A Very Happy New Year

with lots of

 Clear Skies in 2010!

 

 

MEETINGS

 

 

COMMITTEE MEETING

 

        Members of the Committee are respectfully reminded that there will be a meeting of the Committee on Tuesday January 12th 2010 starting at 1930 at Phil’s house.

        Any member of the Society is also very welcome to attend but please let Phil Berry know before hand.

 

 

DECEMBER MEETING

 

        Phil Berry opened the meeting by giving a brief account of the Autumn Moon Watch that took place on Friday 27th of November as reported in the December issue of the Society Newsletter.  He said that the event had been a great success and had been visited by a number of local people as well as members of the Society.

        One piece of interesting feedback was that students from Uplands College who attended with their tutor, Iain Pert had subsequently asked if they could use Phil’s observatory to support their course work.  I think we are all pleased with the interest generated.

        Phil then introduced tonight’s speaker, Paul Treadaway. 

        In recognition of Galileo’s first use of the telescope 400 years ago, 2009 was declared The International Year of Astronomy, and reports of many events to celebrate this can be found at:www.astronomy2009.org

        This is an account of how Paul has been contributing to the commemoration.

 

Building the T200

A Talk by Paul Treadaway

 

        In 1609 Galileo made his first reported observations of the night sky, looking at the Moon and its craters and then at Venus to discover that the planet exhibited phases as observed from the Earth.  Paul began by showing a slide of an exact replica of Galileo’s original telescope with Florence in the background.

        Having described the history of the telescope and Galileo’s announcements followed by his condemnation by the church, Paul described clearly how the optics of a telescope work, and included many of the problems encountered with different lenses and mirrors such as chromatic aberration found in simple lenses to spherical aberration problems in mirrors, both spherical and hyperbolic and how they are reduced or overcome.

        Then he moved onto his own personal contribution to 400 years of the telescope, involving him in making his own telescope from scratch.

        First of all, Paul went through all the choices he had before him; whether to make a refracting or reflecting telescope and what size it should be.

        Since he was grinding his own main optics, his choice was to make a mirror since that would be an easier challenge both to grind, polish and then to figure.

        Next Paul needed to decide whether he should make a spherical or hyperbolic mirror.  The choice for a hyperbolic curve was made because of the problem of coping with spherical aberration.

        He went through the maths for focal length and magnification and concluded that the most practical size for the mirror would be a diameter of 200 mm; hence the name “T200”.

        The focal ratio directly dictated the length of the telescope and with a focal ratio of f7 and 200 mm aperture, the focal length would be a manageable 1.4 metres.

        A very stable platform was going to be needed to work on the mirror and it was decided to use a 55 gallon oil drum.  This gave the necessary stability and as the grinding process was going to use a lot of water, a series of drain holes were drilled all round the edge of the top of the drum.

        Securely attached to the top of the drum, were the three mounting blocks that were to secure the wooden platform which was going to hold the Pyrex blank.

        For the grinding process, it was necessary to have a Pyrex blank and a regular glass blank to act as the “tool”.  These Paul obtained from a firm in Essex and costing £120 for the pair.

        One final thing needed before he began was a template that would act as a guide during the grinding process.  Paul measured this using a screw sunk in his driveway as the focal point, then measuring 1.4 metres away, carefully drew the curve on a sheet of metal that was then carefully cut to that shape.  He now had his guide-template.

        Having secured the Pyrex blank to the wooden platform on top of the oil drum and using number 80 grade carborundum powder and water, Paul began the slow process of grinding the blank with the tool.  He moved the “tool” gently back and forth over the blank; walking round the drum as he went.

        Every so often he would wash off the black and draw a grid on the blank with a graphite pencil.  When he returned to the grinding process, he could then see how evenly he was working by looking at how the lines were ground away and then he could make adjustments; then after more grinding, check again.

        Using the template Paul was now able to see how closely he was to the required shape as he progressed.

        It had been reputed to take about 3 to 6 hours to complete the Rough Grind.  Paul said it took him nearer 24 hours to complete.

        This concluded the first stage of grinding the mirror blank and we look forward to his next informative talk when Paul will describe further processes in preparing the mirror.

 

        Following Paul’s talk, mince pies and coffee were enjoyed over a chat.  After this there was a short talk on basic focusing methods used in astronomical telescopes.  A brief summary follows under “Other News and Information”.

        The meeting was concluded by another talk by Brian Mills, our “Sky Notes compiler”.  Brian’s talk was in two parts.  The first part was reminding members of the Ursid Meteor shower which took place from about 17th December with a maximum on Christmas Day and Boxing Day.  The radiant point would have been in Ursa Minor.  Although a weak, narrow stream it felt worth mentioning.  The other meteor shower Brian talked about was the Quantrantids which he refers to in the Sky Notes for January.

        The second half of Brian’s talk was a fascinating, well researched talk about the Star of Bethlehem.  He has written a short version of this talk which appears under “Other News and Information”.

 

 

JANUARY MEETING

 

        Wednesday 20th January 2010 – Jan Drodz is a member of the Society and has spoken to us about the Environment and how the World’s survival as we know, it relies on our care.  This time he returns to talk about “Jan and His Instruments”.

        This is also the Society’s Annual General Meeting and all are welcome.

        Meetings begin at 1930 although members are invited to arrive anytime after 1900 as this is a good time to exchange ideas and discuss problems and relax before the talk.

        The venue as always is in the Upper Room of the Methodist Church at the east end of Wadhurst Lower High Street, opposite the entrance to Uplands College.  (For those with SatNav – the post code is TN5  6AT)

 

 

FUTURE MEETINGS

 

        Tuesday 12th January 2010 – There will be a meeting of the Committee from 1930 at Phil’s as mentioned earlier in the Newsletter.

 

        Wednesday 17th February 2009 – Details of the meeting to follow.

 

 

OTHER NEWS AND INFORMATION

       

 

SUBSCRIPTIONS 2010

 

        Come January, we enter a new session of the Society, and again, the subscriptions remain the same as in recent years.  Membership for the year is still £15.00 and £20 for two members within the same family.  Children and students are free and always welcome.

 

 

BASIC TELESCOPE FOCUSING

 

        Before you get anywhere with your telescope, you need to be able to focus it.  The first time a telescope is used it will be unfamiliar so we need to set the focus as near as we can before seriously seeking sharp images.

        It may be that the telescope is so far out of focus that nothing can be seen and racking the focus control shows no visible difference.  Under these circumstances it is necessary to find a bright object in daylight.  Removing the eyepiece and looking into the focus tube it should be possible to locate the light.  Set the telescope’s focus to about the centre of its travel and replace the eyepiece but don’t tighten it in the collar.  Move the eyepiece in and out so that some kind of focus is achieved and lock off the eyepiece.

        It should now be possible to use the telescope’s main focus control to bring the image to a sharp focus.

        Most telescopes use a rack and pinion system where the control rotates a worm drive in a grooved rack.  This is fairly successful for most observations on less expensive telescopes.

        Unfortunately for more exacting and sustained focus, a certain amount of backlash caused by a slight gap in the worm mechanism may exist.

        A more precise focus controller called the Crayford focus control uses roller bearings which provide a much smoother and more continuous adjustment.  They are more expensive; a good one can cost from £50.

        Just because good focus has been achieved with the telescope, it is always a good idea to re-check it again after the telescope has been panned across the sky in case of any imbalanced internal strain.

        To achieve an even more precise mechanical focus it can help to replace the focuser with a micro-focuser.  This uses two focus controls.  One outer control focuses the telescope at the normal rate and then an inner control focuses at 1/10th the speed allowing much more accurate sensitivity.  Sadly these are much more expensive starting at somewhere about £100 but can be well worth while.

        Now we come to electronic auto-focusers.  An electronic image such as that from a CCD camera is scanned electronically and maximum contrast output is searched for via a motorized servo control.  The motor moves the focus control either side of maximum and settles at the centre point; the focus point.  In this way focus is established maintained continuously.  It is necessary to be close to focus first of all.  Auto focusers cost from about £50.

Text Box:          Finally, there are several masks that aid focus.  One is credited to a Russianamateur astro-photographer, Pavel Bahtinov.  The mask fits in front of the telescope.  It basically consists of three sets of parallel straight slits set at an angle to each other:

        The template for various sizes can be downloaded from: http://focus-mask.com/Free_Templates.html

        When observing a star through the mask, the observer sees the star with “spikes” spreading out from it on either side.  As the focus is adjusted, the central spike moves either side of the star.  Exact focus is achieved when this central spike is exactly in line with the star.

 

Geoff Rathbone

 

 

 

WAS THERE A STAR OF BETHLEHEM?

 

        The story of the nativity appears in the Gospel according to St. Luke, but contains very few of the elements that we have come to associate with the birth of Christ. For instance there is no star, no mention of Herod or the Magi and no slaughter of young boys, all of which appear in the St. Matthew version. Luke refers only to the Shepherds, the baby in swaddling clothes and the manger. The Protoevangelium of James (one of hundreds of books used by the early church) does talk of a star but is thought by scholars to be simply a retelling with embellishments of Matthew’s story which he wrote around AD150.

Text Box: The Bahtinov Mask        The order of events in the gospel according to St. Matthew (King James version) is in brief:-

§          The star reveals the birth to the Magi.

§          The Magi travel to Jerusalem and ask where the “King of the Jews” has been born because they have seen the star.

§          Herod hears of their arrival and gathers his priests and asks where a messiah would be born.

§          They reply “Bethlehem” because of a prophecy that said a messiah would be born there.

§          Herod speaks privately to the Magi asking when the star appeared and for them to let him know when they find the child.

§          The Magi leave and “Lo the star which they saw in the east went before them till it came and stood over where the young child was”.

§          Magi present 3 gifts and leave but return to “their own country” by a different route after a warning in a dream.

        It’s worth remembering that there are many translations of the gospels all of which vary in their descriptions. For example in the New Revised Standard Version “Star in the East” becomes “Star at its rising” and “Wise Men” become “Magi” in the New International Version.

        One of the important questions that need to be answered is when Jesus was born. Estimates range between 12BC and 9AD with there being general agreement on a date somewhere between 7 and 5 BC. The date of Matthew’s gospel is known to be between AD80 and AD100 so it is extremely unlikely that he wrote it from his own experience but it is thought probable that it is a second hand account from a variety of authors. There is a general consensus of opinion that Herod died in 4 BC because of coins found that have that date with details of his successor on them. Also we are led to believe that Joseph and Mary had gone to Bethlehem (Joseph’s ancestral home) to take part in a census, but there is none recorded until AD6-7.

        The choices for what could have been the “star” are:-

·          A Miracle. If this was the case then it is impossible to analyse it scientifically. Some modern theologians say that they can fully accept the fact that there was no star without it harming their Christian beliefs in any way.

 

·          A Planetary Conjunction. There are a few such events that fall within the required timeframe.

o         Conjunctions of Jupiter and Saturn in 7 BC which Kepler himself calculated, although for some reason he thought that a planetary conjunction would cause a nova.

o         A series of conjunctions between Jupiter and Regulus in 3-2 BC. These were significant because Jupiter was referred to as the “King” planet whilst Regulus was the “King” star.

o         A conjunction of Venus and Jupiter in 2BC.

 

Brian Mills

 

SKY NOTES FOR DECEMBER

 

Planets

 

Mercury passes through inferior conjunction on January 4th after which it becomes a morning object. It may just be visible in the dawn skies although it will always be quite close to the south eastern horizon (within 6 or 7 degrees around the 19th/20th/21st) rising a little over an hour before the Sun.

 

Venus is not suitable for observation this month due to its superior conjunction on the 11th.

 

Mars on the Leo/Cancer borders is now visible all evening, rising at 17.30 by mid month. It’s position is shown for the middle of the month, reaching its closest to Earth on the 27th when it’s magnitude will be -1.3.

 

 

 

 

Jupiter at magnitude -2.1 on the Capricorn/Aquarius borders is very much an early evening object as it sets by 17.15 mid month.

 

Saturn in the constellation of Virgo at magnitude +0.8 rises by 23.00 around the middle of the month. See the map above for its position. The ring system is gradually opening up as viewed from Earth following our crossing of the ring plane.

 

Note: The Earth is at its closest to the Sun (perihelion) on January 3rd whilst the full Moon is at its closest to Earth (perigee) on January 30th.

 

 

Lunar Occultations

As usual in the table I’ve only included events for stars down to around magnitude 7.0 that occur before midnight. DD = disappearance at the dark limb and RD = reappearance at the dark limb.

If anyone would like more information about these occultations or times for fainter events then please let me know.

Times are all GMT.

 

 

Jan.

Time

Star

Mag.

Ph

PA °

20th

22.17

SAO 128487

6.9

DD

47

25th

17.04

GSC0181401648

5.7

DD

98

25th

17.04

SAO 76425

5.5

DD

98

27th

17.11

SAO 78079

5.8

DD

119

28th

16.58

SAO 79216

7.0

DD

122

28th

18.44

SAO 79294

3.5

DD

88

28th

21.57

SAO 79386

6.5

DD

107

28th

22.26

SAO 79403

5.3

DD

112

 

 

 

 

Phases of the Moon

 

Full

Last ¼

New

First ¼

30th

7th

15th

23rd

 

 

 

 

ISS

Details of all passes can be found at www.heavens-above.com

 

Jan.

Mag

Time

Alt°

Az.

9th

-2.1

18.29

36

SSW

11th

-2.8

17.36

46

SSE

12th

-3.5

17.57

80

SSE

13th

-2.5

16.43

43

SSE

13th

-3.5

18.18

78

NNW

14th

-3.3

17.04

76

SSE

14th

-2.1

18.38

41

WNW

15th

-3.4

17.25

80

N

16th

-3.5

17.45

77

N

17th

-3.5

18.06

84

S

18th

-3.4

16.51

76

N

18th

-2.8

18.26

50

SSW

19th

-3.4

17.12

87

SSW

20th

-2.7

17.32

54

SSW

 

Iridium Flares

The flares that I’ve listed are magnitude -3 or brighter. There are many more flares that are fainter, occur at lower altitudes or after midnight. If you wish to see a complete list, go to www.heavens-above.com   Times are all GMT.  Remember that when one of these events is due it is often possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time.

 

Jan.

Time

Mag

Alt°

Az.

1st

18.19

-3

46

NE

2nd

18.13

-4

47

NE

5th

17.58

-4

52

NE

9th

17.39

-3

60

NE

10th

17.33

-8

61

NE

12th

17.23

-5

64

NE

18th

18.49

-8

40

NNE

20th

16.41

-5

73

ENE

25th

18.15

-8

53

NNE

 

Meteors - The Quadrantids

 

The Quadrantid meteor shower is active from January 1st through until the 6th with the maximum occurring on the evening of the 3rd at 19.00 hrs. Hourly rates of around 80 are expected but moonlight and the low altitude of the radiant in the early evening will reduce this considerably. At the 2008 maximum, rates of around 160 were recorded although this was for a short period of just a few hours. The radiant lies close to Ursa Major and is associated with what is now the defunct constellation of Quadrans Muralis (the Mural Quadrant) that dates from 1795. That area of the sky now lies in the constellation of Boötes (the Herdsman).

 

Brian Mills

 

 

 

NASA’S SPACE PLACE

 

Sunglasses for a Solar Observatory

By Patrick Barry

 

        In December 2006, an enormous solar flare erupted on the Sun’s surface. The blast hurled a billion-ton cloud of gas (a coronal mass ejection, or CME) toward Earth and sparked days of intense geomagnetic activity with Northern Lights appearing across much of the United States.

        While sky watchers enjoyed the show from Earth's surface, something ironic was happening in Earth orbit.

        At the onset of the storm, the solar flare unleashed an intense pulse of X-rays. The flash blinded the Solar X-Ray Imager (SXI) on NOAA's GOES-13 satellite, damaging several rows of pixels. SXI was designed to monitor solar flares, but it must also be able to protect itself in extreme cases.

        That’s why NASA engineers gave the newest Geostationary Operational Environmental Satellite a new set of sophisticated “sunglasses.” The new GOES-14 launched June 27 and reached geosynchronous orbit July 8.

        Its “sunglasses” are a new flight-software package that will enable the SXI sensor to observe even intense solar flares safely. Radiation from these largest flares can endanger military and civilian communications satellites, threaten astronauts in orbit, and even knock out cities’ power grids. SXI serves as an early warning system for these flares and helps scientists better understand what causes them.

        “We wanted to protect the sensor from overexposure, but we didn’t want to shield it so much that it couldn’t gather data when a flare is occurring,” says Cynthia Tanner, SXI instrument systems manager for the GOES-NOP series at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. (GOES-14 was called GOES-O before achieving orbit).

        Shielding the sensor from X-rays also reduces the amount of data it can gather about the flare. It’s like stargazing with dark sunglasses on. So NASA engineers must strike a balance between protecting the sensor and gathering useful data.

        When a dangerous flare occurs, the new SXI sensor can protect itself with five levels of gradually “darker” sunglasses. Each level is a combination of filters and exposure times carefully calibrated to control the sensor’s exposure to harmful high-energy X-rays.

        As the blast of X-rays from a major solar flare swells, GOES-14 can step up the protection for SXI through these five levels. The damaged sensor on GOES-13 had only two levels of protection—low and high. Rather than gradually increasing the amount of protection, the older sensor would remain at the low level of protection, switching to the high level only when the X-ray dose was very high.

        “You can collect more science while you’re going up through the levels of protection,” Tanner says. “We’ve really fine-tuned it.”

        Forecasters anticipate a new solar maximum in 2012-2013, with plenty of sunspots and even more solar flares. “GOES-14 is ready,” says Tanner.

        For a great kid-level explanation of solar “indigestion” and space weather, check out :

spaceplace.nasa.gov/en/kids/goes/spaceweather.

 

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

 

 

Caption:

X-9 class solar flare December 6, 2006, as seen by GOES-13’s Solar X-ray Imager. It was one of the strongest flares in the past 30 years.

 

 

CONTACTS

 

Chairman     John Vale-Taylor

                                                      pjvalet1@btinternet.com

 

Treasurer            Mike Wyles                          01892 542863

                                                      mike31@madasafish.com

 

Editor            Geoff Rathbone                         01959 524727

                                                      geoff@rathbone007.fsnet.co.uk

 

Events                  Phil Berry                             01892 783544

                                                      phil.berry@tiscali.co.uk

 

Director of Observations       Brian Mills    01732 832691

                                                      Brian@wkrcc.co.uk

 

Wadhurst Astronomical Society website:

                                                      www.wadhurst.info/was/

 

SAGAS web-site                        www.sagasonline.org.uk

 

Any material for inclusion in the February 2010 Newsletter should be with the Editor by January 28th 2010