Castle Point Astronomy Club
Castle Point Astronomy Club Diary
July 2018 by Dave Stratton
Castle Point Astronomy Club


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Wednesday 4th July 2018

Mike reminded us that we have a Family Day at Hadleigh Castle Country Park on 28th.

Next week we are juggling the schedules as there is a risk that a certain football team may be playing so Nick James has been moved to the following week and we have pulled Ed forward.

Ted said that the church fete is on 14th.

Mike introduced Andrew for his talk: The Astronomer´s Guide to Strange Things in the Sky

He began by saying that UFO means Unexplained Flying Object – so not necessarily something alien - just something unexplained. He defined the various ways we can be confused. Most things seen in the sky are lights of some sort.

He said that a major problem was gathering the story from witnesses: - Where, when, what, size, state-of-mind. It was very difficult. He then told a story to illistrate state of mind. It involved going back to the year 1977.

The public had been becoming more interested in UFOs for several years before. Chariots of the Gods? Unsolved Mysteries of the Past is a book authored by Erich von Däniken came out in 1968. It involves the hypothesis that the technologies and religions of many ancient civilizations were given to them by ancient astronauts who were welcomed as gods. This book, which is pure fiction but remains a very good read did a lot to get the public thinking about aliens.

Close Encounters of the Third Kind is a 1977 American science fiction film written and directed by Steven Spielberg, and starring Richard Dreyfuss, Melinda Dillon, Teri Garr, Bob Balaban, Cary Guffey, and François Truffaut. It tells the story of Roy Neary, an everyday blue-collar worker in Indiana, whose life changes after an encounter with an unidentified flying object. Close Encounters was a long-cherished project for Spielberg. A wonderful film that added to the imagination of lots of people.

Andrew said that as a youngster he lived near Chingford. Pole Hill was a local bit of higher ground that was often the location of UFO reports. Lights had been seen ascending into the sky and also landing on the lcoal reservoir before disappearing beneath the surface. A watch was planned by the local paper, on Pole Hill which is on the Greenwich Meridian on a Saturday night in early August fo that year. Andrew was there, but the aliens were not! Locals gathered on the hill and a couple of eccentrics approached asking for directions to the nearest pub. Andrew asked if they didn't want to wait in case any UFOs appeared. They replied that they always saw them far better when they came out of the pub!

He said that natural objects like the Moon, Venus, Mars, Jupiter and Saturn can often cause concern and a special one is the moon in eclipse when it becomes red! Meteors are another common sighting and of course comets such as Hale Bopp.

Comet Hale–Bopp is a comet that was perhaps the most widely observed of the 20th century and one of the brightest seen for many decades. Hale–Bopp was discovered on July 23, 1995, separately by Alan Hale and Thomas Bopp prior to it becoming naked-eye visible on Earth. Although predicting the maximum apparent brightness of new comets with any degree of certainty is difficult, Hale–Bopp met or exceeded most predictions when it passed perihelion on April 1, 1997. It was visible to the naked eye for a record 18 months, twice as long as the previous record holder the Great Comet of 1811. Accordingly, Hale–Bopp was dubbed the Great Comet of 1997.

Comet Holmes is a periodic comet in the Solar System, discovered by the British amateur astronomer Edwin Holmes on November 6, 1892. Although normally a very faint object, Holmes became notable during its October 2007 return when it temporarily brightened by a factor of about half a million, in what was the largest known outburst by a comet, and became visible to the naked eye. It also briefly became the largest object in the Solar System, as its coma expanded to a diameter greater than that of the Sun.

Andrew said that the Northern Lights were rarely seen at these latitudes, but if the faint green glow is seen it can look weird. We saw a diagram with which he explained how our magnetic field largely deflects the solar wind around the Earth, but some is funneled down at higher latitudes.

A sun dog or mock sun, formally called a perihelion in meteorology, is an atmospheric optical phenomenon that consists of a bright spot to the left or right of the Sun. Two sun dogs often flank the Sun within a 22° halo. The sun dog is a member of the family of halos, caused by the refraction of sunlight by ice crystals in the atmosphere. Sun dogs typically appear as a pair of subtly colored patches of light, around 22° to the left and right of the Sun.

Geese can sometimes look red as the sun strikes them from below in the late evening.

Lenticular clouds are caused by uneven ground formations can look like giant flying saucers.

Mirages are another common cause when distant objects – even cities can appear upside down or the right way up - these are caused by layers of air at different temperatures.

St. Elmo´s fire is a weather phenomenon in which luminous plasma is created by a coronal discharge from a sharp or pointed object in a strong electric field in the atmosphere. St. Elmo´'s fire is named after St. Erasmus of Formia, the patron saint of sailors. The phenomenon sometimes appeared on ships at sea during thunderstorms and was regarded by sailors with religious awe for its glowing ball of light, accounting for the name. Sailors may have considered St. Elmo´s fire as a good omen.

Ball lightning is an unexplained and potentially dangerous atmospheric electrical phenomenon. The term refers to reports of luminous, spherical objects which vary from pea-sized to several meters in diameter. Though usually associated with thunderstorms, the phenomenon lasts considerably longer than the split-second flash of a lightning bolt. Many early reports claim the ball eventually explodes, sometimes with fatal consequences, leaving behind the odor of sulfur. Andrew said that a relative of his had a scorch mark on a wall that was caused by this phenomenon!

Manmade objects get a look in too: - Stealth bombers like the B2 and F117 as when they were first seen they were secret – who knows what is secret today? Aeroplane contrails can be puzzling, aluminized balloons, hot air and weather balloons and of course air ships.

Fireworks and distress flares – some have parachutes so stay ‘still’.

Satellites like the ISS which can be seen daily at various places and iridium flares which are common but it is rare to see them accidently.

Chinese or Thai lanterns can look very odd floating along especially if there are lots of them. Laser beams and searchlights confuse.

Andrew returned to the Chingford story to finish. He researched the matter and discovered that rockets were being launched from a local research facility and also top secret submarine models were being tested in the large reservoirs in the area at night!

The Truth is Out There

Wednesday 11th July 2018

We had a splendid start tonight as Ed handed out loads of chocolate to all present which was only slightly down due to some game or other on the box.

Mike reminded us that on on the 28th July we has our first Space Day and those invovled should get there for 09.30 and it would run until 16.00.

He said that a celebration of the club´s 50th birthday was planned next April. The BAA is helping. Volunteers will be required.

Ted said that this Saturday was the Church Fete.

Andrew said that next week we have Nick James with a talk about Meteors and Fireballs.

Peter said he had a DVD with a very good film for anybody to borrow.

Mike Introduced Ed for his talk:- Observing Highlights for July and August

He told us that Mercury reached its greatest eastern elongation on 28th August and it will be visible in the mornings while Venus would reach its greatest western elongation on 17th August and be visible in the evenings. Saturn is just past opposition. It´s low, but improving in the South East in the evenings. Jupiter remains good in the South West in the evenings.

On 27th July we will be treated to a Lunar Eclipse. The Moon will rise at about 20.50 in eclipse and totality will end at 22.10. Ed said he will be on the cliffs at Leigh-on-Sea about 20.30 to see when it will rise from the sea at that location. Several people said they would join him.

Mars is opposition on the same day very close by. This approach of Mars is close so it will appear larger. Ed showed us with the aid of a diagram how as the Earth overtakes Mars it causes Mars to appear to move backwards in the sky – retrograde motion - tracing an ‘S’ shape against the sky.

He showed us a star chart with Mars´ position plotted and said it would appear to be stationary in July and September.

He said he had seen the 2003 opposition from an excellent site; he did some sketches in 2007 which he showed to us.

We saw a chart showing the positions of the Martian moons in 2003. He had been at Kelling heath and saw Deimos through the Club´s 16 inch on 3rd August.

Ed showed us a star chart and pointed out the Summer Triangle of Deneb, Vega and Altair, he said the area is rich in things to look at. Such as M39 and 61 Cygnii. He pointed out their locations on a chart.

M39 is an open cluster in the constellation of Cygnus. It was discovered by Charles Messier in 1764. M39 is at a distance of about 326 pc from Earth whose age is estimated to be from 278 million years. It contains about 30 stars. He added that it was a bit of a mystery as to why Messier included it as its does not look like a comet at all.

61 Cygnii is a binary star system in the constellation Cygnus, consisting of a pair of K-type dwarf stars that orbit each other in a period of about 659 years. It isn’t among the brightest stars. In fact, it takes some effort just to find it, because it is not much brighter than the faintest stars visible to the unaided human eye. It is, however, among the most important of stars visible without optical aid. It has one of the largest proper motions – that is, sideways motions along our line of sight – of any star in our sky. Its large proper motion has given 61 Cygni the nickname Flying Star.

It was discovered by Fred Bessel and was the first star to have its distance measured. It is 11.4 light years away.

Ed showed us a chart with his own drawing of the star´s changing position in 2014, 15 and 16.

Ed said the stars Tarazed and Alshain bracket Altair. To the East of Tarazed is the Triple Cave Nebula, it appears to have the shape of an ‘E’ as it masks the background stars. It is six Moon diameters from Altair. Ed said the image was taken by Barnard in 1905.

He finished with a map of Burnham-on-Crouch showing the location of the station as this is where we meet for trips to our Dark Site. He told us a tale about a trip there in the rain and cold a while ago when the Zapper (to open the gate) would not work until they robbed his car key of its battery. Despite the weather Peter’s phone´s weather app showed a clear window so they stayed and were rewarded with a splendid display of meteorites.

Excellent as usual.

Wednesday 18th July 2018

Andrew said that this was our last scheduled meeting until 5th September. We will however be meeting up in the usual pub.

Ed said that next Friday 27th we would have a lunar eclipse watch – he will circulate the details.

Ron said the Club´s solar scope needed a new filter.

Peter said there would be a club event to mark the Perseid meteor shower on 13th August - details to be circulated.

Mike said the Family Space Exploration Day at Hadleigh was on 28th July.

Mike introduced Nick James for his talk: Meteors and Fireballs

Nick began with a comet image – explaining that comets are the cause of meteors. As they orbit the Sun they leave a trail of fragments along their path. If the Earth passes through the track the fragments hit our atmosphere and burn up.

Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called ‘shooting stars’ or ‘falling stars’, although they are not stars at all. Meteors are caused by the entry of small pieces of rock, dust or metal from space into the atmosphere at extremely high speeds. These particles, called ‘meteoroids’ when they are floating around in space (think of very small asteroids), are travelling at incredible speeds of tens of kilometres per second (tens of thousands of miles per hour) when they streak into the atmosphere. The incredible pressure meteoroids experience when they collide with Earth's atmosphere shatters them, transferring energy to atoms and molecules in the atmosphere, which then release the energy by glowing. This glow produces the bright trails of light in the sky we see as meteors.

From a meteoroid to a meteor and meteorite: how a meteoroid enters the atmosphere to become visible as a meteor and impact the Earth´s surface as a meteorite. A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids and range in size from small grains to 1 metre-wide objects.

A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate that energy. It then becomes a meteor and forms a fireball, also known as a shooting star or falling star; astronomers call the brightest examples ‘bolides’. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create a crater.

A meteoroid is a small rocky or metallic body in outer space.

Meteoroids are significantly smaller than asteroids and range in size from small grains to one-meter-wide objects. Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.

When a meteoroid, comet, or asteroid enters Earth's atmosphere at a speed typically in excess of 20 km/s (72,000 km/h; 45,000 mph), aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it leaves in its wake. This phenomenon is called a meteor or ‘shooting star’. A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, it is then called a meteorite.

An estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earth´s atmosphere each year.

He said sporadic meteors could be seen at any time – they appear randomly from any point in the sky whilst with a specific shower the track of each meteor will always converge on a single point. Showers such as the Perseids and the Geminids are named from this location.

The best period for showers is August to December.

Nick said that if an individual meteor was observed from different places then its trajectory can be established.

We saw a chart showing lots of passes of the Comet 109P Swift Tuttle – the origin of the Perseids.

Nick spoke of J P M Prentice who collaborated with George Alcock in the 1930s to study meteorites.

We saw his image of a Perseid taken in 1975 and a pic of the film camera that he used. A later image of a fireball taken with a Practica 35mm camera.

When a meteor hits the Earth´s atmosphere at 35Km/sec it decelerates to zero in a few seconds - it is this friction that causes the brightness that we see.

We saw a pic of John Mason and Patrick Moore with a device John had made that used 6 cameras pointing up with a rotating shutter that interrupted the light source in a precise way. This enabled the track of any meteorites seen to be measured.

We saw a pic of Nick´s Canon T70 and the train left by a fireball after the trail has gone – the train could be seen to be distorting in the air.

We saw an amazing image from a Leonid shower of 20,000 meteors/hour with 17 meteors and a fireball caught.

He said that Digital still imaging cameras are much more sensitive so allow much faster exposures allowing for better accuracy when measuring.

We saw a wonderful fireball taken on 21(sup>st September 2012. Another two images of the same fireball taken at different locations allowed very accurate measurement.

Lots of similar images have been gathered and analyzed - all taken by amateurs.

We saw an amazing map of UK showing the path of a meteor as it travelled from West of Denmark to West of Eire. Nick said it was probably 30/40cm across - it actually bounced out of the atmosphere and probably came down again in the Pacific.

The Chelyabinsk meteor was a superbolide caused by an approximately 20 metre near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT, with a speed of 19.16 ± 0.15 kilometres per second. It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball. Nick said that this event was recorded by lots of dash cams as they are very common in Russia.

He said modern black and white cameras can take images at 25 per second.

He said that he has two set up at his home and we saw a video showing lots of meteors taken by one of his cameras.

He uses software called UFO System and also UFO Analyzer software. It uses the background stars and can collect data all by itself. There is also UFO Orbit software which can calculate orbits in a few minutes.

He showed us a slide with his data from Chelmsford and data from Wilcot with seven cameras showing a mass of orbits.

An amazing image showing layers of orbits surrounding Earth.

Yet another incredible image of meteor orbits colour coded to indicate their velocity around Earth. Most data comes from the Northern hemisphere.

He said that Radio Telescopes and Spectroscopy are increasingly used to study meteors.

We saw an image of a fireball that was brighter than the full Moon whose train lasted over three minutes.

Radio transmissions from Graves in France are used. Diffraction gratings allow spectrographic analysis of meteors.

He said the Sony A7S camera was excellent. He used it to look at the night sky from his garden and the quality was amazing even the Milky Way could be clearly seen.

We saw a video of meteor complete with its train - working at ISO 12,000 it captured the track with a green colour.

Hi finished with a stacked image of the Perseids showing that they did indeed come from a single radiant.

Excellent.

Wednesday 25th July 2018

No meeting.


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