WADHURST ASTRONOMICAL SOCIETY
NOVEMBER NEWSLETTER 2004
INDEX: MEETINGS, OTHER NEWS
Frey is a founder member of the Tenterden Astronomical Society and as part of
his Basic Astronomy talks gave us an intriguing talk on Parallax in Astronomy.
He presented his talk using PowerPoint on his laptop and displaying the
images through a digital projector with great effect.
through some of his old family photographs Martin found some taken when he was
12 years old and was struck by how many pictures of his knees existed and
realised that this was the result of parallax when his mother used the
viewfinder lens, which was separate from the camera lens.
compared this with a recent experience he had had whilst observing the
occultation of the planet Saturn by the moon in April 2002 from Appledore in
Kent. At the time of occultation a
friend of his in Newcastle rang to say he had already seen it.
Worse was to come when Martin missed the reappearance of Saturn!
The reason was because of parallax due to their relative positions and
the closeness of the moon to the earth. From
Newcastle the occultation took 38 minutes, but from Appledore the occultation
took place nearer the rim of the moon and took only 25 minutes.
briefly talked about the history of using the Transits of Venus to estimate the
distance of the Sun from the Earth. In
1639 the Reverend Jeremiah Horrocks was the first astronomer to use the timings
of the transit of Venus to calculate and estimate of the distance of the Sun
from the earth. He made the
distance 59,400,000 miles, 64% of the accepted distance today.
1761 and 1769 further observations of the transits of Venus enabled astronomers
such as Jean-Baptiste, Chappe d'Oloroche in France and David Rittenhause in
Pennsylvania to achieve much better results.
With more accurate methods of measurement then available, estimates of
between 91,000,000 miles and 97,500,000 miles were made.
(97 to 104% of the distance known today)
were also told an interesting story about measurements taken by Aristarchus of
Samos who lived in 320 to 250 BC. He
waited until the earth/moon/Sun formed a right angle, then by measuring the
angle between the moon and the Sun he produced a predicted distance 390 times
the distance of the earth to the moon. But
found this quite unacceptable and announced a much lower distance.
referred to an article in the September issue of Sky and Telescope this year,
called, "The lunar Parallax Demonstration Project" written by Peter
Lawrence, a friend of his. In it
Peter describes a project where he put together a number of photographs of the
moon taken at various sites around the world at a precise time during the lunar
eclipse of 9th November 2003 when the contrast between the background stars and
the luminosity of the moon was at its best.
He found the effects of parallax quite easy to see.
He also noted photographs taken in the USA and Europe showed slightly
different parts of the lunar surface, another effect caused by parallax.
also noted that at any one time from one point of observation on the earth's
surface, a maximum of 50% of the surface of the moon can be seen, but because
the orbit of the moon is elliptical, this enables us during a period of time to
see a total of 59% of the surface. This
effect is called libration.
was Copernicus who openly stated that the Sun was at the centre of the solar
system with the stars at a vast distance.
Bradley in the 18th century noted the displacement of stars in a year, and from
this confirmed the earth's orbit around the sun although the angular distance
was too fine to be measured at the time.
later used Bradley's star charts and with more accurate instruments improved
them to produce the most accurate star charts yet. In 1838 using parallax he observed 61 Cygni moving against
the background stars and estimated its distance to be 10.3 light years away.
(Now known to be 11.5 light years distance, showing just how careful he
must have been with his measurements)
fact Martin said that Thomas Henderson, Royal Astronomer at the Cape of Good
Hope, used parallax to measure the distance of Alpha Centauri as 4.3 light
years; five years earlier than Bessel had published his measurements, but
Henderson didn't announce his results for another two years later.
talk closed with Martin saying that some star positions are now so accurately
know that they can be "visualised" from a theoretical point beyond
them and looking back towards the solar system.
The position of stars will be even more accurately know during the GAIA mission which is due to take place in about 2010, and then the story will be continued...
next meeting is on Wednesday the 17th of November when the speaker will be our
own member Ian King whose talk is called "Wide Field Imaging".
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.
will also be the opportunity to discuss informally the future of the Society in
advance of the AGM in December. We
have now received a number of offers from members prepared to join the
Committee, which is great news, although it would be good to hear from one or
two more members.
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Wednesday December the 15th we hold the Society's Annual General Meeting and we
hope as many members as possible will be able to come along.
speaker at this meeting will be Norman Walker who was a professional astronomer
and has visited us before. The
title on this occasion will be "What you always wanted to know about
astronomy and were afraid to ask". He
is very good and it is worth thinking of those astronomy related questions whose
answers have eluded us in the past.
a planetary note
know that the clocks have now gone back and the mornings are that little bit
lighter for a while, but it is worth grabbing a pair of binoculars just before
dawn on a clear morning to observe Venus, Mars and Jupiter.
They are beginning to separate a bit now but still make a good group and
although the moon is about to reappear it will be a thin crescent for a while.
A NOTE FROM THE TREASURER
is suggested that one if not two of the rules included in our Constitution are
in need of amendment. Next month's
AGM would be a good time to take action. One
can only assume that in December 2001 no ordinary member was
burning/stimulated/inclined to take their turn on the Committee of the Society.
In order to keep it going in the face of such enthusiasm, the majority
chose to weaken the draft rules before their adoption.
It is therefore proposed that paragraph 5.5 should be MODIFIED, this time
to read, "The elected term shall be for ONE year".
In addition a draft rule deserves to be REVIVED as paragraph 5.8, this
time to read "No member shall hold the same office for more than THREE
years". A committee no longer
locked in to a job for life is more likely to take its brief opportunity to
promote new ideas.
might be the time to consider a reduction in the size of the Committee from the
nine listed in December 2001 to seven, namely: Chairman, Secretary, Treasurer,
Editor, Publicity & Web Site, Director of Observations, Member
without-portfolio. All these
matters can be discussed at the November meeting with a view to recommendations
being voted on and adopted at the AGM to be held on the 15th December 2004.
you know part of the 2003/4 Committee will be standing down in December.
The other part is willing to provide a measure of continuity.
It is encouraging to learn that at least three ordinary members have
indicated their willingness to join the new committee.
More are invited to come forward so that we can HOLD AN ELECTION on truly
(non political) democratic lines.
will be pleased to learn that we did conclude the last financial year with a
modest surplus of £80. If nothing
else the old team will be leaving a comfortable balance at the bank to their
successors for the future benefit of the Society. Just a gentle reminder - Subscriptions are now due for our
year, which began on 1 November 2004.
is worth remembering that from a standing start 7 years ago the Society has
become (by F.A.S. standards) one of the larger middle size societies.
number of copies of the Society's Constitution will be available at our November
Geoff Rathbone 01959 524727
Any material for inclusion in the December Newsletter should be with the
Editor by November 30th 2004
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