January’s talk

The Stan Cocking Memorial Lecture: Comets, Ferrets and Nebulae: Charles Messier and 18th Century Astronomy presented by Dr. A Chapman.

For those of you who are interested in the life and achievements of Charles Messier (1730-1817), you can easily do a search on the www, but you know that a talk on the subject by our local luminary, Dr Allan Chapman, is not going to be run of the mill.
When Charles Messier appeared on the scene, comets were still very much mysterious and misunderstood. They were monitored by Tycho Brahe, who had managed to observe some quite spectacular comets and supernovae. He finally had to admit that they were further than the Moon, and this challenged the whole of Greek physics.

Robert Hooke in 1664 observed that the comet had internal structure and produced its own light, so could not be reflected sunlight. But why did its tail get so much brighter near the Sun? Was it a braking effect? Was it disintegrating? Could a comet go behind the Sun and come out from the other side? Johannes Hevelius did lots of drawings of comets and the comet of 1682 was observed all across Europe. Edmond Halley worked out an orbit, which indicated it would come back in 1758. So it did, and this famous fellow that bears his name has been back a few times since.

So, when a 14 year old Charles Messier saw a six-tailed comet in 1744 he became hooked. He was already interested in Astronomy and by the age of 21 he was receiving a privileged education as a student of Joseph Delisle, who supplied all things astronomical to the French Navy and the palace of Versailles. He was based at the Hotel de Cluny in Paris and was lucky to be funded by the French aristocracy, who were happy to fund all his comet hunting as well as other astronomical phenomena, such as transits and other experiments to work out the shape of the Earth. (In the UK there was no public money being spent on astronomy at the time, part from a little at Greenwich.)

So, Messier was employed to look for comets, but was finding himself thwarted when he would be observing some nebula over several days and realised it was not a comet. He began making a list of them in order to save wasting time on them, and started his final list with the Crab nebula in Taurus.
The rest is history. Dr Chapman says Halley published a list of six objects in 1716, but I don’t know which ones they were. Messier never observed any comet on its subsequent return.

If you want to read his own descriptions of the objects in his catalogue, including those of his contemporary Pierre Mechain, they are copied from originals and are in the 1978 observer’s handbook called ‘The Messier Album’, by John H. Mallas and Evered Kreimer. There is also a lengthy description of Messier’s doings, including his very unfortunate fall through an icehouse door in November 1781 and fell 25 feet down onto the ice.

Messier was called the comet ferret by King Louis xv. He discovered 13 comets and 8 are co-discoveries.

Clear skies.

Stargazing Oxford

The society will at Oxford Astrophysics department’s Stargazing Oxford event today (28th January) (see Stargazing Oxford 2017 for details). If you’re in the area why not come in and say hello. We’ll be on the 5th floor of the Deny Wilkinson Building, Keble Road, Oxford, OX1 3RH between 2pm and 10pm.

Want to know how to get started in astronomy? Got a telescope but don’t know how to use it? We can help. Want to find out more about the society? Come and say hello. Want a free astrophoto? We have some to give away. And if its clear there will be telescopes to look through after dark.

Clear skies.

December’s talk

December’s talk was ‘Electronic Meteor Observing’, by Richard Fleet, who runs what he calls the Wilcot Station, which is in his garden, near the Salisbury Plain. And no, they are not electronic meteors; they are meteors that are detected electronically via the UK Meteor Observation Network (UKMON), and Richard is a welcome regular whose talks are always very interesting.

His latest talk revealed how easy it is for anyone to set up a really sensitive visual meteor observing station. His Wilcot setup consists of five CCTV cameras which are set up at various locations outside his house and in the garden. If you thought a DSLR camera would be more appropriate, stop. Remember that CCTV cameras are designed with high sensitivity in mind as they need to function in the dark, and they can give high speed video results, albeit with fairly low resolution (they would have a lens around f2, and don’t get the ones that are too wide angle). They can deliver mag 3-4 star brightness, which would take a DSLR camera about four seconds of exposure to record, but you must make sure you choose the ultra sensitive CCTV cameras.

CCTV cameras need a little heating element in the window, and the software he uses for monitoring is called ‘UFO Capture’. (No, just in case you’re asking, although he has caught owls, flies, spiders, moths, bats, etc.) When it’s on, the software dozes and is activated if it detects movement. It records at 25 frames a second so captures far more detail than a DSLR camera ever could. You can set them to ignore slow moving objects, such as the ISS, but you will still catch aircraft, moths and other wildlife, but it’s easy to delete the data.

You can leave it running all night, so can record a meteor shower quite comprehensively, although the composite pictures look a bit scatty because of various sporadic you’ll inevitably pick up and the meteor radiant will move considerably during the night. He recorded a whole night of Geminids, 180 meteors in total, and showed a composite shot of them on as seen from the ground. They seem all in a mess until you realise the radiant had moved right across the sky and background stars showed as very long faint trails.

Other interesting items viewed are cosmic rays, which are detected very briefly, unlike meteors, which will cover several frames. The rays will appear on one frame and sometimes have a little spray. Another rare phenomenon is a sprite, which are lightning flashes between clouds 80km up in space. They may last 1/20th of a second.

His five cameras are set up to cover the southern half of the sky, and his software enables him to calculate tracks and heights of the meteors. You can also calculate their orbits. Most of them burn up about 100km above the Earth and even the brightest fireball would only be the size of a grain of sand.

The UKMON network (20-25 cameras at 8-9 stations) covers the south of the UK but the 100km height of these burnups means he can see objects out over France and Ireland, so his recordings overlap with other stations out there. There are other stations in the North, such as at the University of Lancaster, and one called NEMETODE (NEtwork for MEteor Triangulation and Orbit DEtermination), which publishes its findings in the BAA journal.

He has liaised with a station in Graves, France, where they have a radio transmitter that bounces radio waves off the meteors. This means they can work in daytime and by the time you read this they will hopefully have been able to monitor the Quadrantids.

There are networks like UKMON all over the Earth. There is a large European network, EDMOND (European viDeo MeteOr Network Database. Cringeworthy). Between them, these groups have now identified over 250 meteor showers, 20 of them not known before.

Our own Ken Taylor followed on in the after tea talk by talking about radio meteor observing and said that 8 billion meteors hit the Earth every day, and that Graves uses a VHF radio that is also looking for bits of space junk.

As I write this the UKMON website is being revamped but it should be working by the time you read this. There is also a very good video recording covering most of this if you go onto the SPA website. The Society for Popular Astronomy has a website always worth dipping into.

Clear skies.

November’s talk

Eric Dunford’s ‘Space challenges, disasters and triumphs’, was basically his reasoning for space based research, and all the hazards that faces any craft that is sent into space. And hazards there are a-plenty, so much so that even he says ‘why bother!’

Dr Dunford is a retired mathematician who was director of space science at RAL, but is still very much involved. He spoke to us about infra red astronomy in February.

The list of challenges facing any space mission is extensive. Just to put any satellite into space is upwards of £100 million, so international collaboration is standard.
Then once you have your satellite to build:

  • You have size and weight restrictions
  • It has to cope with temperature variables, especially if it’s rotating
  • Vacuum of space. Gases within the satellite can escape and short-circuit the electrics and we can’t just nip out for a quick repair
  • Cosmic rays – they can harm delicate circuitry. X-rays are vicious. Stuff just disintegrates in sunlight in space
  • Debris, even a fleck of paint, can cause damage in space, and solar panels will wear out and lose power.

Then even before all this it has to survive the trauma of launch. So why is this all worthwhile?

Clear skies

Our atmosphere blocks out most of the radiation, so that only a small part of radiation reaches the surface, so the International Ultraviolet Explorer (IUE) was the first observatory put out into space and lasted for about 19 years. It was launched in 1978 and Dr Dunford was involved in image processing.
The Cluster mission consisted of four satellites showing in 3-d how the Sun affected the Earth’s atmosphere and magnetosphere. These were launched in 2002 and are still going, but two of the original craft perished in 1996 when their Ariane V rocket blew up. Dr Dunford is still involved in their operations.

A report on Mondays observing evening

The observing evening occurred on the 28th November and we had about 9 vehicles arrive and quite a few scopes out so there was plenty for members to see and use. It was nice to have a look through a new Tak 8+inch DK scope with some very impressive views, there was also an 8 inch RC, a Mak 5 inch, a 5 inch newt, a 70 mm refractor and I had my 5 inch refractor There were a couple of new members with their scope and its always interesting to get the scopes set up and aligned properly for “easier” use to find objects.

Despite the cloud free skies, it was not as clear as it might have been, the Milky Way Galaxy was visible but not that clear and transparency not great for deep sky viewing. My bins frosted over fairly early on and by the end of the evening around 23:00 there was a layer of ice deposited on them. I checked the temperature on the way home and it was – 1.8 C so not that cold and I noticed that some had to leave early owing to feeling the cold.

Standing out under the stars needs you to be properly attired.

I did not notice the cold at all but, I had kitted myself out with two pairs of socks and padded boots, two pairs of trousers, long sleeved vest, shirt, jumper, thick coat, scarf, woolly hat and gloves with a petrol heater in my pocket.

Thanks to all those that attended.

Change to the programme

Please note that we have had to make a change to the programme. Our December speaker has had to rearrange and will now be coming in June 2017. Meanwhile, for December’s meeting, Mr. R. Fleet is coming to talk about video meteor observing.

September’s talk

Stephen Tonkin lectures in Astronomy at Brockenhurst College and is a member of Wessex AS.  His talk was on ‘Binocular Astronomy’, and he has written a whole book on the subject.

As someone who has long known that beginners should always invest in a decent pair of binoculars before ever trying to buy a telescope I was still impressed by the nuggets of information in this talk.

Advantages of using binocular as opposed to mono vision:

  • Statistical summation gives binocular vision a 1.4 x advantage over monocular vision.
  • False stereopsis is the depth effect that you can get when looking at a deep sky object, even though it is so far away
  • You have a blind spot in each eye, but when you are looking at something with both eyes, you won’t necessarily end up seeing something with the same part of each eye.

Useful nuggets:

  • Your thumb joint fits nicely against eye socket, which makes it easier to hold binoculars steady
  • With large binoculars hold one side with both hands and rest the other side on your arm.
  • You can wear a cap and hold a finger from each hand over the front of the cap and that can keep binoculars steady.
  • A monopod with a trigger grip head is actually a very good stable base for heavier binoculars. He recommends Manfrotto.
  • Make a long dew cap for mounted binoculars by wrapping black material round the end of them.
  • Get binoculars where each side has independent focussing. That makes it easier to focus on astronomical objects.  Cap each side while you focus with the other.
  • For best quality in smaller binoculars go for roof prisms, which do not bend the light so much and are easier to focus. The limit in aperture is limited by the distance between our eyes, giving about 55mm.  Porro prisms fold the light path and make it possible to have much larger apertures.  Binoculars with Porro prisms will be heavier and cheap ones can lose collimation easily.

He also told us not to be fooled by sellers’ claims of certain standards, because the standards are not regulated, so if you’re told the optics are fully coated this does not tell us how many coatings the optics have.  The best optics have seven coatings on all surfaces.  You may think that all 10×50 binoculars have an objective glass 50mm in diameter but if you hold a piece of graph paper over the end of the binoculars you may be surprised and find the aperture is smaller.  Shine a torch into the binoculars at 6” distance and the light cylinder that comes through the eyepiece will also tell you how big the aperture is.  Another giveaway that any binoculars will be rubbish is if they have an orange bloom.  This is to remove the red end of the spectrum.  As red light scatters more easily and will show up defects in the focussing it is easier to put the bloom on, thereby reducing the amount of red light reaching the eye.

Mr Tonkin has a website = www.binocularsky.com, where he goes into lots of details regarding binocular specifications.