WADHURST ASTRONOMICAL SOCIETY
JULY NEWSLETTER 2004
INDEX: MEETINGS, OTHER NEWS, CONTACTS
changed the advertised subject of her talk about the Sun to the highly
appropriate Transit of Venus.
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.
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.
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.
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.
recently visited Paris and gave a very interesting talk about some of the
astronomical and related historical sites he had visited during his stay.
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.
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.
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.
enthusiastic talk was both informative and entertaining.
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.
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.
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.
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
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.
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.
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.
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.
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.
have found information on Registrax and the facility to down load the share-software
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
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.
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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.
meetings resume again on Wednesday the 15th of September 2004.
Murray R. Barber 01892 654618
Doug Biswell firstname.lastname@example.org
Sec: Joan Grace
& Web Site: Michael
for the September Newsletter should be with the Editor by August 31st
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