Castle Point Astronomy Club
Castle Point Astronomy Club Diary 2006
by Andrew Mowbray
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Wednesday 4th January 2006

First meeting of the Year

An informal coffee evening was scheduled, but our observant Observing Director noticed that the skies were clear so e-mailed the group to declare an observing evening. This ensured that at 7:30pm, half before the start, the powers that be pulled the cloud across the sky like a roller blind being drawn across a window.

We adjourned in side where Mike asked what the Club Members had been up to on the astronomical front during the Christmas Break. I reported helping a friend in Epping set up a 4.5" reflector he had bought of someone who had not used it much because he didn't like going out in the garden at night due to all the wildlife rustling in the undergrowth. We set it up in his sloping garden and got very good views of Mars, Saturn, Mizar, M42 (Orion Nebula), M45 (Pleiades) and Saturn.

Dee had acquired an equatorial wedge for her big Meade scope. This had proved to be very heavy and was wearing grooves in her kitchen floor when she dragged it out in the garden. She wanted it so her scope would track equatorially when taking photographs, thus avoiding the object twisting, as occurs when using an alt- azimuth mount.

Dave Smith said he had started an OU Astronomy Course and was finding it interesting but challenging. This started a discussion on OU courses. Mike said he had done some in the past, including quantum mechanics. This had been very challenging. I mentioned the Heisenberg uncertainty principle. Mike decided to try and explain how this makes the Sun work. The Sun consists largely of hydrogen atoms under such tremendous pressure and temperature that their one electron is stripped off, leaving then as a soup of positively charged protons. These need to come together to cause nuclear fusion and produce a helium atom plus heat for the Sun to work. However all protons hold the same charge and like charges repel. He asked Andy and Gerald to come up and play the role of two protons repelling each other, which they did very well.

He said the position of a proton depends on where it is when you measure it. Protons can therefore, under the uncertainty principle, suddenly appear somewhere else, it this might be right next to another one, allowing fusion. Andy and Gerald leapt towards each other and embraced to demonstrate this.

After this, Mike briefly went through the arrangements for the Open Night and we all adjourned for refreshments and to see if Schrödinger's Cat was hiding in the fridge.

Saturday 7th January 2006

Public Open Night

The Club's first Winter Open Night at Hadleigh Country Park took place this evening. It is held in conjunction with the Southend Planetarium and the County Park Ranger Service. Saturday morning was grim and grey, but during the afternoon it brighten up and the sky cleared. It was meant to start at 5:30pm, but the local paper had put 5:00pm so we had to get there by 4:30pm. Terry was on gate duty and directed us to the car park where we were to set up our telescopes as the field we normally use was too boggy to use. I had borrowed Ted's 6" reflector to use as an access scope for visitors in wheelchairs. I had never used it before so it was steep learning curve, but we did manage to provide some nice views for a wheelchair visitor. There were a good array of scopes of all shapes and sizes and Terry had made red light illuminated signs to indicate what each scope was showing. At 6:00pm, the clouds rolled in and brought an end to the evening, but we had about 120 people visit so it was a success.

Wednesday 11th January 2006

Beginners/Observing Evening

This was an observing night and for once it was actually clear. We had an almost full Moon to content with, so deep sky objects were a challenge. Saturn, Mars, M42, M43, Mizar and the Pleiades seem to be the main objects of interest.

Wednesday 11th January 2006

Mike Culley and Jim Vincent - Registax

Mike gave a brief report on the Open Night and showed a few pictures taken by Andy.

Jim and Mike then gave a talk on the Registax programme. This allows you to take an AVI movie of a planet, taken with a web cam, which will probably wobble about and have some bits that are clearer than others and convert it to a good picture. It does it by taken all the frames of the movie and stacking them to get the best from each one.

Mike demonstrated how this works using some software he had written. All computer pictures are stored as numbers and you can use a mathematical technique called iteration to remove the noise from the pictures, which he demonstrated by cleaning up an image of Mars he had taken.

Jim then showed the various bits of equipment he uses to attach the web cam to a telescope. He uses an illuminated reticule to line the telescope up and then puts on the web cam. A par focal ring can be sued to keep the two at the same focus. Web cam chips have a very small area on which the light can fall so getting it lined up can be tricky

Wednesday 25th January 2006

Beginners/Observing Evening

This was an observing night and once again it was actually clear. This time we had no Moon so much more could be seen. We did have some cloud patches, but the evening was a success. Some got there early to observe an occultation of By Cancri* (SAO 98054) by Saturn which started at 1837.

Wednesday 1st February 2006

Nick James - Astrophotography with a DSLR Camera

Tonight we had a guest speaker. Nick James gave us a talk on Astrophotography with a DSLR (Digital Single Lens Reflex) Camera. He first told us how he had previously used large slide film, but this was now becoming difficult to get hold of as it production of it had stopped.

He is involved in the search for Novas. This involves taking pictures of the same areas of the sky on different nights and seeing what has changed. He was not convinced by digital cameras, but saw what they could do and became convinced.

He explained that in a web cam, there was a very small CCD or CMOS chip which acts as the light gathering device. DSLR cameras have a much larger one so they can take a much larger image with higher resolution and better light gathering.

He explained how the picture should be taken in the native RAW format. Most digital cameras process them into JPEGs, which causes a loss of information.

He showed us various pictures he had taken of both terrestrial and astronomical objects and the details were superb.

As he takes a lot of them for scientific reasons, he is wary of processing them too much.

Another advantage of a DSLR is that standard camera lenses can be fitted to it, as can a telescope.

Saturday 4th February 2006

Public Open Night

The Club's second Winter Open Night at Hadleigh Country Park took place this evening. It is held in conjunction with the Southend Planetarium and the County Park Ranger Service. Saturday morning was once again grim and grey and the afternoon was not looking promising. However the trusty cloud forecast on the BBC was predicting a break in it later on so we all went down to the park to set up at 5:00pm for a 6:00pm start

Terry was on gate duty and directed us to the car park where we were to set up our telescopes, as the field we normally use was once again too boggy to use. I was with Ted using his 6" reflector to use as an access scope for visitors in wheelchairs and this was put to good use both for wheelchairs and as an overflow when Jim's 20" Dobsonian got busy

There was some lowing lying mist, but of most of the sky were OK. We had a brief period when it clouded up, but we were able to keep going to about 8:15pm. By 8:30 it had clouded over. Apparently we had the only hole in the cloud in the whole area. A family who were coming from Hockley were put off by cloud, even though it was clear at the same time at Hadleigh.

There were a good array of scopes of all shapes and sizes and we also had the camera and projector showing the Moon and Saturn on the big screen.

In all we had about 120 visitors again.

Wednesday 8th February 2006

Beginners/Observing Evening

For an unprecedented third time in a row we had an observing night that was clear. We had to contend with a nearly full Moon, but it was well attended and I managed to find several new objects I had not seen before.

Wednesday 15th February 2006

Dee Amos - Venus

This was to have been a talk on Matt's telescope by Matt and Tim, but Tim could not make it. Mike opened the evening with some amusing astronomical anecdotes. The first was about how during the first Moon landing they were able to ignore aborting after some warning had gone off as a last minutes drill had shown they could be ignored. He also showed a cartoon implying that President bush had agreed to go to Mars because he though there was oil there. Dee then stepped into the breach and gave us a very interesting talk on Venus. She showed us some of her images of it, went through the history of its observation including some tales of observations of transits of Venus across the Sun.

Wednesday 22nd February 2006

Beginners/Observing Evening

This was meant to be an observing night, but our run of luck with the weather had expired. Mike gave us another tale of how during one of the Moon Landing, the astronauts had to bang a switch which had a bit of metal caught in it to avoid aborting the landing.

Dave then continued the A to Z of Astronomy that he started last year. He gave a reap of A to M and then did N to Z. This included O for the Owl Nebula, Q for a Quasar, one of which ad been photographed by Pete. We had all the other letters including V for Virtual Moon Atlas (a new one has just been published on the internet) and Z for Zenith, which was currently cloudy, so he showed a picture of some clouds.

Wednesday 1st March 2006

Nik Szymanek - Observing from Hawaii

Tonight we had an excellent talk from Nik Szymanek, an outside speaker who told us about his experiences observing from Hawaii. He was sponsored by a grant from PPARC to go to the UK's telescopes on Hawaii and take pictures of them for publicity purposes.

He showed us some excellent pictures of the telescopes on Mauna Kea, on Hawaii's main island. These are located at 14,000 feet above sea level so are above most of the atmosphere and cloud, thus giving very good observing conditions.

The American's Japanese, Canadians and British all have telescopes on the mountain looking at visible, infra red and sub millimetre wavelengths. Many of the scopes here are inferometers which means they are several scopes acting together to form one much bigger virtual scope.

He showed us star trails, long exposure shots, views of the mountain and observatories and ended with a short video of the trip.

Saturday 4th March

Public Open Night

The Club's third Winter Open Night at Hadleigh Country Park took place this evening. It is held in conjunction with the Southend Planetarium and the County Park Ranger Service. Saturday was bright and clear and we had superb conditions for the evening. We all arrived at 5:30 to set up for a 6:30 start and we were on the main field this time as it was dry enough.

We had one hundred cars arrive within the first half hour and at one point it was so busy, the rangers had to turn cars away as the car park was full. In all we had over 500 visitors.

There were a good array of scopes of all shapes and sizes and we also had the camera and projector showing the Moon and Saturn on the big screen. A special treat was a pass of the International Space Station at 19:36 GMT. Mike blew a whistle a minute before, we all looked up and saw a bright light rising in the west as predicted. Shortly afterwards, another bright light appeared which was actually the ISS. There has been dome debate as to what the first one was. It was either the Progress 19 supply craft that had been jettisoned from the station or it was an orbiting rocket casing.

Wednesday 8th March 2006

Beginners/Observing Evening

This evening was cloudy. We had a recap of the Open Evening, We then had a brief mention of the outreach visit by Terry, Ted and myself to the University of the Third Age's Astronomy Club at Maldon where I gave a talk on the Cassini-Huygens mission and Terry crawled around on the floor between people's legs!

There was a brief discussion of the comet that can be seen at the moment in the morning sky at the moment. Pete was going to show some pictures of his telescope, but his CD-ROM would not work.

I then gave a talk on how to give talks, in order to encourage more people to present to the Club, especially on beginners' evenings that are indoors. He went through he main principles of giving a talk including how to structure it, how to use PowerPoint, keeping peoples' attention and how to handle questions.

Wednesday 15th March 2006

Question Time

This evening was based on the format of Question Time on the TV. We had a panel of "experts" consisting of Gerald, Jim, Andy, Brian and Ron with myself in the chair to keep order, not always successfully!

Questions asked including the best way of web camming with a cheap reflector, the DaVinci Code, black holes, quantum physics, the big bang and extraterrestrial life. All in all a very entertaining evening.

Wednesday 22nd March 2006

Beginners/Observing Evening

This evening was cloudy. Dave gave us a brief explanation of how eclipses occur in preparation for the total eclipse due the following week. He explained that eclipses occur at New Moon when the Moon is on the same side of the Earth as the Sun. B a cosmic coincidence the Moon is 400 times smaller than the Sun, but is also 400 times nearer so it appears to be the same size in the sky. thus when the Moon moves in front of the Sun it completely covers it giving an eclipse.

If the orbits of the Moon around the Earth and the Earth around the sun where aligned we would get a total eclipse every New Moon. The Moon's orbit  is actually inclined to the Earth's so they only occur occasionally. A large area of the Earth will see the Moon partly covering the Sun during an eclipse. this is known as a partial eclipse. Sometimes a very small track will have a partial phase followed by a total phase, when for a brief period, the Moon completely covers the Sun, causing the sky to go dark and making the Sun's atmosphere or corona appear. An annular eclipse occurs when the Moon is slightly further away and so sits inside the Sun's disk. A hybrid eclipse is a combination of a total and an annular.

At the start and end of a total eclipse, the Sun shines through the valleys of the Moon causing the diamond ring or Bailey's beads effects.

Finally a warning. Never look at the Sun through any instrument such as a camera, telescope or binoculars. This will cause instant and permanent blindness. This can only be done using specialist equipment by astronomers who know what they are doing. Never look at the Sun with your eyes as this will hurt them and can cause damage. Eclipses can only be viewed safely during the total phase when the Moon covers the Sun. During partial eclipses, projection of the image or approved eclipse glasses or filters should be used. (Not smoke glass, exposed film, CDs etc, all these are dangerous to use.) Welding glass can be used, but must be at least No 14.

Wednesday 29th March 2006

Total Eclipse

This was an informal meeting for those not away observing the Eclipse.

Wednesday 5th April 2006

Winter Picture Review

This was a chance for members to bring along the pictures they had taken during the Winter. There were contributions from Eddy, Jim, Pete and myself.

Wednesday 12th April 2006

Beginners/Observing Evening

This evening was cloudy. Mike gave a talk on galaxies. He went through the history of their observation and recognition, how they were classified by shape, how they behave and some good ones to observe.

Wednesday 19th April 2006

Eclipse Tales

Many members observed the eclipse of the 29th April, both the partial eclipse as see from England and the total eclipse seen from Libya and the south west coast of Turkey. I MCed the event and gave a brief introduction to eclipses in general and this one in particular.

Gerald, Ed and Dave then went through some photos of the public observation of the partial eclipse that they held outside Southend Civic Offices. Despite cloud, they did see it. Bruce showed some pictures he had taken through welding glass from Suffolk and Alan showed one he had taken through a solar filter on his ETX-90 from Hadleigh.

Mike then described his hair raising trip by coach across the Libyan desert to see four minutes of totality. he showed lots of pictures and we also had a slide show from some people who accompanied him.

Steve then described how and Lesley viewed the eclipse from a boat of the coast of Turkey and showed some pictures of totality along with their boat. He also described how they had to move around to find some clear sky.

Pete showed the pictures he took form his hotel near Side on the Turkish coast and also an animation of the whole eclipse he had compiled from pictures taken by someone else as the same place.

Ted was not there, but had given me some pictures he had taken from near Side where he watched it with the twins.

I  then described the two day trip he had taken to Kizilot near Side with Bernie, Eddie, Kevin, Jim and Simon. He described the quite hectic trip which involved lots of queuing due to the number of people of were all staying at the same place. They had a good view of totality and were interviewed by Chris Lintott of  "The Sky at Night" who also looked through Jim's telescope at the filtered partial phase. They took some good photographs, but all agreed that no photo did it justice. After the eclipse, some rare lenticular clouds were observed.

Many of the visitors to Turkey were overcome by the panic\awe that sets in at the start of totality.

I then gave a quick run through of when the next ones would be.

Wednesday 26th April 2006

Beginners/Observing Evening

This evening was cloudy. Terry displayed his PowerPoint skills and showed us some pictures and montages of past eclipses.

We then had notices. I said the Solar Eclipse on 29h March had not been a total eclipse of the Sun. It had been an occultation of the Sun by the Moon and it was the Earth that had been eclipsed.

Pete and Eddie mentioned they had been observing and imaging comet 73P Schwassmann-Wachmann, the comet whose many fragments were currently passing close to Earth.

Terry then gave us a choice of films to watch. We settled on a "Sky at Night Episode" about the Sun. This discussed the Sun,  including it structure and activity. This included the eleven year cycle of the Sun's activity, sun spots and the solar wind. Observations from the SoHo probe which is in orbit around the Sun at a LaGrange point was giving us new insight all the time.

The program then discussed the different types of stars that there are and there life cycles. These rang from very long lived, but small, dim  and quite cool brown dwarves, through red dwarves, yellow stars like the sun, right up to red giants and white super giants which are short lived, but very hot, bright and large.

I then mentioned a new theory that global warming may not be entirely due to human activities, but also caused by the Tunguska meteor explosion of 1908 which destroyed a lot of upper atmosphere ice crystals. A Russian scientist says the Earth was cooling until that point and started to warm up afterwards.

Wednesday 3rd May 2006

Jupiter

The meeting started with some trivia from me about the fact that the following day would have an interesting time sequence. At 1:02am and 3 seconds on 4/5/06, it would be 010203040506. This happens every 100 years. A leading mathematician on the radio said it was of no significance whatsoever. I also mentioned I had finally seen comet 73P Schwassmann-Wachmann which looked best through binoculars. The largest fragment, 73P C, was now naked eye visible.

We then moved on to the main topic of the evening which was a talk on Jupiter by Dee. Firstly she described the legend behind Jupiter. He was the Roman king and father of the gods. The Greeks called him Zeus, the Old English Jove. Things belonging to Jupiter, such as moons, of which it has at least 63, as called Jovian. The ancients knew of Jupiter in the sky, but they did not know that the planet, which is fifth out from the Sun, is the largest, but the name is appropriate

Galileo did not discover the four moons Io, Europa, Ganymede and Callisto, which are visible in binoculars and collectively named after him, but he was the first to really describe them and suggest that they went round Jupiter. until then, it was widely believed that everything went round the Earth.

Jupiter is a gas giant consisting largely of hydrogen and helium, similar to the Sun, although it could never become a star itself. Beneath the atmosphere is a liquid outer core and a metallic hydrogen solid inner core.

It has a huge magnetic field which extends as far as Saturn and generate more heat than it receives from the Sun.

Its magnetic and gravitational fields cause huge tidal effects on its moons. On Io for example, it causes active sulphur volcanoes which send out material which form a ring around Jupiter. On Europa, there is believed to be an ocean of liquid water below an icy crust. This may harbour life.

Jupiter also has little asteroids called Trojans which lead and follow it in its orbit around the Sun. They are located at LaGrange points.

She described the Pioneer, Voyager and more recently Galileo probes, which are been to Jupiter and sent make a huge amount of information. The first two were flybys, but the last went into orbit. It sent a probe into the atmosphere and was eventually crashed into Jupiter to avoid it contaminating Europa if it hit it.

After a break, Dee showed some photographs she had taken of Jupiter. Mike then told a tale of how the Galileo probe's main high gain antenna which had been designed to withstand the rigours of space flight, had not opened properly because it had been damaged whilst being transported on the pot hole ridden US freeway system. Fortunately signals can be received from the low gain antenna, but it is very, very slow.

All in all, a very interesting evening.

Wednesday 10th May 2006

Beginners/Observing Evening

For once it was clear, if a little misty. Before it got dark, the Solar Scope was set up to observe a very quite Sun with very few sun spots before it set. Once it got dark we had quite a few scopes and binoculars set up. We observed Jupiter, Mars and the comet 73P Schwassmann-Wachmann 3 amongst other objects.

Wednesday 17th May 2006

Debate

I was away for this one, but a debate took place about using automated scopes to observe from indoors versus manual observation outside. (I think!)

Wednesday 24th May 2006

Beginners/Observing Evening

A combination of daylight and torrential rain meant that any observing was out of the question tonight.

Firstly we had Terry go through some new gadgets that Maplin had brought out. There was a combination telescope and CMOS camera device, a simple telescope and an electronic star map gadget.

Then Mike asked around the group to see what projects members were attempting this year. He said he wanted to see Cygnus X1 where the black hole was. Pete wanted to complete an image he has been trying to do for ages and Terry is going to complete his observatory. Someone else wanted to complete their observations of all the Messier objects.

Then Pete took us through the Google Earth programme and explained its workings. he showed close ups of his house.

The youngest new Moon it is possible to see, which occurs on May 27th this year was discussed.

Finally Dave showed a new programme he had found which allowed pictures taken with Digital Cameras and Digital SLRs to be dramatically improved.

Wednesday 31st May 2006

Colour and Computers Robin Cordell

Robin gave a very interesting talk on colour this evening.

Firstly, he explained how the eye worked. The eye works as a lens. Light comes in through the pupil, which acts as a lens and is projected upside down on the back of the eye. Here there are lots of receptors, which can be dived into two types, rods and cones. The rods deal with detailed vision, but only receive in black and white. The cones receive in colour, but are less detailed. The cones do not work at night so night vision is in black and white. The eye only sees in colour in its central area. The rest, along with the image inversion, is done by the brain, using a combination of scanning, memory and experience.

There is an area in the centre of the eye, which is only sensitive to colour and has no rods. This means at night, when you are looking at an image in the middle of your telescope eyepiece, you are using the least sensitive part of your eye for night work. This is why the technique of averted vision is used.

He went on to explain how colours are reproduced on printers and screens. There are two methods, the additive and subtractive. One uses the colours cyan, yellow and magenta in combination to make up all the other colours, the other uses red, green and blue. Mixing two of the primary colours in one system together gives you one of the primaries of the other.

Printers tend to use cyan, yellow and magenta, where as screens use red, green and blue. The two systems do not always represent the same colour in exactly the same way however. This is why a picture that looks good on screen can look disappointing on paper and vice versa.

There is an international standard agreed on the exact parameters of each shade of colour. It is impossible to print this off as an accurate colour chart and different peoples eyes may see these colours differently. However using the chart does ensure that things like traffic lights and road signs will always appear to be the same shade to you.

Printers and screens also cannot reproduce all of the colours, only a range of them. This is called a gamut. Screens are all adjusted to use the same gamut, but printers can very and may cover different colour ranges to screens. This is why pictures may not always print correctly.

Wednesday 7th June 2006

Cassini – Huygens Andrew Mowbray

I gave a talk on the Cassini-Huygens mission.

I described Saturn, the history of the name and known facts about the planet. I then described ho wit had been observed by Galileo, Cassini and Huygens. I went through the discoveries of the Pioneer and Voyager Missions.

I described the making, launch and journey of the probe including it using Venus twice, Earth once and Jupiter once for gravity assist. I described its arrival at Saturn and showed a video of the Huygens probe’s descent onto the surface of Saturn’s moon, Titan. I also played a sound track of its descent through Titan’s atmosphere.

I showed pictures of the ring system of Saturn and also showed pictures of and gave details on Saturn’s major moons. I showed a storm in Saturn’s atmosphere that had also been observed from Earth.

The evening ended with a short video that Sian had made for a language company that teaches English to foreign students using videos of teenagers describing their hobbies.

Wednesday 14th June 2006

Beginners/Observing Evening

As it was daylight, we held a beginners’ evening.

Terry showed us a PowerPoint presentation of the Southchurch Hall Open Day on the 4th June. It included pictures of the Sun showing halos.

I then did a short presentation on the Summer Moon illusion. This is when the Moon seems bigger when it is lower in the sky. It is not really and photographs prove this. There are lots of theories as to why this occurs, but know one is really sure.

Mike then did the evenings main presentation on asteroids. These small bodies orbit the Sun mainly between the orbits of Mars and Jupiter. Jupiter’s gravity makes gaps in the asteroid belts. They are believed to be the remains of a shattered or failed planet as they orbit where a planet should be.

Other asteroids, called Trojans, orbit the Sun, 60 degrees ahead of and behind Jupiter. Another group orbit the Sun near Earth and some actually have strange orbit around Earth.

Mike discussed their composition and sizes. He also mentioned how to observe the bigger ones. Asteroid 2004-XP14 will be coming within 1.1 lunar distances on the early morning of July 3rd and the Club has decided to try and observe it. Mike passed around the details.

Wednesday 21st June 2006

The Nebulae Part Three – Andy Turner

Over the last two years, Andy has been giving a series of talks on the various types of nebulae and their formation. Tonight in the third part, he discussed the life cycles of stars from birth to death and how many of these result in nebulae.

Some nebulae are clouds of gas forming into stars, such as the Orion nebula.

When a cloud of gas has collapsed sufficiently under gravity, it will start converting smaller atoms into bigger ones using atomic fusion. The by-product of this is a release of energy, which is what makes the star give out its heat and light.

A star like our Sun is mostly converting hydrogen to helium. When it runs out of hydrogen, it will start fusing bigger elements and will expand to a red giant. When this runs out of fuel, it will blow off clouds of gas and collapse to a white dwarf with a nebula around it. The Cat’s Eye nebula has undergone a similar process.

Andy gave much detail on the fusion lifecycles of different types of star and the physics and chemistry surrounding them.

Wednesday 28th June

Beginners’ Night

Terry showed some slides he had took using the Club’s solar scope of some prominences on the Sun and some rare sunspots. They are rare because the sun is so inactive at the moment. He then showed a picture of a 27 day old Moon. He wanted to catch a very old Moon after the discussions on the very new one recently.

Eddie then showed some pictures of globular clusters he had been taking recently to prove that the summer sky was not a complete dead loss. They were very good as usual, but it had taken him several nights to get enough image data to compile some of them.

Mike then expanded on the theme of globular clusters. He said they were large groups of usually very old stars, which orbit around our galaxy. Man of them do not orbit in the plane of the galaxy and can pas through it, although there is normally very little risk of collision, the two objects can exchange stars and other material.

Mike then mention the dark site observing for the coming weekend with the possible observation of a near Earth asteroid on the morning of July 3rd.

I then showed an image of Jupiter I had taken through my ETX-70 with web cam, which had come out rather well. There followed a brief discussion on weather patterns on Jupiter.

Wednesday 5th July 2006

Weather Satellites

Terry and I, assisted by Bruce gave a talk on receiving weather images from satellites and ground stations. We had set up radios, antenna and two laptops and projectors.

Terry introduced the subject and outlined why you would want to do it your self rather than rely on the BBC etc. He said the BBC could only do a general forecast for a wide area. If you need a specific forecast for say cloud in the Southend area, you need to work it out from your own data.

He then explained how charts and forecasts for up to five days could be received from the Fleet station at Northwood, west of London on shortwave radio using freely available software.

I then explained why Northwood used more than one frequency. This is due to an effect called propagation. Radio waves usually travel line of site and would usually go out into space, rather than follow the curvature of the Earth, so anyone over the horizon would not normally received them. Under certain conditions however, a charged layer of the Earth’s atmosphere called the ionosphere can reflect them back, allowing then to travel much further. This effect varies with the time of day, year and frequency used, so to achieve maximum coverage, several frequencies have to be used.

Terry then gave a demonstration of receiving weather charts from Northwood and Hamburg in Germany and interpreted their meaning. He explained how weather worked, how weather fronts occurred and how cloud, rain and wind are formed.

We then moved onto weather satellites. Terry described the effect of Doppler shift using video of a passing fire engine. The note of the siren changes as it passes. This is due to the movement of the engine compressing the wave as it approaches, making it a higher frequency, and stretching it as it goes away, making the frequency lower. Weather satellites do the same. As they pass they transmit on an apparently higher frequency and this lowers as they go away. This can lad to distorted images, but modem software, including the WX2IMG package, correct for this.

I then described polar orbiting satellites. These are usually in Sun-Synchronous Orbits. Several countries including Russia, France, and U.S. operate them and they can be accessed by anybody, anywhere in the world, as they pass over all of Earth several times per day or night. The U.S. operates them as ‘NOAA’, the National Oceanic & Atmospheric Administration.

A Sun-Synchronous Orbit is one that provides consistent lighting of the Earth-scan view. The satellite passes the equator and each latitude at the same time each day. E.g. the orbit might cross equator twelve times a day, each time at 15:00 local time. The orbital plane must also precess (rotate) approximately 1O eastward each day, to keep pace with the Earth's revolution around the Sun. Each orbit experiences about 30 minutes darkness and 72 minutes sunlight.

Polar orbiting weather satellites were first launched in the 1960s. Since then they have been made much more sophisticated and are very reliable. They exceed their expected lifetime by a factor of 3 in some cases.

The U.S. NOAA Polar Orbiters are in Sun-synchronous orbits with orbit altitudes of 500-540 miles (800-864km). NOAA 12, 14, 15, 16, 17, 18 and TIROS N are the ones currently in use. They use APT (Automatic Picture Transmission) and HRPT (High Resolution Picture Transmission).

To image, the early satellites used TV cameras. They now use a scanning radiometer. These scan back and forth as the satellite moves along its orbital track. It images the picture continuously and builds it up line by line.

I then explained Automatic Picture Transmission (APT). The Picture transmission is automatic and continuous. It uses solid-state sensors to give images similar to a standard photograph. It has two different light sensors, each with slightly different imaging characteristics. In addition to visible-light detectors, they also have a number of infrared (IR) sensors. IR sensors respond to heat and not light so IR cloud pictures can be obtained at night as easily as during day. The imagers give a resolution of 4.4km/pixel.

NOAA APT line-transmissions are at a rate of 120 per minute on VHF frequencies. Each line contains both visible and infrared data. The 1st half of each line-scan is IR data and the 2nd half is Visible-Light data. The quality of visible light images varies with time of day and seasons. They also relay search and rescue beacon transmissions.

I then showed some images that had been received from NOAA satellites of Europe, including some of the cloud of smoke caused by the Buncefield fire. APT images are greyscale, but false colour can be applied.

I then described High Resolution Picture Transmission (HRPT) images. These are transmitted in colour on UHF frequencies and have a 1.1km/pixel resolution. They need expensive and complicated equipment to receive them.

There are other polar orbiters. Russia launches polar-orbiting, not sun synchronous, satellites on an irregular basis. When operational they give very good low-resolution APT images, but they only last for a very short time. France has some sun-synchronous satellites, as does China with the Fengyun 1D/2B/2C satellites, which transmit HRPT on UHF. Japan has some GMS5 in sun-synchronous orbits transmitting HRPT only as well as relaying search and rescue transmissions.

I described the service status and history of the NOAAs and showed some diagrams and pictures of them.

I then described Geostationary Satellites. Their Orbit period is exactly equal to one sidereal day of 23 hrs, 56m 4.1s. Their trajectories are aligned with the Earth's equator. Any satellite in this orbit will appear as if it is always in the same place in the sky when observed from the same point on Earth. These orbits are at a distance of approximately 35,900 km (22,300 miles) from the Earth’s surface.

There are several geostationary weather satellites. There is the Meteosat operated by EUMETSAT at 0° of latitude, the GOES E (Geostationary Operational Environmental Satellite) operated by the USA at 75°W, the GOES W operated by the USA at 135°W, the GMS (Geostationary Meteorological Satellite) operated by Japan at 140°E and the Insat operated by India at 74°E. GOES-11 is kept stored in orbit as a spare. These cover the whole Earth between them.

They transmit very high resolution visual and IR images every 30 minutes. They are not available directly to very northern/southern latitudes. The images are very good quality, but due to their equatorial location there is a considerable amount of distortion. They are unable to show images in or near either of the Polar Regions. They have the advantage of a regular, same location, weather picture, which means that the track of any weather pattern is easier to see and predict.

They transmit weather fax/picture images on UHF only and require a dish or beam type antenna, expensive equipment and software for PC decoding. They spin on their axis at 100 rpm and a motorized- mirror with a period of approx. 20 minutes is used to provide vertical scanning. Un-like APT/Polar Orbiters, which transmit in Analogue form, these satellites transmit in Very-High-Density format. GOES 8/9/10/11/12 relay Search & Rescue Distress signals the same as NOAA. I then shoed some diagrams of GOES, showed some images and a brief run down of their history.

I then run the Satscape program on my laptop and projector. This showed the live track of NOAA 17, which we were going to download live pictures from. Terry then commenced the download on is laptop and projector so the audience could see the picture building up as my laptop showed the satellite moving long its tract.

We downloaded a reasonable infrared image of Europe with a lot of cloud cover and thunderstorms brewing, which Terry processed to enhance it.

Terry then finished off with some more images and explanation.

Wednesday 12th July 2006

Beginners' Night

Terry and I gave a brief account of our attendance at the St. Michael's Church fete on Saturday 8th July. Ed, Ted, Terry, Bruce and myself were all in attendance. We should some photographs we had taken of the fete. a halo round the sun and some shots through the solar scope of prominences on the Sun. Terry managed to win the raffle and get a bottle of champagne. I then read out a letter of thanking us for our attendance that had been sent by the organisers.

Mike then gave a report of a visit to the Dark Site on the night of 2nd/3rd July to observe the close approach of asteroid 2004XP14 which came within 300,000 miles. They had a superb nights observing, but did not see the asteroid, which was only visible in the morning twilight and so quite hard to locate.

The following night, it was further away, but overhead. Pete and Eddie imaged it form home, and both should an animation of the shots they took, showing it moving through the sky. They observed about 10 miles apart and did get some parallax between their images.

Andy then gave a talk about the search for how carbon is created in stars. In the 1920s, scientists such as Eddington had worked out how other elements were formed in stars by nuclear fusion, but could not find a satisfactory method for carbon 12. After the war, Fred Hoyle postulated a method involving enhanced carbon, but this particle had not yet been found. he persuaded the Caltech team to use their particle accelerator to make enhanced carbon and they eventually achieve it. It turns out that carbon 12 being produced in stars is quite unlikely and Hoyle, an atheist, said it looked like a "put up job", implying divine intervention.

Wednesday 19th July 2006

Dave Smith - Astro Quiz

Terry showed us some photographs that he took at the weekend of noctilucent clouds. These are clouds that appear high in the sky after the sun as completely set. They  are about 65 to 80 miles up in the atmosphere and so the sun's rays still catches them so they appear to glow in the night sky. Not much is known about them and how they form is still uncertain.

We then moved on to the main part of the evening, an astro quiz hosted by Dave. We divided into four teams and answered ten rounds of astronomy questions in various categories. it was quite light-hearted and a good evening was had by all.

Wednesday 6th September 2006

First meeting after Summer Break

The meeting opened with me giving details of the partial eclipse that was dune on 8/9/2006.

Terry then gave a PowerPoint show of all the photographs that had been taken over the summer at the Maldon Carnival, the crazy golf, the Chichester and the Kursaal Bowling.

Our stall a  the Maldon Carnival had several solar scopes including the Club one and Terry set up a weather satellite receiving station. We had many visitors and was busy all day.

Mike then showed some pictures he had taken with a webcam and a new diffraction filter which splits the light of a star into its spectrum. One of the images he took of a star contained similar absorption lines to a reference one obtained from the web.

Wednesday 13th September 2006

Beginners/Observing Evening

This was meant to be Beginners' Observing Evening, but instead we had to endure a very severe Thunderstorm and Torrential Rain while Mike gave a presentation including a complete rundown on the Clubs' (8)inch Newtonian Dobsonian telescope which was brought in - complete with its' spider inhabitant. (Notes by Terry as I was away.)

Wednesday 20th September 2006

Deanna Amos - Sun Stars & Constellations

Deanna presented a talk on Sun Stars & Constellations which was attended by an almost full house, even though some club members had already departed for and/or arrived at Kelling. In keeping with the norm, it was a perfectly clear evening for a presentation. (Notes by Terry as I was away.)

Wednesday 27h September 2006

Annual General Meeting followed by Beginners/Observing Evening

The A.G.M. was the usual brief meeting. The Committee were re-elected unopposed and thanked for their work during the past year which all agreed had been a good one. A discussion was held on Club equipment.

After the A.G.M., as it was cloudy, Mike gave a talk on the Coronado Personal Solar Telescope (PST). He showed the Hydrogen Alpha version that he had just bought. This type of scope only lets through a very narrow band of light frequencies at the red end of the spectrum These frequencies are given off by the hydrogen alpha particles in the sun. It allows prominences and flares to be viewed around the edge of the Sun. Prominences are huge outbursts of material, which sometimes fall back in loops under the magnetic influence oft he Sun. Filaments which are dark lines on the disk of  the Sun, are these features seen edge on.

Sunspots which are dark patches on the Sun's disk can also be observed. these areas are still very hot, but are cooler than the surrounding material so appear darker. They are also caused by magnetism.

Mike also described the Calcium K version which lets through light at the blue end of the spectrum and shows structure on the disk of the Sun.

Solar scopes normally costs thousands. Whilst is is a slight compromise, the Coronado PST gives good results for a few hundred pounds.

Wednesday 4th October 2006

Space Art - Jackie Burns

We met tonight at Southend Museum for a talk on space art by artist Jackie Burn. Jackie is one of the few space artists in Britain. She explained that there were three types of space artists, those that do pure fantasy pictures, which have no basis in reality, those who did pictures which could depicting reality, but are not scientifically researched, and those which are depict scenes that are real, or could be possible and are based on known science. The artist will take what is known and use the picture to perhaps speculate beyond this. Jackie belongs to this type. She reads and studies extensively to get the appropriate knowledge and inspiration for her work.

She had several of the works on display. These included images of the Moon, galaxies and impressions of what planets around other stars might look like. Some of them were more conceptual in nature. Pride of place was a quilt made of milar. She had obtained the material on a visit to a factory where they make satellites. Milar is used to cover the surface of satellites. She was given it in return for sweeping the floors at the factory.

She also tours schools and uses her art to get across astronomical and scientific principles. For example, she gets them to draw aliens and then explains the scientific principles behind what aliens may look like like.

It was a very good evening and gave a different insight into our hobby.

Wednesday 11th October 2006

Beginners/Observing Evening

At 7:30pm the sky was clear, but by 7:35 it had clouded over completed so we retreated in doors. Mike talked about the Astro Camp at Kelling Heath in Norfolk. He mentioned that some CPAC members had been filmed or interviewed by the BBC' "Sky at Night" programme. He showed a short video clip from the last programme that included some of this footage. He then showed some pictures taken at the  He showed the wide range of scopes that can be seen there and also showed how wet it had been.

Pete mentioned Comet Swan that can currently be seen in the evening sky.

Ted then gave a demonstration of his 6" Newtonian reflector telescope. He assembled it and then explained how it worked. he then took out the main mirror to demonstrate how to clean it.

Wednesday 18th October 2006

The Moon - Mike Culley

This evening was originally going to be a talk but Chris Lintott, but due to circumstances beyond our control, this had to be postponed. We still met at the Southend Museum as planned and Mike leapt into the breach and gave us a talk on the Moon.

He went through early observations of the Moon, including spurious ones of roads, bridges, oceans and inhabitants that some people once believed they could see there. He also described the more scientific observations that has been made over the centuries.

He briefly described each of the Apollo Moon missions, indicating where they had landed and what each one had achieved. This included a brief video of a Lunar Module being unloaded from its crate at the Kennedy space centre.

Finally he handed round some samples of meteors and Moon rock which were currently on loan to the Museum.

Wednesday 25th October 2006

Beginners/Observing Evening

It was cloudy this evening so I did a talk on the David Dunlap Observatory (DDO) which I had visited in September whilst on a holiday to Canada. It is located at Richmond Hill in the suburbs of Toronto in Ontario.

The observatory was the brainchild of Dr Clarence A. Chant (1865-1956)He is know as the "Father of Canadian Astronomy”. In 1905 he established a Department of Astronomy at the University of Toronto. He wanted to build an observatory, but could not get any funding. In 1921 he gave a lecture on a comet and  a rich businessman called David Alexander Dunlap was in audience. He got the astronomy bug and agreed to finance an observatory.

Unfortunately he died in 1926. His widow Jessie Donalda Dunlap was approached to build the DDO as a memorial to her husband and she agreed. The site chosen was a farm 25km (15.6 miles) north of of the University  of Toronto campus. It was constructed between 1930 and 1935. The telescope and dome were made by Grubb-Parsons in Newcastle and shipped from England in 1933. The Pyrex mirror was cast at the Corning Glass Works in the U.S. in 1933. They were then shipped to England to be ground and polished by Grubb-Parsons between 1933-1935. The dome and telescope were reassembled on site by the Dominium Bridge Company.

It was opened on May 31st 1935 (Chant's 70 birthday). When built the 1.88 m telescope was the second largest in world after Mount Wilson. Later, two other reflector telescopes (0.5m and 0.6m) were built on top the of Administration building. A 6” refractor from the old Toronto Met Office was also installed here.

It is a 74” (1.88m) Cassegrain. It s moving parts weigh 25 tons (23 tons without  the mirror). The Mirror weighs 2 tons and is 1’ (30cms) thick. The tube is 30’ (9m) in length. Its external diameter is 7’(2.1m). The dome is 61’(18.5m) in diameter and weighs 80 tons.  It has two 4” refractor visual finderscopes and one  6” refractor CCD finderscope. It has two spectrographs attached to it. it is now used for student projects, training and for outside parties to do research on. Due to light pollution form Toronto which has grown up around it, most of the observatories work has moved to Chile.

I showed various pictures of the inside and outside of the observatory, the telescope and other equipment. This included a picture of the sidereal motor drive which is a washing machine motor!

Wednesday 1st November 2006

Pinhole Cameras - Ron Mansfield

This was a updated version of a talk Ron had given to CPAC back in 2003. A photographic competition was proposed by the Club a long while ago to find the taker of the most unusual photograph. Ron said he had long been fascinated by pinhole photography and decided to us it to try and take an unusual picture of an object in space. He said he had decided to concentrate on the Moon, as it had to be bright and big. The Sun did not have sufficient surface detail. He showed us a wonderful home made camera, which used 120 film. It was 400mm focal length with a pinhole of 0.65mm. The camera was made entirely of cardboard. He showed us this camera and it was quite impressive. The image of the gibbous moon however was disappointing. It was small & lacking definition.

Ron decided  that as he clearly needed more focal length so he would extend the camera. This time it was 1000mm with a 0.95mm hole. To achieve this he made an extension to the cardboard tube. He got this out and added to the camera he had already shown us.  This time the image was bigger with a more detail so he decided to extend it again. He added another extension tone was 2m long with a 1.94 hole. Te added this to the camera and it was now starting to extend down the aisle of the church with Terry holding the other end. The image was bigger but still fell short of being good.

He then extended it 4m with a 2.7mm hole. It was now well down the aisle with Mike and Ted helping to hold it up. Ron showed a picture taken with a normal camera of his latest try mounted on Ted’s 16inch to provide guidance and support for the first 6 feet or so. At this length the shutter release, which was at the front end, was difficult to reach so Ron had devised a remote shutter release, which was impressive in its own right. The results this time was bigger again but still failed to show craters.

He then brought out an extension that took it to 7m. This was so long it drooped despite e being made from special thin card. so cantilever device that attempted to hold up the front end was used. Despite this, it did not work very well due to it bending and being impossible to line up with the film. Ron in its defence said that one reason for the problems was that the cantilever support could only work in one plane so it would start off OK but as the time exposure progressed the 16inch of rotated in two planes thus causing the cantilever to be offset. So it was back to the drawing board.

He realised that a change of direction was required so he decided to fold the camera up by adding 2 mirrors. He showed camera, which had a focal length of 6.8m. It was much more robust and compact compared to the 7m. The image of the moon was larger,  but still not of sufficient quality. Ron also showed a picture of Jupiter, which required a 20 min exposure and was a fuzzy blob.

Ron then moved to another field of pinhole photography. This was a pinhole mirror. It was a piece of optical flat mirror blacked out, but with a clean pinhole in the middle. This was mounted on a plug in domestic timer such that the mirror was mounted on the bit that rotates. This arrangement allowed the mirror to track the sun. He had projected the sun into his bedroom, which was a distance of 70 feet. He had a photo of the image which for reality purposes had an edge clipped by the curtains..

Ron then showed an MPP 5x4inch large format camera. He had replaced the lens with a pinhole. He showed a portrait picture of Ted, which had required him to not move for 70 seconds.

Ron then showed us a pin hole camera he built to take a 130 degree panoramic. The results were really very good. We saw Ron’s old factory site and several images of a star camp at Thetford in 200l.

The next attempt was for three 120-degree panoramics taken simultaneously with a single camera.  The picture was another from Thetford, which Ron showed as individuals and then put together in Photoshop.

Ron then showed a 360degree panoramic shot which was taken by a pinhole device that directed the light through a vertical slot which was rotated exposing the film which was mounted on the inside surface of a drum. An old tape recording machine provided the power for the rotation via an intricate series of pulleys and belts. One rotation took about 90 seconds. He showed two photos of his factory site.

Ron’s penultimate camera was a stereo pinhole camera which gave very good results. Ron showed the pairs of images on screen, which if viewed from directly in front would merge to form a 3D image. I have funny eyes so didn't work for me, but there were wows from the audiences who were crossing their eyes to view. In case this wasn’t enough Ron had made a viewer, which did work for me, again of course from cardboard, into which the prints could be placed to be seen in all their glory.

The final camera he showed was a 20 x 16inch large format one. This one just couldn’t manage with 120 film so Ron had to use bromide paper.  Ron showed several pictures and the best were some pictures of a beautiful old American car, which was nearby to his factory. It demonstrated so well the ability of pinhole camera to have incredible depth of field. The camera had been positioned about 2feet from the car but it was all in perfect focus.

All the cameras had been made from cardboard and odds and ends for next next to nothing, but were very well engineered. Proof, if any were needed that astronomers are not eccentric in any way.

Wednesday 8th November 2006

Beginners/Observing Evening

As usual it was cloudy so we had a beginners' evening. This was in two halves. In the first half. Mike gave us a warts and all talk on his Meade ETX-125 telescope. He had originally bought an Meade ETX-105 which is the smaller version. It was a new one, but when it arrived, it was broken so he returned it. The second one he got had one of the holes that you need to attach it to the tripod missing!

After returning it, he upgraded it to the ETX-125. This wad fortunately intact and working. It came with a hand controller, but he also go the Autostar for it. He demonstrated the alignment procedure for it and said that it can occasionally play up during alignment.

It gives good views of planets, double stars etc, but is not quite so good on faint fuzzies. It is however light and portable and easy to use. It runs off of pen cell batteries which it eats and is best used with an external power supply. Bits do have a tendency to drop off and he has had to stick a few back. Recently he dropped the Autostar and it stopped working. He took it apart and found there was a capacitor inside which had never been soldered in and this had fallen out. He put it back and soldered it in properly. It now works again. In summary, it is a good scope, but check you have not got a Friday afternoon job.

After the tea break, Dave took over. First he showed us a time lapse photography film he had made of some tulips in a bowl reviving after they had been watered. Then he showed us some astro pictures he had taken at Kelling Heath with a digital SLR using a macro lens. These had come out very well.

Finally he said that a new version of the Virtual Moon software was available and he showed us some domes to look out for near the Moon's terminator in the next few days.

Wednesday 15th November 2006

Modelling the Tidal Tails of the Sagittarius Dwarf Galaxy -- What Shape has the Halo of the Milky Way ? - Dr. Michael Fellhauer

Tonight we had a visit from an external speaker. Dr. Michael Fellhauer gave us a fascinating talk on the work he is doing on modelling how the dwarf galaxies that orbit the Milky Way behave.  He explained that he is  not an observing astronomer, but a computer modeller who works and tries to explain the behaviour of the cosmos. The nearest is the Sagittarius Dwarf Galaxy. This is hidden behind the core of the Milky Way and is very difficult to detect. Digital analysis of deep sky surveys have recently reviewed it.

He described the Milky Way has consisting of a central core of stars, a disk of stars and an outer halo consisting of thinly spread stars. Many of the halo stars are collected by the Milky Way pulling them off dwarf galaxies as the orbit. They leave behind tidal tales of stars which spread for vast distances through the halo. These have been observed using the above techniques and he was asked to come up with a computer model which explains it. The Sagittarius Tidal Tails are quite complex as it has up to four of them.

He worked on the computer model which required a lot of computer processing time and programming. Eventually he come up with one that fits. This also indicates that the halo is very nearly round. We also had a brief discussion about dark matter and gravity waves.

He made what was a very deep subject very accessible and it was a very enjoyable evening.

Wednesday 23rd November 2006

Beginners/Observing Evening

As it was cloudy we held a beginners' evening. We started off with two pictures of the Moon which had been taken by Bruce by just holding his camera to the eyepiece of his telescope.

Then Pete showed us some images of Mayall II a globular cluster which orbits the Andromeda Galaxy. This is a quite a challenge to observe and photograph so well done to him.

I then gave a talk on the Planet Mercury. First I defined a planet. I got everyone to look at the floor and said they were all observing one, the Earth. I showed where the Earth fitted into the traditional solar system of nine planets orbiting the Sun. I then said that due to the discovery of new objects, Pluto had been reclassified as a dwarf planet.

Mercury is the closest planet to the and is the smallest of the “proper” planets. It is slightly smaller in diameter than Ganymede and Titan, but more than twice as massive. Its average orbital distance from the Sun is 57,910,000 km (0.38 AU). Its diameter is 4,880 km and its mass is 3.30e23 kg. Its gravity is 0.38g. I then showed a diagram comparing its size with the other terrestrial planets.

It has been known since at least time of the Sumerians (3rd millennium BC) The Greeks gave it two names, Apollo for its apparition as a morning star and Hermes as an evening star. They knew, however, that both names referred to the same body. Heraclitus even believed that Mercury and Venus orbited the Sun, not the Earth.

In Roman mythology Mercury is the god of commerce, travel and thievery. He is the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across sky.

In 1610 it was observed by Galileo. In 1639 Italian astronomer, Giovanni Zupus discovered it circled the Sun. In 1841 the German astronomer, John Franz Encke made 1st mass determination using the gravity effect on comet Encke. Between 881-1889, Giovanni Schiaparelli made the first map of Mercury's surface features.

It has a highly eccentric orbit. At perihelion it is only 46 million km from the Sun. At aphelion it is 70 million km. 19th Century astronomers made careful observations of the orbital parameters but could not adequately explain them using Newtonian mechanics. Tiny differences between observed and predicted values were a minor but nagging problem for many decades. It was thought another planet (sometimes called Vulcan,) slightly closer to the Sun than Mercury might account for this. Vulcan was never found however as it did not exist.

The real answer turned out to be much more dramatic. It was Einstein's General Theory of Relativity! Its correct prediction of motions of Mercury was an important factor in the early acceptance of it.

Until 1962 it was assumed "day" was the same length as "year". This was shown to be false in 1965 by Doppler radar observations made in US by Gordon Pettengill and Rolf Dyce who measured the rate of rotation. Using radio telescopes the measured temperature of night time side was found to be too warm for it not to rotate. I then explained how the Doppler shift worked.

Mercury rotates three times in two of its years. It is the only body in the solar system known to have an orbital/rotational resonance with a ratio other than 1:1 although many have no resonances at all. One rotation is 58 days. One “day”, sunrise to sunrise is 176 days. One “year” is 88 days. Temperature variations are the most extreme in solar system ranging from 90 K to 700 K.

In 1968 Surveyor 7 took first spacecraft picture of Mercury from the Moon. Mariner 10 surveyed Mercury in flypasts in 1974 and 1975. It mapped 45% of the surface. It was very similar to the Moon, heavily cratered and very old. The surface has enormous escarpments, 100s kms in length and up to 3km high. They cut through craters and other features indicating they were formed by compression. The surface area shrank by about 0.1% or a decrease of about 1 km in planet's radius.

I then showed an image of the Antoniadi Ridge. This is 450 km (280 mile) long  and transects a large 80 km (50 mile) crater about half way along.

The Caloris Basin is the largest surface feature. It is about 1300 km in diameter. It is thought to be similar to the Moon’s maria. Like these, it was probably caused by a very large impact early in its history. The impact was probably also responsible for odd terrain on the exact opposite side of the planet. The shock wave produced by the impact may have been reflected and focused here .This jumbled the crust and broke it into a series of complex blocks. The area is about 800 km (497miles) on each side.

It has regions of relatively smooth plains. Some may be the result of ancient volcanic activity but some may be result of deposition of ejecta from cratering impacts. Reanalysis of the Mariner data give preliminary evidence of recent volcanism. Radar observations of the North pole which was not mapped by Mariner 10, show evidence of water ice in the shadows of some craters.

It is much denser than the Moon. It is the second densest major body in the solar system, after the Earth. It has a large, dense iron core, probably comprising the majority of the planet. The core radius is 1800 to 1900 km. It has only a relatively thin silicate mantle and crust, 500 to 600 km thick. At least some of the core is probably molten.

It has a very thin atmosphere consisting of atoms blasted off surface by solar wind. Mercury is so hot, these atoms quickly escape into space. In contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly being replenished. It has a small magnetic field whose strength is about 1% of Earth's. Mercury has no known satellites

I then mentioned the MESSENGER probe. This stands for Mercury Surface Space ENvironment, GEochemistry, and Ranging mission. It was launched on August. 3rd , 2004 and will arrive at Mercury on March 18th 2011.

I then discussed observing Mercury. It is tricky to observe as it is usually a day time object. It can be observed when at it is at eastern or western elongation from the Sun, during a total eclipse or during a transit. At western elongation it is visible before sunrise and at eastern elongation it is visible after sunset. Also its orbit can be tilted anywhere between 18 and 28 degrees above the plane of the Earth's. When it is at 28 degrees it rises much higher above the horizon. Mercury also shows phases like Venus or the Moon does.

It is observable between 14/11/06 and 14/12/06. It is at its greatest elongation west on 25/11/06 when it rises two hours before the sun does.

I gave the warning to never look directly at the Sun. When observing Mercury with a telescope or binoculars, only attempt to do so when the whole of the Sun's disk is below the horizon. As Mercury lies close to the Sun in the sky there could be a danger of getting the Sun in the view. This could result in eye damage or loss of eyesight.

I then discussed the Transit of Mercury on Wednesday 9th November 2006. A transit is defined as "The passage of a celestial body across the observer's meridian.” or “The passage of a smaller celestial body or its shadow across the disk of a larger celestial body.” (Google).

The first observation of a transit of Mercury was on November 7, 1631 by Pierre Gassendi. Other notable transits include May 3rd 1661 which was the day of the coronation of King Charles II. It was observed by Christiaan Huygens in London. On November 9th 1769 it was noted that Mercury had little or no atmosphere during  a transit.

Why watch one? For most, it is something interesting to observe, but researchers at the University of Hawaii's Institute for Astronomy used this transit to measure the amount of sodium in Mercury's tenuous atmosphere, measure its altitude, and determine how it varies from Mercury's pole to its equator.

I then showed some images of the transit which was not observable in the UK as it was after sun set.

Transits of Mercury can happen in May or November. November transits occur at intervals of 7, 13, or 33 years. May transits only occur at intervals of 13 or 33 years. The last three transits occurred in 1999, 2003 and 2006. The next transit of Mercury occurs on 9th May 2016. It is  visible from the Americas, Europe, Africa and central Asia.

Wednesday 23rd November 2006

Trials and Tribulations with Ted Rodway

Tonight was a two part evening, hosted by Ted. In the first part Ted showed us that not everything always go to plan when you go observing. He showed us pictures of his first Tasco telescope, which largely fell to bits. He then bought a BC&F 6" F^ Newtonian Reflector to sue for astrophotography. He soon realised that you need a sidereal motor drive as well. He also had to reposition the mirror to be able to focus it.

He then went for a 16" setup in his observatory which did not improve things that much as the field of view was too small still. Finally he hit a combination that worked.

He then mentioned ,and showed cartoons he had done, of various observing evenings held at Danbury. On one occasion, Brian scared off all the couples in the nearby lovers' lane by flying a kite with a big skeleton on it and shining a torch up on it to light it up. On another, Ted dropped his eyepiece on the grass. he picked up something long dark and cylindrical, only to find it was a message left by one of our canine friends!

He went to Turkey this year to see the total solar eclipse and take pictures of it. When he got there he found he had not taken any film. He managed to purchase some roles of Kodak 200 Gold. he had planned to take 72 exposures on two roll of 36 exposure film and had drawn up a schedule of images. He then found he had two rolls of 24 exposure film!

He wanted to have his camera's motor drive working during the eclipse, but it refused to play ball. Afterwards he found he had not set it up quite right. He did get some good images though.

Ted goes to the observatories on the top of the mountains in Las Palma in the Canary islands to take images above a lot of the atmosphere. When he went on one occasion, it snowed and they were cut off for most of the week. He showed us a suspect snowman that they made.

After the break, Ted showed a video demonstration with commentary of how to use the Registax programme.

Wednesday 6th December 2006

Observing & recording the winter night sky with Pete Carson

I was away for this one, but Terry reports that Pete put on excellent presentation, both in the way he presented as well as many superb images of various 'observations of the winter sky'. He showed various nebulae, clusters and other deep sky objects which kept the audience engrossed.

Wednesday 13th December 2006

Beginners/Observing Evening

As it was cloudy we held a beginners' evening. Andy Turner gave us two talks.

The first was called "Oh for a bright, shiny galaxy". He posed the question, how close would the galaxy M33 have to be before it appeared as it does in good astrophotos? The answer is, it never would. He showed the maths and proofs that surface brightness does not increase as you get nearer to an object. For example if you are standing 2m from a wall, it reflects light and appears to be a certain brightness. if you close in to .5m of the wall, it gets no brighter. If we go closer to M33, it would fill more of the sky, but get no brighter.

His second talk was called, "Oh for a bright shiny meteor". He read an account by Mary Fletcher FRAS from her 1939 book "Everyman's Astronomy" in which she described the November Leonids display through the centuries, especially the spectacular displays of 1833 and 186 where over 25,000 meteors an hour were seen.

All in all, two very interesting talks.

Wednesday 20th December 2006

Christmas Social Evening

As it was reasonable clear some of us took binoculars and telescopes outside and did some observing. It was very cold and freezing damp, but we saw some objects. Then it was inside the church hall for drinks and nibbles to end the year.

Merry Christmas and a Happy New Year to all!


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