WADHURST ASTRONOMICAL SOCIETY
JULY NEWSLETTER 2008
INDEX: MEETINGS, OTHER NEWS, CONTACTS
Members of the Committee are respectfully reminded that there is a meeting of the Committee on Tuesday 1st of July at 1930 in the Abergavenny Arms, Frant.
As always, any member of the Society is very welcome to come along and join us. The meeting usually lasts about an hour.
Since this was one of the longest days of the year, the Society held a Telescope Open Evening.
A number of telescopes and other instruments had been brought my member's; amongst them was the Ian Reeves 4-inch refractor telescope. This is a good medium-sized telescope with an equatorial mount without motor drives. This telescope is available to members to borrow and with its sturdy metal tripod, is an excellent instrument for any degree of observing skills.
Also present was a Coronado PST (Personal Solar Telescope) that has a Hydrogen-alpha filter making it possible to observe the irregular surface of the Sun such as the turbulent area around Sunspots and Prominences at the edge of the visible disk.
There were two pairs of stabilised binoculars; very useful tools for wider field observing. Phil Berry also brought a surface-silvered mirror that enabled the observer to look downwards rather put a crick in their neck.
A very interesting telescope was a computer driven Maksutov Nexstar 5 that had a CCD camera attached in place of the eyepiece. This camera took 60 frames a second and then aggregated them, effectively increasing the light gathering power. The output from this clever little gadget was then displayed on a small flat LCD screen mounted on top of the telescope.
In one corner was also a Celestron 11-inch Cassegrain telescope with a German equatorial mount. It was displayed using an offset Mylar filter reducing the light gathering by 50,000 making it possible to observe the Sun in visible light.
Phil Berry introduced the evening by giving the final details for the Society's visit to the Old Observatory at Greenwich the following Saturday.
Phil also referred to the ongoing discussion about the proposal to install flood lighting at a Wadhurst Tennis Club court. At present most of the plans had been passed apart from that of the Local Parish Council who had already rejected them. There is another meeting of the Parish Council about to take place.
The Society has submitted objections to the council and it is intended to keep members up to date with any progress, one way or another, that is made.
"Our Sky Through Telescope and Binocular"
By Alex Filippenko (DVD)
From a large collection of DVDs forming an astronomical course, Phil invited us to watch one called "Our Sky Through Telescope and Binocular"
This thirty-minute lecture took us through the pinhole "lens" to refraction using glass shaped to bring parallel beams of light to a "focus" at a distance from the lens called the focal length.
Alex Filippenko also demonstrated the inverted image at the focal plane and how another lens; an eyepiece could focus the image suitable for viewing by the human eye. Then how the focal length of the object lens divided by the focal length of the eyepiece gave the magnification obtainable.
Dutch opticians made the first telescope but it was Galileo who improved the arrangement and lenses so that he could try and interest the navy since he could now demonstrate that ships could be observed well before the unaided human eye could see them.
Colour aberration was shown when light of different frequencies (colours) came to focus at different planes, causing coloured edges to objects particularly near the outer limits of the lens.
Modern methods have reduced this effect with refracting telescopes but Isaac Newton was the first person to use a curved mirror which removed chromatic aberration, although it was found that the best arrangement was to use a diagonal plain mirror in the light path to reflect light from the main mirror to the eye-piece.
Alex Filippenko moved on to the Cassegrain telescope where the light from the main parabolic mirror is reflected back to a centrally placed hyperbolic mirror that passed light back through a hole in the centre of the main mirror. This had the advantage of reducing the size of the telescope yet maintaining a long focal length.
Finally we were introduced to the Schmidt-Cassegrain where light passes through a large thin lens at the front of the telescope before reaching the main mirror, with the secondary mirror usually being attached to the centre of this lens.
We then looked at examples of some of the objects astronomical telescopes and binoculars help us to see such as the moon and its craters and lava plains or Maria.
Moving away from the earth we viewed images of the planets and their moons, then to the Sun.
Looking further we were shown globular cluster and the Ring Nebula in Lyra where in the past a red giant, about 2,000 light years away exploded and we now see the gaseous material expanding from a white dwarf in the middle at the rate of about 1 arc second per century which is about 20 to 30 km per second, suggesting that the red giant exploded 20,000 years ago.
We star-hopped from the "W" in Cassiopeia to The huge Andromeda galaxy, and still further to far distant galaxies.
These DVDs each cover a different aspect of astronomy quite clearly and we have seen one or two at past meetings of the Society. They appear to be pretty popular amongst members and it maybe of interest to show more in the future.
Wednesday 16th 2008. There will be a talk given by James Fradgley called "Orbital Oddities - Strange Goings-on with 3 or more bodies" covering Lagrange Points, Resonances, Roche Limits, and lots of odds and ends with simulations.
James is a member of the Bournemouth Natural Science Society in Dorset.
The meeting begins at 1930 although members are invited to arrive anytime after 1900. This is a good time to exchange ideas and discuss problems.
The venue as always is in the Upper Room of the Methodist Church at the east end of Wadhurst Lower High Street, opposite Uplands College. (For those with SatNav - the Post code is TN5 6AX)
FUTURE MEETINGS & EVENTS
Wednesday 23rd July 2008 The "Hands-on" group are meeting at Phil Berry's house to see the progress he has made with his observatory. He has achieved a lot since he talked to the group's last meeting in March.
Any full member of the Society is welcome to come and Phil suggests we meet at his house from 1900. He will bring maps of how to get there to the 16th of July meeting.
Saturday 23rd August 2008 There is no Society meeting in August but Michael Harte and his wife Claire have very kindly invited the Society to an Astro-Barbecue. This weekend is the late August Bank Holiday weekend and all members are welcome.
In the past is has been a very enjoyable event and we usually take the occasional telescope and binoculars. There is often the appearance of the latest gadget and members take great delight in trying them out.
Barbecue facilities are provided and we need to take just our own food and drink.
Michael suggests that members aim to arrive around 7.00 pm.
Further details will follow nearer the time.
Wednesday 17th September 2008 At this meeting there will be a talk by John Punnett, a member of the Orpington Astronomical Society. He calls his talk "An Enthusiastic Amateur's Journey in Astrophotography".
It is worth looking at John's website at: http://homepage.ntlworld.com/john.punnett/
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VISIT TO GREENWICH OBSERVATORY
At the far end of Blackheath Avenue in Greenwich Park is Wolfe's statue and to the left, the Old Greenwich Observatory.
It was beautifully clear day with the Maritime Museum at the bottom of the park and beyond that the river, overlooked by the ever-growing Docklands money factory, with the backdrop of north-east London sprawling to the distant horizon.
This was warm and sunny day when sixteen members of the Society met Gilbert Satterthwaite by the famous 24-hour clock positioned on the outer wall of the observatory.
Gilbert's ambition to be an astronomer had been fuelled when as a schoolboy he and his father had looked eagerly through the railings at the buildings.
He realised his ambition after achieving the necessary standard in mathematics as well as physics and passed an interview to become an assistant positional astronomer at Greenwich observatory in 1952.
As a group, we entered the museum and were shown the sites of the first quadrant used by Flamsteed although its whereabouts are now not known.
From here Gilbert showed us where a small shed had once existed on a north-facing terrace, housing a telescope that was used as the first transit telescope, but there was nothing left here now to show its presence.
We visited the Octagon Room, the first observatory at Greenwich, built by Christopher Wren but found to be unsuitable because it had a limited number of very tall windows to use a telescope through and it also had a roof, all of which restricted the observable sky.
We passed through the newly refurbished Time Gallery and on to see Halley's Quadrant, then we looked at Bradley's transit circle. This instrument had been moved from Bradley's Prime Meridian when Pond improved conditions at the observatory and installed a larger instrument on Bradley's meridian.
Gilbert said that this meridian is the one the Ordnance Survey maps are based on. Airy's huge Transit Circle marked the current Prime Meridian, 19 feet to the east of Bradley's meridian. The difference in time between the two is just 51 milliseconds!
George Airy had designed and supervised the building of the final transit instrument, which used an 8 1/4-inch refractor with a focal length of 12-feet.
The instrument was counterbalanced to reduce wear and minimise errors. The instrument errors were carefully reduced using very many techniques devised by Airy. As an example, the blocks used to support the instrument were a combination of granite and Portland stone. Even the coefficient of expansion between the two materials was taken into account and compensated for.
Gilbert took readings with this instrument between 1952 and 1954 when Greenwich ceased to be used and measurements were moved to Herstmonceux in East Sussex.
In fact it was Gilbert who had the distinction of taking the last readings using this instrument.
We all watched whilst Gilbert climbed down into the pit beneath the huge transit telescope and demonstrated the various movements and described the way readings were taken and then how the errors were painstakingly reduced.
During the visit, Gilbert never stopped relating stories and providing information about the observatory and was able to recall names, dates and figures over and over again providing a very detailed tour.
Our group finally visited the Peter Harrison Planetarium to see a programme called "The Sky Tonight Live" where we were taken through the night sky, as it would be this night using the new computerised projector.
The projector is far better than the one that had been used at the late London Planetarium in Baker Street, but still not as sharp as the old Zeiss projector that used to be housed in the old Greenwich planetarium, but it was able to show graphics and data enabling our astronomer guide to illustrate in more detail some of the objects to be seen.
Finally we were taken slowly out of our orbit around the Sun, out of the solar system, and out of the Milky Way until we could look back and see ourselves amongst our local cluster of galaxies.
The tour was wonderfully organised and grateful thanks go to Phil Berry and of course, to Gilbert Satterthwaite, our brilliant guide.
ENTRY FEE TO THE PLANETARIUM
Phil Berry arranged a group ticket via the Internet, which reduced the entrance fee from £6 to just £3.28 per member. Those who have not paid him yet, like me, can catch up with him at the next meeting on Wednesday July 16th.
THE "HELP LIST"
The "Help List" on a clipboard is available at each meeting and is for members to use when asking for help or information. This is a useful way of introducing problems being experienced and queries by members.
SKY NOTES FOR JULY
Mercury is not suitably placed for observation in July, rising only just before the Sun.
Venus is also badly placed for observation this month.
Mars at magnitude +1.7 lies in the constellation of Leo (the lion). By the middle of the month it will set before 23.00 BST but will be lost to twilight well before that. It passes close to Regulus (a Leonis) on July 1st.
Jupiter at magnitude -2.7 is rather low in the sky reaching a maximum height of only 16° above the horizon in Sagittarius (the archer). At the beginning of the month it rises at around 22.00 BST. Despite its low altitude it presents a reasonably sized disk and of course the four brightest moons are easily seen in a small telescope or binoculars.
Saturn is still in Leo and will be less than one degree from Mars on the 11th. It's brightness, now at +0.8 continues to drop which will make it more difficult to locate as it too is swallowed up by twilight. By the end of the month it will set before 22.00 BST.
As usual I've only included events for stars down to around magnitude 7.5 that occur before midnight BST. DD = disappearance at the dark limb whilst RD = reappearance at the dark limb. Times are all BST.
Phases of the Moon for July
|New||First Quarter||Full||Last Quarter|
The Perseid meteor shower begins on July 23rd although rates will remain low until we get closer to the August maximum.
Below are details of the most favourable passes of the ISS this month as seen from Wadhurst. The information given is for when it is at maximum altitude, so it is best to look a few minutes before this time. There are many more passes visible but some suffer from low altitude whilst others occur after midnight. Full details of visibility can be found at: www.heavens-above.comTimes are all BST.
August 1st - Partial eclipse of the Sun beginning at 09.33 BST.
August 12th - Maximum of the Perseid meteor shower.
August 16th - Partial Lunar eclipse beginning at 20.35 BST.
NASA SPACE PLACE
By Dr. Tony Phillips
Congratulations! You're an oceanographer and you've just received a big grant to investigate the Pacific Ocean. Your task: Map the mighty Pacific's wind and waves, monitor its deep currents, and keep track of continent-sized temperature oscillations that shape weather around the world. Funds are available and you may start immediately.
Oh, there's just one problem: You've got to do this work using no more than one ocean buoy.
"That would be impossible," says Dr. Guan Le of the Goddard Space Flight Centre. "The Pacific's too big to understand by studying just one location."
Yet, for Le and her space scientist colleagues, this was exactly what they have been expected to accomplish in their own studies of Earth's magnetosphere. The magnetosphere is an "ocean" of magnetism and plasma surrounding our planet. Its shores are defined by the outer bounds of Earth's magnetic field and it contains a bewildering mix of matter-energy waves, electrical currents and plasma oscillations spread across a volume billions of times greater than the Pacific Ocean itself.
"For many years we've struggled to understand the magnetosphere using mostly single spacecraft," says Le. "To really make progress, we need many spacecraft spread through the magnetosphere, working together to understand the whole."
Enter Space Technology 5.
In March 2006 NASA launched a trio of experimental satellites to see what three "buoys" could accomplish. Because they weighed only 55 lbs. apiece and measured not much larger than a birthday cake, the three ST5 "micro-satellites" fit onboard a single Pegasus rocket. Above Earth's atmosphere, the three were flung like Frisbees from the rocket's body into the magnetosphere by a revolutionary micro-satellite launcher.
Space Technology 5 is a mission of NASA's New Millennium Program, which tests innovative technologies for use on future space missions. The 90-day flight of ST5 validated several devices crucial to space buoys: miniature magnetometers, high-efficiency solar arrays, and some strange-looking but effective micro-antennas designed from principles of Darwinian evolution. Also, ST5 showed that three satellites could manoeuvre together as a "constellation," spreading out to measure complex fields and currents.
"ST5 was able to measure the motion and thickness of current sheets in the magnetosphere," says Le, the mission's project scientist at Goddard. "This could not have been done with a single spacecraft, no matter how capable."
The ST5 mission is finished but the technology it tested will key future studies of the magnetosphere. Thanks to ST5, hopes Le, lonely buoys will soon be a thing of the past.
Learn more about ST5's miniaturized technologies at : nmp.nasa.gov/st5
Kids (and grownups) can get a better understanding of the artificial evolutionary process used to design ST5's antennas at: spaceplace.nasa.gov/en/kids/st5/emoticon
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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Chairman John Vale-Taylor
Phil Berry 01892 783544
Treasurer Mike Wyles 01892 542863
Publicity & Website Michael Harte 01892 783292
Newsletter Editor Geoff Rathbone 01959 524727
Any material for inclusion in the August 2008 Newsletter should be with the Editor by July 28th 2008
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