HOME » Recent News
| Latest Society News | |
Fifteen intrepid members and family (9 for the BBQ with the remainder arriving later) braved the weather to meet at Woodrow for the Perseid Barbeque - unfortunately it was a bit wet!! |
|
|
|
|
|
Click on the images to see larger versions |
|
Eighteen WAS members attended August’s practical evening were an informal talk and discussion on meteors, asteroids and comets was given. As a precursor to next weeks Perseid WAS BBQ Chris gave an informative talk on these three topics describing in detail the difference between them, how to observe meteors, where to look for the Perseids, and how to take photographs of them etc. WAS was also able to show those persons present its new purchase of a solar scope and it is hoped that we will be able to loan this out to members on a regular basis for observing. Chris has been able to obtain a tripod through work and this has provided a really steady mount for the scope. Jackie also discussed the need to have a working party in order to cut back the bushes surrounding the observatory and it was great to get such a positive response to this. Sunday the 31st of August is the date that has been set aside (weather permitting) and all members are welcome to help with this task It was nice to see a good turn out for the practical evening and with our new found knowledge we hope that the weather will be kind for us next Tuesday (12th) for the annual WAS BBQ and meteor hunt. Sarah |
|
Wednesday 18th June |
|
Mr. Martin Lunn - M.B.E. (for services to astronomy and education) was the guest speaker at our monthly lecture evening on Wednesday 18 th June in the Sports Hall at Woodrow High House, which was well attended. His lecture titled “Pre-Telescope Astronomy” commenced with the building of Stonehenge three and a half thousand years ago which is thought to have fulfilled both astronomical and religious functions. We were told the reasons why moons were given different names, i.e. Harvest, Hunters, Sturgeon, Lenten and Blue moons. Early civilisations gave us Calendars of the world, which were set by the Sun and Moon and measured the day, month and year, and with the stars and constellations were used by farmers for planting and harvesting crops. We heard how the Babylonians gave us a 24 hour clock with 60 minutes to one hour, and how 12 gods gave 12 months to a year. Their original Calendar was 354 days long. Following that came the Julian Calendar, which was in use until the 20 th Century, and has been superseded by the Gregorian Calendar today. Martin also mentioned various early astronomers such as the Babylonians, Greeks, Egyptians, Arabs, Aborigines and Koreans etc., and their early beliefs and contributions to astronomy. He also talked about the first predicted solar eclipse by Thales a Greek philosopher in 585BC. The intervention of the Church and writings in the monasteries in the middle ages changed peoples’ ideas. The monks wrote their diaries in red ink, hence the expression a “Red Letter Day”. Martin talked about famous astronomers such as Aristotle, Ptolemy, Hipparchus, Copernicus (who confirmed that the sun was the centre of the Solar System), Kepler (famous for his laws of planetary motion), Tycho Brahe (who witnessed Supernova 1572 in that year, and also saw the Great Comet of 1577), and Gallileo who looked at the heavens through a telescope in 1609 and discovered the four Galilean moons of Jupiter. These new ideas about the universe, and the use of the first optical telescopes changed the course of astronomy forever. Martin then went on to talk about Viking Astronomy, which is of particular interest to him, although he said it is a very difficult area to research, and was ongoing. He had given a lecture on the Vikings at the Viking Festival in York, where he is Assistant Curator of Astronomy at the York Museum. Paul Millington thanked Martin for a very enjoyable and informative lecture. A raffle was held, and refreshments were available. Jan Dell |
|
 |
|
Martin gives his talk |
|
See end of this report for links to the Kitt Peak websites |
|
On the 11th June WAS was given the opportunity to hold an extra, unscheduled meeting. Steven Peterson, a Public Outreach specialist from Kit Peak Observatory in Arizona was returning to the UK on business after a forty year absence. He used to live at Naphill and found out about our society from doing a Google search. Steven contacted Jackie Harris, our secretary, and very kindly offered to give WAS members a talk on his work at the Kit Peak observatory. Jackie took him up on this offer and on Wednesday evening about forty members and guests (from other local astronomy societies) attended the meeting. In 1958 the 13 acre site was designated suitable for the observatory and at 7000 feet altitude and a perfect, arid climate it was easy to see why. Kit Peak has the largest collection of telescopes in the world – 23 telescopes on the same site. Steven went through the major telescopes with us, giving details of what each one was used for. The McMath-Pierce 1.5m scope is a solar telescope. The Mayall 4m scope, which was built in 1972, is used for the study of dark matter and this is the most prominent telescope on the site. The newest telescope is the 3.5m WIYN telescope is the most optically refined ‘scope. The Kit Peak observatory has made some important science discoveries including galaxy rotation curves, high redshift galaxies and the distance scales. |
|
Steven then went on to discuss the opportunities that visitors have at Kit Peak. They have nightly stargazing programs, overnight stargazing programs and advanced observing programs. With all of these there is a hands on approach. Guests can have a go at visual observing, CCD imaging, webcam and DSLR imaging. Finally Steven showed us his astro “set up” in his backyard and some of the stunning photographs that he had been able to achieve with his equipment were amazing. A big thank you must go to Steven for contacting WAS and offering to give us a talk on his work. This was an informative and enjoyable extra evening. |
|
The following links take you the various sites devoted to Kitt Peak (all links open in new windows): |
|
In my last report recently I stated that Wycombe Astronomical Society had been treated to two excellent talks, now we can make that three. On Wednesday 16th April Jocelyn Bell Burnell came to WAS and gave a talk titled “In pursuit of Pulsars”. We started off by listening to an audio recording of a Pulsar (a pulsating radio star), which was pulsating at 660revs/minute. This sounded a bit like a rough running car engine. Jocelyn then gave a run down on the birth/ life and death of stars and where pulsars fitted into this system. All stars are born in dark areas of a galaxy. These areas are rich in molecules and dust particles, which become concentrated, and increase in gravity. The increased gravity pulls in more particles, which raise its mass and gravity again, this increase pulls in more particles and so the sequence continues. The temperature of this star gets hotter and hotter and when it reaches 10 million Kelvin nuclear reactions start in its core, and the star begins to shine. This nuclear reaction is called nuclear fusion, during which hydrogen is changed to helium and the extra energy produced by this reaction is light. Our Sun, a “typical” star currently half way through its life cycle, “burns” 600 million tonnes of hydrogen per second. |
|
The stars in the Pleiades (M45), which are 120 million years old, are ten times the mass of our Sun. They will burn their energy much faster and will die “young”. They were likened to a young man in a sports car; bright and flashy but with very little money in the bank! It is these massive stars that will end as pulsars, and will show an orange or red hue. They are past their prime and will use up all of their energy quickly. Firstly they will run out of hydrogen in their cores, then they cool and their exterior swells, the interior shrinks and gets hotter. Because these stars are massive they can repeat this process several times over. Helium will burn to carbon, carbon then burns to nitrogen, nitrogen to oxygen and so on working its way through the heavier elements (silicon, sulpha, nickel and iron). When this reaches the iron stage it stops. It’s the end of the road for the star, as iron will not burn down to the next element. The star explodes, and a supernova has occurred. These supernovae are extremely bright. The central 5% (iron) will shrink and shrink in an attempt to get hotter and try and burn more energy however it is unable to do so. This central core left is the Pulsar. The shredded, exploded elements of the supernovae gradually move away into space. It is the molecules from these elements that become concentrated together and the life cycle of a star starts again. |
|
Jocelyn then discussed some of the properties of Pulsars. They have a mass of 10^27 (ten to the power of 27) and a diameter of 10 miles. They have a big mass and tiny size with an average density that is comparable to that of an atom in a nucleus and a strong gravitational force; it is so strong that it can bend light! Their gravity can affect clocks; they will tick two times slower than on earth. All Pulsars will rotate as a solid body and will spin on their vertical axis. Near the magnetic poles (which isn’t at geographical north) the magnetism leaves the rotating star in a cone shape and somehow the radio waves are funnelled out of this cone. I say somehow because Jocelyn explained that we are now 40 years on from the discovery of pulsars and yet we still do not know how this process really works. The radio waves emitted are very weak. At this point in her talk envelopes were handed out with a small slip of paper in them. This simply read “in picking up this piece of paper you have used a million times more energy than a radio telescope receives from all the known pulsars in a year”. A fact that I find difficult to comprehend! We also had a demonstration of a “pulsar”. Using her kitchen timer tied to a piece of string, Jocelyn spun this around her head. We could all detect the warbling sound of the pulses as it went round and round, and as she spun it faster the pitch of the sound changed. In summary, Jocelyn mentioned the names of modern items that have been called pulsars such as a Nissan car, a geranium flower, and pulsar watches, the latter being an appropriate name, as pulsars are excellent timekeepers. However the watch company had not heard of the historical name, and tried to sue the radio astronomers in the United States! This made us all chuckle. This was an excellent talk and Jocelyn was a very good speaker who is obviously passionate about her subject. Some forty members and guests attended the talk and showed their appreciation at the end with some excellent questions and answers. Sarah |
|
Wycombe Astronomical Society has recently been treated to two excellent talks. (April and March) |
|
April 3rd - Practical Evening |
|
At Aprils practical evening we were given an excellent talk by WAS member Stefan Zietara. It started with a video, set to music by the band “Take That” showing that there are simply hundreds of eyepieces available to choose from. Stefan then went on to talk about the history of early eyepieces with slides showing the different types and designs, and how they had evolved from these early ones into the more advanced varieties available today. He told us that planetary observation and widefield and deep sky observing require different sizes and types of eyepieces, and advised how we can best build up a good collection of eyepieces to suit our observing needs. |
|
 |
There were many different types of eyepieces on display for all to have a look at and discuss, including Stefan’s own “Holy hand grenade” – a huge Nagler eyepiece. At the end of the talk Stefan presented WAS member, Sandy Giles with a book. Sandy won the competition question, posted on the forum, to give a name to his new eyepiece – “Naglarsaurus Rex” or N.Rex for short! Jan Dell won second prize with her name of “Cosmic Canonball”. It was apparent that Stefan had put a huge amount of effort into assembling his talk together as an excellent Powerpoint presentation, and it was appreciated by all the members that attended. Thanks Stefan very much for a most enjoyable and informative evening! |
March 19th |
|
March’s main lecture saw the welcomed return of popular speaker and astrophotographer Nik Syzmanek. We were in the sports hall at Woodrow for this lecture which was just as well as about 60 members and guests attended; an excellent turnout! Nik’s lecture was an updated version of the previous one that he had given to us but it had lost none of its appeal. He showed us many beautiful photographs, which were all taken by a variety of different methods. The emphasis of his talk was very much for us all to try astro-photography and see what results we could achieve. There was some humour added into the lecture as well, like the photographs of the anatomically correct snowmen, taken when a planned visit was hindered by bad weather rendering photography impossible. The lecture finished with an eight minute video, set to the music of Chaldean Crossing by The Enid, showing a variety of astrophotographs and scenery at La Palma in the Canary Islands. |
|
On Saturday 23rd February Woodrow High House and Wycombe Astronomy Society hosted the first beginners “starting out in astronomy” course, organised by the Society of Popular Astronomy.
The event was deemed to be a great success. Over 90 tickets were purchased before the day and several more tickets were sold on the day. It was a jam-packed meeting with several lectures on various topics of astronomy from the different types of telescopes available, finding your way around the night sky to observing the Moon and Sun and more distant objects.
The meeting, held in the sports hall at Woodrow, had an SPA stand where books / CD’s / sweatshirts etc could be purchased, a display for Wycombe Astronomical Society and David Hinds telescopes also had a display of various telescopes / the new Celestron “skyscout” / binoculars etc. They were also on hand to offer advice to potential new ‘scope owners.
During the lunch hour Chris opened up the WAS observatory for all the guests attending the lectures to have a look and this generated much interest in our society.
All in all it was a very successful day for the SPA and for WAS as we were able to welcome some new members to our society. |
Images by Jan Dell |
The Society held their annual Telescope Evening on Wednesday 16th January at Woodrow High House in Amersham. This is an event where members with telescopes and other astronomical equipment can talk about their experiences when using these items and give helpful information to those considering making a purchase. We had planned to hold this event in the Sports Hall, but with the benefit of a clear sky we decided to do some observing. The area around the Observatory was waterlogged from heavy rain, so we set up our telescopes in the Woodrow Car Park. Thirty-eight members and potential members attended, and objects viewed included the Moon, M42, M45, the Auriga clusters and Mars, as well as others of interest. Our Society is thriving and has enrolled a number of new members recently, who have made contact via our website, and come along to our monthly Practical Evenings. Our Telescope Evening is a great way to help people who are new to Astronomy and are keen to learn more about this absorbing and fascinating hobby. An informative and enjoyable evening was had by all who attended. Jan Dell |
|
 |
On Thursday 13th December 2007 Wycombe Astronomical Society held their annual Christmas Party and Quiz at Woodrow High House. Twenty two members attended, and brought along various items of food for the buffet. Sarah Whittaker our Publicity Officer compiled an excellent Quiz consisting of seven picture boards for us to identify the following categories:- Constellations, Famous Astronomers/Scientists, Planetary Satellites, Famous Observatories, Messier Objects (by number and common name), Solar Features/Phenomena, and the hardest category of all on Lunar Features. We were divided into five teams of four people. There was a possible 72 marks on offer. The winning team achieved marks in the 60s’, and each received a prize. Our thanks to Sarah for such an interesting and challenging Quiz and to Committee members for making it such an enjoyable social evening. Jan |
 |
Click on the images to see a larger version |
|
November’s practical astronomy evening was “Coping with dew” and Chris gave a talk to 22 WAS members on this subject. Starting with a definition of what dew is and why it occurs Chris then went on to talk about methods of preventing it. The most effective method is to start by using a dew shield and this can be either a proprietary one, or a home made one made out of a black camping mat and some Velcro to hold it in place. Other methods included the use of dew heaters that keep the tube of the telescope marginally warmer than the ambient temperature and a hair dryer, used to produce a gentle warm breeze onto the corrector plate to reduce dew. Afterwards we were able to get out and do some observing as the weather was clear. The main focus of attention was comet 17/P Holmes, which many members were able to see through the ‘scope for the first time. We were also able to take a look at Mars, although it was still too low on the horizon to get really decent views. The society’s green laser pointer was put to good use pointing out the comet and constellations such as Aquarius, Perseus, the Square of Pegasus, Delphinius etc and objects such as the Andromeda galaxy. It was nice to see so many people at the practical evening and for the societies facilities to be put to good use. Sarah |
|
|
|
|
Click on it to see a larger version. More images in the Image Gallery |
Observing Comet 17P/ Holmes For those of you who have been following the forum recently you will have noticed that it has got quite busy; in particular there is a thread on Comet Holmes. This comet started off as an insignificant “star” (we cannot see a the tail as it is behind the comet - because we are between the comet and the sun), however Holmes decided to explode a few days ago and is now a magnitude –2.5 and a nice object to track down in the evenings. It is easily visible with the naked eye and looks lovely through a pair of binoculars. On Wednesday evening (30 th October) eight WAS members got together at the observatory to take a look at comet Holmes. Binoculars and the societies ‘scope were used and some imaging carried out using a CCD camera was done as well. We will look forward to seeing these in the image gallery. If you want to track down comet Holmes for yourself go to www.spaceweather.com where you will find a link to a map showing its position……its worth a look! Sarah |
|
On Wednesday the 17th of October the WAS annual general meeting was held. Attendance was very good this year with some 40 or so old and new members coming along. The meeting went very well. Paul Millington gave a good account of the previous year and thanked the committee and individual members for their work involved in the running of the society. We also had reports from Chris Rowland and Kelvin Stephens with regards to the observatory and finances. This was followed by an auditors report from Nick Presney. The success of the practical astronomy evenings were discussed and a request was put to the audience for future subjects. The election of officers stands the same with no changes in the current positions. Perhaps the best thing about the evening was that it was nice and clear. So following on from the meeting and a cup of tea and biscuits we were able to do some practical observing. At one point there were, I think, some 16 members crammed around the telescope in the observatory! |
||
|
On Wednesday the 19th of September WAS saw the return of popular speaker Barry Kellet. Originally titled the life and death of stars Barry then changed this to the birth and death of stars and the process from beginning to end was discussed. The first part of the lecture was used to talk about entropy. Barry asked his audience to “bear with him” while he discussed the process and after some explaining it became clearer as to what entropy had to do with star birth. Essentially entropy is a measure of disorder or chaos. Where gravity pulls things in entropy pulls things out. Barry discussed the process of molecular cloud collapse and entropy in this role, protostar formation, proton chain reactions, nutrinos, white dwarf deaths and much more besides. This was the first time Barry had presented this talk, using a presentation borrowed from a colleague. Although challenging to the audience at times, the subject material proved to be very interesting and was delivered by Barry in an informative and interesting presentation. Sarah Whittaker |
||
The Perseid Barbeque 2007 a report by Sarah Whittaker The start of the 2007 observing season got underway on Saturday 11th August with our annual Perseid BBQ. The weather during the day had been wonderful; bright, hot and sunny and it was looking promising for a clear evening. There was a short blip in the afternoon when it came over quite stormy and cloudy – was this because of the threat of some new telescopes coming along? Fortunately it didn’t last for long and we had good clear skies. We also had a good turn out with about 30 members, old and new, coming along – it was nice to see so many there. Edward and Chris went back to their boy scouting days and quickly got a campfire going and the BBQ’s were set up. Woodrow had agreed that we could use their facilities again this year and this was appreciated as we could keep all the telescopes away from fire and BBQ smoke. Chris set up the society ‘scope and proceeded to do some observing and imaging. Others had brought their own ‘scopes along. We had nearly the whole range of Celestron ‘scopes set up including Paul’s new Nexstar 5” and Stefan’s new Celestron CPC9.25”. Other scopes included an 8” and two refractors. Several members brought along binoculars and it was nice to see everybody sharing equipment and looking at the night sky. Although the Perseids were present there were not as many as expected and it seemed that there was a lot of “did you see that one” and nobody else had. David seemed to clock up the most – he must have been in the right place at the right time, all the time. It was nice to see the International Space Station make a fly past a couple of times during the evening and another highlight was an Iridium Flare that occurred. It caught several members by surprise as it started off as a dull satellite moving across the sky and then suddenly became exceptionally bright (down do a magnitude –7,-8) which lasted a while and then faded again. This was the first Iridium flare seen by several members. Many objects were viewed through the telescopes including Alberio – a nice orange and blue double in Cygnus, the Double Cluster which is two open clusters found in Perseus (this was appreciated through Stefan’s “hand grenade” of an eye piece!), the Double Double – two sets of double stars within the same field of view found in Lyra, the Andromeda Galaxy (M31), The great globular cluster M13 in Hercules, the Mini Coat hanger, the Ring nebular (M57), Jupiter and much more besides. Objects viewed through the binoculars included the Coat hanger and Andromeda Galaxy. I think a lot of the newer members appreciated Stefan’s input in pointing out various objects in the night sky and showing us how to locate them, especially the Coat hanger and Andromeda galaxy and so thanks must go to him for this. If you haven’t seen the “Coat Hanger” before it is worth grabbing a pair of binoculars and taking a look: to find it you need to locate Altair, the lowest of the three stars that make up the Summer Triangle. Next sweep up in a straight line from Altair to Vega, the right hand star of the summer triangle. The Coat Hanger is found about a third of the way up and slightly to the right; you can’t miss it. Its pattern is that of an upside down coat hanger or elongated J.
The evening started to wind up about 12.00am with a few hardened soles staying on till 1am and beyond. It was agreed by all that it was a lovely evening and lots of observing had been done. It is hoped that we will be able to organise another “star party” BBQ for later on in the year and that this will be just as successful. Some further images: -
|
||
From low Earth......... Designs of craft were presented to the audience and considerations were made for power and propulsion, protection from radiation, thermal control, protection from dust particles and communication. One of the ways Davids’ craft was to be powered was by Antimatter: sub atomic particles (atoms, electrons and neutrons) which, when they come into with other atomic material, annihilate it, producing pure energy as a result. This was an interesting concept. Already small quantities of antimatter energy are being produced at the CERN organisation for nuclear research. 1mm diameter of anti hydrogen is equivalent to 2 tons of TNT.….think what one could achieve with larger quantities! Davids talk to us on a journey, first to Mars and back – travelling at under the speed of light – then onto an outer planet and finally onto a class A star. All of these journeys could be achieved within the crews life time! This was an excellent talk by David and it was very evident that a lot of time, effort and research had gone into it. |
||
Visit to Greenwich - click here to see a report by Sarah Whittaker on the visit to the Greenwich Observatory. |
||
|
Click on image above to see larger version |
||
 Image by Jan Dell - |
||
On Saturday 3rd March approximately 30 members and friends gathered at Woodrow to observe the Total Lunar Eclipse. This Star Party had been planned for the recent occultation of the Pleiades by the Moon, but unfortunately the weather was not on our side for that occasion and it had to be cancelled. However for this eclipse the weather was kind to us for once, and the sky was beautifully clear. Woodrow House had kindly agreed that we could use their new BBQ area and a BBQ was set up, serving hot jacket potatoes, which everyone enjoyed. |
||
At the other end of the field many members set up their telescopes (approx 10 in total), binoculars and cameras on tripods. The society’s observatory was also opened up and this gave the opportunity for some of the newer members and friends to observe Saturn for the first time whilst waiting for totality. The eclipse started at approximately 20.20 pm and it wasn’t long before a ‘bite’ taken out of the moon, in the bottom left corner could be seen. By 11pm totality had been reached and the moon turned a beautiful coppery red colour. At this point cameras were clicking rapidly as many photographs were being taken! At around 11.30pm most members were beginning to get cold and the group began to disperse. Thanks must be given to Alistair who helped many members with their photography techniques, whilst trying to take his own photos, and to Chris who was wandering around with a hair dryer on a 100 ft extension cable. He was carefully drying everybody’s optics, as scopes, cameras and binoculars had started to dew up. Thanks also go to Jan and Sarah for providing the jacket potatoes. It was agreed that an excellent evening was had by all. |
||
Members from Wycombe Astronomical Society and five visitors met in the Sports Hall at Woodrow High House on Wednesday 17 th January for the annual Telescope Evening, at which members set up their various pieces of astronomical equipment in the form of telescopes and tripods, cameras, webcams, and binoculars for discussion with other members. A variety of telescopes were on display, ranging from 80mm to 11” including reflectors, refractors and Schmidt Cassegrains, showing both equatorial and alt. azimuth mounts. Of particular interest was a home made wooden equatorial wedge that one of our members made on which to mount his Celestron 11” telescope. This was set up with a webcam, and a deep sky imager which he had constructed from a “job lot” of pieces that he had bought. The whole set-up was very impressive, and apparently worked very well. |
Click on either image to see a larger version |
|
Tea and coffee was available, and a raffle was held. The evening finished at about 10pm. No observing was possible that evening due to a cloudy sky. |
||
 |
||
|---|---|---|
|
Useful links: Ed Wright’s home page
|
|
Saturday 16th december |
Geminid Meteors
Unfortunately, being a Saturday many members had other arrangements, but ten members met at the Observatory at 8pm, and enjoyed hot homemade soup and French bread, whilst waiting for the Meteors to show. When they did appear, the number of meteors observed was disappointing with only about half a dozen, spread over an hour or so. During the evening, the Observatory 10” Meade Schmidt Cassegrain scope was set up, and several members bought their own scopes and binoculars. One member bought his parallelogram and mounted his large binoculars on it for us all to try out. It gave an excellent and impressive result. Objects observed during the evening were the Moon, Saturn, M45 The Pleiades, and Messier objects in Andromeda, among others. The sky was very clear, and the air cold, and ideal for observing. We finished observing at around midnight, and a good social evening was had by all those attending |
|
Society visit to Herstmonceux |
  |
|
This article first appeared in the December 2006 issue of the BBC Sky @ Night magazine. |
||
|
Observations of Delta Cephei Chris Rowland, Jan Dell, Sarah Whittaker, John Fifield Members of the Wycombe Astronomical Society made observations of the magnitude of the star Delta Cephei to determine its period and so its distance using the period-luminosity law for Cepheid variables. Data Collection Delta Cephei is a naked eye star in the Constellation Cephus. Its magnitude varies regularly over a period of a few days and there are two convenient comparison stars nearby. WAS members made a total of 116 observations from June 2005 to February 2006, giving magnitudes from 3.4 to 4.3. We made measurements using naked eye or binoculars. When measurements were made independently by several observers at the same time the magnitude estimates were within 0.1m or 0.2m of each other. The poor weather and light pollution made Delta Cephei difficult to see sometimes and on some occasions the fainter comparison star was not visible. This will make the fainter observations less reliable. The raw measurements are shown here; there is no obvious pattern to the data. See fig 1 The data was analysed using the Anova method and a plot of the period shows a clear peak with a period of 5.3691 days - see fig 2 A plot of the data at this period gives a clear indication of the light curve - see fig 3 This shows the characteristic Cepheid "shark's fin" light curve with a rapid rise followed by a slow decline. This is the official light curve - see fig 4
|
|
Determining the distance to Delta Cephei The absolute magnitude of a Cepheid variable is given by the function For our measurement of the period this gives an absolute magnitude of -3.41; in other words if Delta Cephei was at a distance of 10 Parsecs (32.6 light years) it would have a magnitude of -3.41 and so be the brightest object in the night sky, except the Moon and sometimes Venus. The formula: The average magnitude from our measurements was 3.92. This gives a distance to Delta Cephei of 294 Parsecs, or 958 Light years. Comparison with Official values The period of Delta Cephei is 5.366 days; our measurement is within 50 seconds of this. The average magnitude is actually 4.07m, our measurement is slightly higher, possibly because of a tendency to overestimate the brightness when the star is only just visible. The distance to Delta Cephei has been measured by the Hubble space telescope using parallax as 891 light years. Our measurement is within 10% of that, almost entirely because our mean magnitude is less than the actual value. This was an interesting and educational exercise, and we learned a lot about taking and recording observations. Chris Rowland |
||
| More society news..... | ||
Content © 2007 Wycombe Astronomical Society. No part of this site may be reproduced in any way without prior written permission. Read our Privacy policy.
Wycombe Astronomical Society is a UK Registered Charity No. 297024. Connectivity supplied by Internet Services.