dir. of  Obs:  Sean Tampsett                01892 667092

sean_tampsett@hotmail.com

 

Copy for the September Newsletter should be with the Editor by August 31st  2004

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