Issue No. 1, July 1995

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LATEST NEWS

EAAE Provisional Executive Committee's first meeting at ESO Headquarters

- The EAAE constitutions and by-laws as they were first proposed by mail to the EC members and then modified according to their comments, by the secretary, Roland Szostak, were thoroughly discussed and adopted; they will be submitted for the approval of EAAE members at the Athens Conference. It was also decided that the EAAE headquarters will be located in Garching.

- The treasurer, James More, reported that he was not able to open an account until the association is officially created; consequently, he has temporarily put on its own account the fees collected from the 86 members who were registered during the Workshop. It was discussed how new EAAE members could pay their fees to the treasurer in the cheapest way, owing to the taxes which have to be paid for money transfer: there is generally a minimum tax charge, which, for example in the UK happens to be greater than the provisional fee which was adopted during the Workshop. It was decided that each of the National Representatives, who, according to the proposed constitution are intended more generally to work as accommodation addresses and assist the council in its work concerning their country, will act as sub-treasurers: they will have to open an account for collecting the fees in their country.

- The president reported on the progress of the organisation of the November Conference. A proposal has been submitted to the European Commission in the frame of the 1995 European Week for Scientific and Technological Culture; it has not yet been accepted: in particular, more emphasis has to be put on technology. There seems however to exist some reasons to be optimistic;.

As it was submitted, actually, the proposal is made not only by the EAAE but also by the European Planetarium Association (EPA). The president reported indeed that, in July 1994, about 40 participants at the International Planetarium Society Conference in Cocoa Beach (Florida, USA), representing Planetaria from 12 European Countries declared their express interest in forming a "European Planetarium Association" (EPA). In the discussion it appeared that there are obvious reasons for the two associations, EAAE and EPA to meet and work in close contact; some of us, however, expressed their preference for having separate constituting meeting. The president stated that joining the two under the title of "European Astronomy Integration" appeared to give more weight to the proposal.

- Michael Reichen reported on the progress of the edition of this Newsletter; he acknowledged receiving many interesting papers.

- Claus Madsen and Richard West presented the ESO project "Europe towards the stars", an Europe-wide contest, which will also take place during the 1995 European Week for Scientific and Technological Culture. Contest subjects are :

* At the telescope - Catching and interpreting the signals;
* Technology for Science - Building an instrument;
* A future Space Mission - Designing an on-board instrument;
* Theory - Looking in the future.

There will be a winning team (up to 3 pupils and 1 teacher) in each country, selected by a National Jury, which, in most countries, associate EAAE members. The winning teams will be invited to visit ESO Headquarters in Garching for a period of one week, during which they will be able to observe via ESO satellite link with two ESO large telescopes.

- At the end, all the EC members expressed their warm thanks to ESO and Richard West who made this meeting possible and welcome us in the same efficient, generous and friendly way that all the participants to the November workshop where so happy to experience.

Lucienne Gouguenheim


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HST Educational Projects (HSTX)

"Dear Colleague,

Thank you for the interest you have expressed in the prototype educational project using HST data (HSTX). Following the large response to the article in ST-ECF Newsletter No. 22, we are in the process of setting up a scheme for data handling, project writing and testing etc., both here in the ST-ECF and amongst the teaching community.

The prototype was produced by purely in-house effort, but the manpower does not exist to cover all aspects of the production of further projects. What the ST-ECF IS offering is as follows: (a) Selection and preparation of datasets from HST archive. (b) Some ideas for projects using such data. (c) Distribution of datasets and ideas to the teaching community. (d) Assimilation and distribution of ideas presented by the teaching community. (e) Preparation in a standard format of project designs received from teachers. (f) Distribution of draft projects for initial testing. (g) Editing of drafts using feedback obtained from testing phase. (h) Distribution of final version. Depending on the nature of the project this could be purely in paper form or could include digital material.

What we are looking to the TEACHING COMMUNITY for is:

i) Ideas for projects.
ii) People who would be willing to write up their ideas (project for students accompanied by appropriate teachers notes) using the datasets from the HST archive.
iii) Teachers who would then try out the project with their students and report feedback.

An e-mail account has been set up for the HSTX projects (hstx@eso.org) which will normally be read once a week. Please send any comments or queries to this account. Before we can proceed much further, we need to know who would be willing to take on some or any part(s) of the process (see (i)-(iii) above). "

Best regards, Patricia Fosbury

HST Educational Projects (HSTX)
Space Telescope - European Coordinating Facility
Karl-Schwarzschild-Str. 2
D-85748 Garching bei München
Fax: +49 89 320 06 480
Internet: hstx@eso.org

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HOU, Hands-on Universe

[...]Many teachers talk about being "re-born" through collaborations with us. We can guarantee many students not only loving astronomy, but also learning information technology, math and science skills of the 21st century. The appeal of astronomy is one that most humans feel.[...] With HOU, astronomy and the Universe can be made accessible to the most disenchanted, most dis-empowered student or teacher [...].

Carl Pennypacker

Note from the editor: Jan Engstedt and other teachers from Sweden seem to be already well involved with HOU, and will hopefully write something for us about their experiences in our next Newsletter.


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ABOUT NETWORKING

I am presently preparing and testing the EAAE 's own homepage on WWW (the World Wide Web), and all the articles you can find in this Newsletter (plus other things!) will soon be available on the Internet. There will certainly be more information on the Internet in the next issue of the EAAE Newsletter. One very useful thing to do for all the future potential users of "the net" would be to write up a list of all the Internet providers known in Europe. To achieve this, we need the help of everybody, because although it is rather easy to get these addresses in one's own country, it is almost impossible to get any information on other countries. So please, try to gather these addresses and send them to me as soon as possible!

Thank you! Michael Reichen


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The Importance of the Internet to the EAAE

During that conference the Compuserve network and the Internet were discussed, Compuserve as being more user-friendly and therefore advisable, Internet as more complex but more important in the world of astronomy. My opinion is that if we have to make a choice, it should be the Internet on account of its state-of-the art developments.

The main problem is the accessibility for individual people on the Internet in the countries with participants in the EAAE. I can only speak for my own country and accessibility in the Netherlands is very good.

The Internet
First of all you should know what the Internet is about. It is the largest computer network in the world. It is a collection of computers, cables and people connected together. It has been in existence since 1985. Technically speaking, the computers are connected by using the TCP/IP protocol. In this way any type of computer can get in touch with any other computer. And because people use these computers, these people can get in touch with each other very easily. In doing so you get a community which could be described as a 'global village'.

There is no 'Big Boss' and therefore it is free of charge. You only have to pay for the connection with the big computer, which is connected to the Internet. This is called a provider. That could be a computer at a university but it also could be a computer at a commercial company. Since universities are everywhere, every country has its own provider. Hence there are lots of students on the Internet, most of them men. We, as teachers, can go on the Internet by using the commercial providers as well. In the last year that development has become more significant. In the Netherlands you can find more than twenty commercial providers, which offer a connection for about 15 ECU a month, with full access to the Internet.

Access
All you need is a computer that is fast enough (386SX or faster, or a Macintosh), and a modem (a 14k4 fax modem is advisable). The software is very easily to get and not expensive. Most of it is freeware or shareware. You can download it, using modem software, or you can get it by paying for the floppy disks and their postage. I must admit that the installation of modem and software can be a disaster for a non-experienced user, but I think it is worth the effort. And besides, a good commercial provider gives good support.

If you have access with SLIP or PPP on the Internet, you really should. With SLIP or PPP you become a part of the Internet with the great advantage of having all its tools at your disposal. SLIP and PPP are protocols that can be used between the computer of the provider and your own computer.

Tools
Once you are on the net you can use several tools. A tool is a piece of software that helps you:

--to find specific information; or
--to connect you with other hosts (= computers) and users (= people).

It is like surfing: you can very easily go in any direction you want. Within two seconds you go from Germany to Chile and from Egypt to Canada. That is what is called 'surfing the Internet'.

Within 10 seconds you can get a file (= program or text) on your own hard disk; no matter where it comes from - Norway or Japan - the method is the same. You only have to read and understand a little bit of English.

When you talk with other persons, be friendly to them! Emoticons such as :-) and :-( are part of the world of 'Cyberspace'. I'll briefly explain the tools.

- Electronic mail (E-mail)
E-mail is the most important tool on the Internet. Everybody on the Internet has an address. My address, vlastuin@bart.nl, consists of my name, the @-symbol (which stands for 'at'), the name of my provider (= bART) and the country symbol. For example, Richard West has for an address rwest@eso.org (Richard West at ESO, organisation), and our editor is known as Back to the Table of Contents

WHO, WHAT, WHERE ?

Nowadays it is a science taught to fourteen years old students in our schools integrated in Physics and Chemistry curricula at the third level of compulsory education (8th grade). Nevertheless, at a secondary education level - fifteen to eighteen year old students - Astronomy is practically non existent.

The Portuguese Reform wish is now taking place at this level doesn't allow its introduction as a new subject without a previous curricula evaluation. Our curricula are still being experimented.

At Portuguese secondary school - 475 - there are two kinds of courses. Some are more University directed than others. Both have a general, a specific and technical formation. The courses which aim to prepare students to enter University have a technical formation with 6 hours per week, and the students may choose one or two subjects out of a list from the Ministry of Education.

But schools may design their technical curricula, with goals, aims and the organisational concepts.

If it isn't possible today have Astronomy as an autonomous subject in secondary school, the Portuguese delegation at Garching, since November, has made several contacts with the Ministry of Education, Astrophysical Department of the University of Porto, and Physics, Geography, Geology and Mathematics teachers.

At this moment this team is discussing several points. The first is to design the Astronomy syllabus to be taught at own schools in 1996-1997. The other is to study the possibility to establish the EAAE in Portugal. Finally, this team wishes to promote activities concerning Astronomy in Portuguese schools.

After all, this science isn't a very developed subject in our country, as you can see by this news. But amongst students specially during their free time at school, it has a great impact. We are aware that there are lots of things to be done for Astronomy teaching in Portugal. But the first steps have been given.

Felisbela Martins teaches in Escuola Secundaria S.Mamede de Infesta, Rua das Laranjairas, P- 4464 S.Mamede Infesta, and Eugénia Ribeiro teaches in Escola Secundaria Fontes Pereira de Melo, Rua O 1 de Janeiro, P- 4100 Porto.

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Blossoms of Science: A Centre for Science Education in Israel

The staff of Blossom of Science at the Jordan Valley Regional College includes researchers, teachers, youth guides, and teams working on courseware for science education. Among the services offered by Blossom of Science are an astronomical observatory, operating a 14 inches telescope with electronic camera, an information centre, and some 15 different extracurricular astronomy classes.

Various educational projects in Astronomy have been developed for kindergarten, elementary and high school students. In addition, a project now under development will help to make satellite photos available to high school students .

To know more, about Blossom of Science, please, contact : David Pundak
Jordan Valley Regional College
Jordan Valley 15132, ISRAEL
fax : 972-6- 773757
e-mail : dudu@yarden.yarden.ac.il

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Understanding the Earth's place in the universe.

A teacher education pack on astronomy

The PSTS project has carried out research into primary teachers' understanding in a number of areas of science, including basic astronomy, and then written teacher education materials based on the results of the research.

The astronomy research investigated teachers' understanding in a number of key areas including:- observations of the sky; explanations for day and night, the seasons and phases of the Moon; and the structure and scale of the universe. Significant problem areas were identified together with a general lack of confidence among many of the teachers. However, what also emerged from the research, was a genuine interest in astronomy and a strong desire to learn more.

The teacher education pack addresses the problem areas highlighted by the research. It starts with the knowledge and ideas teachers already have and aims to give teachers scientific knowledge and understanding which makes sense to them and which they can use with confidence.

The pack itself is written as a course to be worked through, preferably, though not exclusively, with a group of teachers. It is in four main parts and takes the form of a journey. The journey starts from the Earth, with feet firmly on the ground, and gradually moves out to encompass the Moon, Sun, planets, solar system, galaxy, and universe. The introductory material and Part 1 consider the sky and what can be seen in it. The apparent movements of the Sun and the Moon are dealt with in some detail. The research showed that few teachers had a sound observational base for their knowledge. The Moon in particular caused problems. Other research indicates that primary teachers are unlikely to be alone in this!

Part 2 takes the reader away from the surface of the Earth to consider the Earth and the Sun as separate celestial bodies and to explain the phenomena of day and night. The journey continues in Part 3 to explain the seasons and the phases of the Moon. Part 4 moves on to encompass first the solar system, and the distinction between planets and stars (another area of difficulty identified in the research), and then our galaxy and its place in the universe.

Throughout the pack the emphasis is on 'active' learning. Each new section is introduced with a series of discussion activities to elicit the ideas, understanding and confusions which the participating teachers already have. The scientific ideas are then presented, supported by numerous practical activities. The activities range from structured discussions to modelling with globes, ]lights and balls of various kinds, to model making with umbrellas, stickers, wires and card. Full instructions and any necessary templates for the models are included in the pack. Specialised equipment is not used. Everything needed can be found in the average primary classroom.

One of the key aims of the pack is to enable readers to develop a sound understanding of the structure of the universe - again, this was an area of difficulty identified by the research. In order to facilitate this, scale models are introduced and reinforced throughout the pack. A swimming pool model for the Earth - Sun system has been found to be particularly helpful and is used extensively. As part of the appreciation of scale, attention is drawn to the need to approach many standard drawings and diagrams found in books with a 'scale warning' in mind.

Although the pack is initially aimed at helping primary school teachers develop their scientific understanding, it can also be used successfully in a number of different contexts. It has been used with other groups of adult learners, and would be helpful for many secondary school teachers. One suspects there may be many secondary school teachers, without a background in astronomy, who have similar difficulties to those identified in primary teachers. Also many primary teachers have adapted the activities for use directly in the classroom. Similarly, as the approach of the pack is to emphasise discussion and practical activities, much of it is very suitable for use with pupils in a secondary classroom.

The pack is available from:
The ASE (Association for Science Education)
College Lane , Hatfield
Herts. AL10 9AA
England. (Tel. 0707 267411)
(Cost [[sterling]] 8.50 + p&p.)

Jenny Mant works for the Primary School Teachers and Science Project (PSTS), Oxford University Department of Educational Studies and Westminster College, Oxford, UK. References and additional information on the PSTS may be obtained from her or from Mike Summers, Dept. of Educational Studies, Oxford University, 15 Norham Gardens, Oxford OX2 6PY, UK

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,H2>EDUCATIONAL EXPERIENCES

European Students together in school: A cultural exchange experience between Spain and Italy.

This encounter allowed teachers and students from the "Paolo Baffi Institute" in Fregene and "Txorierri Institute" in Derio (Bizkaia, Spain) to compare and discuss their own educational experiences. The coordinators of this cultural exchange were the authors of this short report, who, in the past months had work "at distance" in order to "focus" the main objectives of the exchange, which were:

a) Updating and integration of themes in Astronomy (Gnomon) for the students studying this discipline in their scholar curriculum, and for the ones who showed particular interest for the "problematic of Astronomy"

b) Improvement of the study and use of a foreign language.

The two-day program was the following.
- first day: a guided and commented tour of the some of the monumental solar clocks in Roma was organised. Nicoletta Lanciano, from the "La Sapienza" University in Roma, author of an "inventory" of the roman solar clocks in 1993, acted as a consultant.

- second day: the original project of constructing a solar clock, studied by J. Sarasola and E. Esteban (see fig. 1 and 2) was presented at the seat of the "Paolo Baffi Institute". Such a solar clock is already in operation in the "Txorierri Institute". The project was commented by J. Sarasola and his students who, later on and together with the italian students, realised the "hard paper" model of this solar clock in order to demonstrate practically its functioning.

We have noted that this cultural exchange experience has allowed the achievement of a very important objective: the "activation" of a cooperation between European young people which proved useful both on the cultural and human levels.

This way, the bases for further contacts are already set, contacts during which the scientific themes will be later on amplified. Already now it is obvious that the sensibility of these young people is a very good potential in order to face the urgent problems like the control and limitation (fight!) as much as possible of light pollution which does not allow a correct view of the night sky.

We hope that our experience will serve as an example and stimulus also for colleagues.

Julen Sarasola, teacher in the Batxilergoko "Txorierri" Instituta, 48016 Derio (Bizkaia, Spain), end Giuliano Casali, teacher in the "Paolo Baffi" Instituto Technico. Viale di Porto 205, I- 00050 Fregene - Roma

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About measuring time

Knowledge aims:
a) To recall to our students' attention that to localise an event means always to put it in a right place and in a right time.

b) To underline how difficult it is to define the essence of time.

c) To make the students understand that the choice of a sample unity of time is an arbitrary act.

d) To know the most important steps in the evolving of calendars in the Mediterranean area.

Practical goals:
a) To find midday by the use of "gnomon".
b) To compare the scanning of time in astronomical phenomenons, and the measurement of time with a clessidra and with other modern instruments made by man.
c) To make tables to compare "hora aequalis" and "hora inequalis" meaning hours passing with the rhythm of day and night or with other physical phenomenons we can assume as periodical. Furthermore to build a handmade tool for the regulation of different hour counting systems.
d) To evaluate in local time events as reported in different hour frames by ancient literary, musical and historical texts.

As regards the b) and d) of the knowledge aims it is necessary to cooperate with literature, history and philosophy teachers. When we have the opportunity to enlarge this report, we shall be clearer on working details.

Operational steps
Introduction: "The Chronotope".
To discuss in class how the fourth dimension in the time and space universe is a novelty only in the scientific field, whereas it was a natural feeling at the beginning of the human attempts to organise Knowledge. The suffix -topo of the word "crono topo" means "place" from ancient Greek, but in Italian it also means "mouse" ! This is why we use this picture shown here to pick up the attention of our students on this philosophically very important point.

- The first experiments we do in class are to measure time in a biological sense: the student must realise that he has, without a watch, a different feeling of time according to the different objects of his interest. We can also make him realise that time evaluation is different at different ages.

- We also measure the length of a table with a rigid ruler and with an elastic: why is it not the same ?

- The problem is not to define what TIME is but to measure its intervals. This measure needs a periodical phenomenon to refer to. The choice of such a phenomenon is somewhat arbitrary in as much as it depends on what particular phenomenon we decide to consider. The oldest choices are linked to the alternating of day and night. We build a rudimentary sundial and we take systematic measurements with a gnomon

- In co-operation with the teachers of Literature and History we make some excursus on calendars and on famous examples of data and time referring like Dante Alighieri's "Divina Commedia" and "Convivio" or operas like "I Pagliacci" of Leoncavallo, or historical documents.

- In co-operation with the teacher of Science we examine the kinematics of solar system in connection with the movements of Earth, and the problem of geographical and heavenly co-ordinates, may be in a summary way.

- The last step we do is to build a diagram of the yearly course of the time equation and to produce a gadget to translate seasonally the "Italian hours" into local time.

(Note: we remind that up to I750 instead of national times nearly all European Countries were using so called "'Italian hours" which started at the "AVE MARIA" prayer, at the end of twilight).

The above topic, which we suggest to discuss all the year long with our students, leaves an open question if we, teachers, want to go deeper in a methodological sense. Astronomical watches are explained by means of gravitation forces but also clessidras and pendulum clocks movements are explained by the same kind of forces. Only atomic watches movement is scanned by a different kind of phenomenon. Which one we must choose to synchronise the other ?

Lidia Nuvoli & Cristina Palici di Suni belong to the Working group of Physics training and didactic and History of Physics seminaries, General Physics Institute, Torino University, Italy.

Project Work: "Astronomy at ... "

Since 1987 I have been teaching at Padrao da Légua Secondary School, in Matosinhos, Portugal. This school year (1994/95) I am teaching two classes of the 11th form (15-17 years old youngsters).

Four students, who also sign this project, have been taking part with me in the monthly seminaries called "Astronomy at 21h", open to the public and held by the Oporto University Astrophysics Centre since the 1 4th of April 1994.

On the 12th of September 1994 the Pedagogical Board of Directors of our school approved a project called C.R.E.S.C.E.R. (meaning: growing up), to which I belong and through which we hope to promote the idea of a school as an educational and cultural space, increasing success at school. Its main goals are:

- Carry out activities which contribute to the students' development of their initiative, organisation and autonomy spirit.

- Improve the creative, formative and productive use of their free time.

Thus, related to this Project we present the following activities that we have been carry out in the last months.

2. Project Work:

Goals: - Increase the youngster's interest in a branch of Applied Maths which will be a formative occupation of their free-time.

- Develop the elders' interest in team work and scientific

- Not forget the importance of a healthy relationship that human beings should develop among one another.

A. "Astronomy at ... " (Public Sessions)

Themes: - "A night of observation with a little telescope"

- "Galaxies"
- "How is a star born?"
- "The portable planetarium" (in collaboration with the Oporto University Astrophysics Centre and the Matosinhos Town Hall).

B. "Star-Newspaper" ("Astrojornal")

Contents: - Writing about the sessions mentioned above.
- News about the recent events on Astronomy.
- Presentation of project works made by the target-audience.

The students responsible for the A and B activities were all from the 11th grade of A and D classes: Luisa Alexandra Tavares, Marina Isabel Gomes, Monica Andreia Silva and Pedro Rodrigues, while the responsible teacher was Prof. Maria Jos Galhano.

The "target audience" was classes A and C from the 7th grade (12-13 years old students).

3. The first three sessions

In the three sessions presented by the 11th form students, the subject was treated in a simple way and according to the knowledge of the target-audience - 7th A and 7th C students.

At the end of each session, working proposals, which were done with engagement and enthusiasm, were delivered. As a result and due to such participation, we decided to give only a "special" prize and a simpler present to the rest of the participants. In these works, all the data requested, such as pictures, photocopies and even photos, is presented.

Each of these sessions was filmed for the School File so that it could be used in the future.

As an example we show at the end of this short report one of the proposals presented on the day of our 2nd session.

4. The planetarium
The fourth session had the collaboration of two monitors and their "portable planetarium" from the Oporto University Astrophysics Centre and it was filled with a lesson about Star and Planetary Astronomy. It had the presence of the target-audience, as well as the presence of teachers and other students who had shown interest in watching the session.

5. A night of observation
This project will be considered finished when, by the month of May a "Night of Observation " in Dr. Manuel de Barros Astronomical Observatory will take place, with the presence of the 25 students who have followed us along these sessions.

Eugénia Ribeiro teaches in Escola Secundaria Fontes Pereira de Melo, Rua O 1 de Janeiro, P- 4100 Porto.

Note from the editor: examples of proposals presented to the pupils and photos of work done by the target audience could not be included here for technical reasons, but are available by the author.

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OBSERVATIONS

The device consists in a plane projection of a limited portion of the celestial sphere. It is essentially composed of two parts, cut out of one of the flaps of a DIN A4-size cardboard folder (see fig.1): a narrow 14 by 6 cm equatorial strip (part A) and a piece of cardboard with one flap folded over that represents the morning (evening) sky background (part B). The equatorial strip can pivot around an axis that coincides with either the East cardinal point (sunrise) or the West cardinal points (sunset). Assembling is extremely easy: one has just to punch a hole at the spots marked by an asterisk on parts A and B, then assemble both with any kind of fastener and fold the flap over along axis XY.

Graduating the device is very straightforward: 1 cm represents 10deg. degrees. This gross oversimplification is however justified in so far as we are merely concerned by the apparent path of the Sun just after sunrise or just before sunset. It goes without saying that before building the device, one has to decide whether he intends to study sunrise or sunset and adjust graduations accordingly.

On the equatorial strip, the crosswise graduation represents the Sun's declination at equinoxes and solstices while the intermediate graduations correspond to the Sun's declination at mid-seasons (i.e. about May 6 or August 8 and Nov. 8 or February 5, when the Sun's declination is d= + 16deg.). The lengthwise graduation represents the time of sunrise (sunset). An alternative would be a graduation in time to elapse before (or time elapsed after) meridian crossing (hour angle). The Sun's apparent path on a given day is always parallel to the celestial equator: this should be presented as a rule of the game to the children using the device.

The horizon line on part B shows the cardinal points. It can also be graduated in azimuths although younger children may not be conversant with the use of a compass. After building the device, one should make sure that the horizontal graduation are still visible as part of them may be hidden by the adjustable strip. Operating the device is easy: one has just to tilt the strip from vertical with an angle corresponding to the local latitude. With younger children, an approximate setting will suffice. It could for instance be derived from previous guided observations of the Sun's apparent path.

Basically, the device can be used in two different ways: either to account for an observation or to predict what is going to happen. For instance, after observing a sunrise/sunset (i.e. its time and azimuth), the pupil can transfer his observation onto the device, thus visualising the apparent path of the Sun. More experimented pupils could also estimate the Sun's declination from the device and by comparing with a sky chart, find which constellation it is in.

The device can also be used as an analogue calculator to predict the points of sunrise/sunset on any given day at any given latitude, provided that it should not be too close to the pole. To that purpose, find the apparent path corresponding to the selected date, adjust the equatorial belt according to the latitude and read off the corresponding azimuth on the horizon graduation. Testing what happens at different latitudes simply requires setting the equatorial belt at the adequate angle.

In fact, when teaching the annual wandering, the stumbling block is the daily change of the Sun's declination. The approach usually adopted in class does not work too well mainly because most of the times we try to account for the phenomenon by resorting to concepts that are hardly mastered or even come into conflict with the misconceptions that are usually present in children's minds. Using the device, the pupil is given a chance to build up gradually relationships between what he can understand (dates, cardinal points) and what he has difficulties in grasping (the declination of the Sun, its hour angle, its annual motion along the ecliptic).

Once he has realised that, although the points of sunrise/sunset do change with the date, it is in fact the same Sun that rises and sets, things should be easier. He has thus been prepared to understand that the annual wandering of the points of sunrise and sunset depends on two factors: the seasonal variation of the Sun's distance to the celestial equator and the local latitude. Moreover, using the device gives pupils an opportunity for genuine scientific practice. As they change the parameters (date and latitude) according to fancy in a first step and more rationally later, they are progressively induced into such practice (i.e. identifying the variables that account for a phenomenon, modifying them, using logic, predicting,...).

Jacques Vialle is a member of the CLEA, (Comité de Liaison Enseignants Astronomes), 26 Parc Bérengère, 92210 Saint-Cloud (France)

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Seeing is Believing !

This article shows how your students, by means of simple observational methods, may measure the distance to our sister planet Venus. In addition, if they compare observations from different months, your students may easily show that Copernicus was right.

What is Venus ?
Venus is a well known planet, similar to our Earth. It's slightly closer to the Sun then we are. Around the turn of the century, the Swedish researcher Arrhenius even believed this planet could support life. Simple calculations showed that a planet like our own would only have a slightly higher temperature, around 35 C, if placed that close to the Sun. Arrhenius imagined the planet atmosphere having a composition similar to our planet during the Carbon period, where primitive life flourished all over. However, in the 1970's, Russian spaceprobes showed that our sister planet has extreme, killing temperatures, 500 C above what was expected. These high temperatures are the result of a powerful greenhouse effect. Venus has a thick cloud cover with an atmosphere more than 100 times as massive as ours. This thick atmosphere acts as a huge quilt, reflecting practically all infrared heat back to the surface of Venus. Looking at Venus with an ordinary astronomical telescope, you will observe how the surface is totally covered by these thick clouds.

However, one interesting detail will appear. You may see there is both a sunlit part and a shadow part. Astronomers say, this planet shows "phases". The same word is often applied in relation to our moon. If the moon is full, the phase is 100%, if the moon is half, it's phase is 50%. Similar to the moon, the phases of Venus change all the time, depending on where the planet is placed. These phases have played a most important role in astronomy history.

Is the Sun, or the Earth placed in the centre ?
The Greek astronomer, Ptolemeus, introduced a solar system in the year 140. Ptolemeus believed the Earth, not the Sun had to be placed at the solar system centre. The Catholic Church supported this idea. The Earth with all its wonders was created by God , and thus should be placed in the centre. In 1543 however, the Polish monk Nicholas Copernicus published a book, suggesting the Catholic church was wrong. Not the Earth, but the Sun had to be placed in the centre. The Catholic Church reacted furiously and placed the book at the Index Romanum, the list of forbidden books. Here the work of Copernicus stayed until 1835...

Which world system was the correct one, first had to be proven. One of the very first proofs came due to the Italian scientist Galileo Galilee. He had constructed a telescope and was the first person to point such an instrument to the night sky. An early, cold December morning in 1610, Galileo had observed the phases of Venus, and the first real proof that Copernicus was right appeared.

The Catholic Church reacted again, taking Galileo to court. Galilee's support for the Copernicus' theory had nearly implied his sentence to death by fire. A similar faith had previously been provided to another Copernicus supporter, Bruno Giordani.

However, today, astronomy is peaceful, without such risks. If you want to repeat Galilee's observations and proof, here is how to do the experiment. Try this yourself:

- Find a good telescope, an astronomical telescope with 25-50 x enlargement is beautiful. When Earth is close to Venus, an ordinary home-binocular will be sufficient.

- Ask your students to bring a piece of paper and a pencil. Before the observations start, they have to draw a nice circle on their paper.

- Now, let your students observe the phases of Venus. One from each group has to make a detailed drawing. Tell them they have to watch the planet at least for half a minute, in order to enjoy the short moments of calm, steady air.

- Then, let them draw the phases. Let the groups compare their results, in order to see who is most accurate.

How can these phases show anything about the solar system ?

Now comes the trick. The Earth, the Sun and our sister planet Venus together join in a gigantic triangle. We call the corresponding angles for Earth, Sun and Venus: "E", "S", and "V".

The angle E is very easy to estimate. The method below is not 100% accurate, but there is no need to introduce high math on simple measurements. We all know our planet Earth performs one rotation (360 degrees) in 24 hours. This corresponds to 15 degrees pr hour. Let your students check this themselves.

The first photo above was taken on December 14, 1994. That day, planetary almanacs, programs etc. told us that Venus was straight south at 9.23. During the next 3 hours our Earth rotated so much, that it now was the Sun, which at 12.15 was placed in south. During these 2 hours and 52 minutes (= 2.866 hours), our planet Earth had rotated from Venus to the Sun.

The corresponding angle E thus has to be 2.866 hours x 15 degrees pr hour = 43 degrees.

(If you have a measuring device like the sextant, this angle E may be measured directly, but do not forget the solar filter.)

Now we have gotten very close to the solution. Go into your laboratory, and place a torch light , slide projector, or similar powerful light source on the floor. We will now try to make a scaled down version of our solar system:

- Take a piece of chalk, and draw a line, 149,6 cm long, going from the light source to where you stand (Planet Earth is placed 149,6 million km from our Sun).

- You now only have to draw the angle E, in our case above: 43 degrees.

- Extend the right leg of this 43 deg angle, so it runs out in the laboratory for say 2 meters.

- Find a circular object (Galileo took an apple, but an orange is even better). Place it along this angle-leg. Let the light from the our light source fall on the orange. Please observe how the phases vary according to increasing distance.

- Vary the distance, until the phases correspond to our December photo. Now you have a correct model of the solar system. Your students may directly measure the Earth-Venus distance, and the Sun-Venus distance.

- Calculate the angle E for our other observations, January 17 1995. On that date, the Sun was placed in south at 12.31; Venus passed south at 9.15. Show the angle E is equal to about 50 deg.

- Repeat the drawings for this new triangle.

- Again, move the orange until its shadows are comparable with our Jan CCD photo. Now measure the Sun-Venus distance, and the Earth-Venus distance. Please observe; the Earth-Venus distance has increased dramatically, but the Sun-Venus distance has remained constant.

If Venus keeps a constant distance to the sun, it has to perform a circular orbit. This means, Copernicus, Bruno Giordani, and Galileo were all correct: The Catholic Church was wrong.

As you may see, these observational arguments are simple, and they convinced Galileo that Copernicus was right. Even though Galileo was forced to deny all his results, his daring work opened the Age of Enlightenment, and actually changed the world.

Additional work : CCD cameras may be applied too. Measurements on our CCD photo from Jan. 17 1995, show that Venus had an angular size of 23 arc seconds. 3600 arc seconds correspond to one degree. Your students may estimate the planets physical diameter from this information.

Compare it to our Earth's diameter, and the diameter of Mars. Why is Venus often called a "sister-planet"?

Note to the teacher.

Kepler's 3. law may be applied too, allowing the students to calculate the orbital period T. The energy needed if we could move Venus out to further distances may be calculated, and compared with the total nuclear arsenal.

The method above might be refined in several ways. A lot of more mathematics might be introduced, including sine relation, great-circle distances, etc...

However, these simple hands on arguments and student performed drawings/discussions actually give equally as good results as many much more complicated derivations.

Suggested readings , J. M. Rogers, "Physics for the Inquiring Mind", p. 248, Princeton 1960.

Have a nice Hunt ! M. W.

Mogens Winther teaches in the Amtgymnasiet, Grundtvigsalle 86, 6400 Sonderborg (Denmark).


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How hot is the sun ?
Measuring the solar constant

A simple planet-climate model will be constructed, applications will be demonstrated for the planets Venus, Earth and Mars. In addition, global effects of enhanced CO2 pollution and solar variability will be illustrated.

DEFINITION:

The solar constant ( as defined for planet Earth ) is the power collected at the top of the atmosphere by a unit area perpendicular to the light path. In what follows, the unit area will be 1 m².

PRINCIPLE OF THE MEASUREMENT

The energy collected by a brass (or aluminium) cylinder will be determined by calorimetry. From this measurement, a value of the energy collected at ground level per unit area will be derived.

Next, a value of the solar constant may be derived either from the combination of several measurements, or from a table that summarises the influence of refraction, absorption and scattering (see Complements for the teacher in next issue of the Newsletter! ).

The value of the solar constant thus derived will lead to an estimate of the total power radiated by the Sun, and, using Stefan's law, to an estimate of the temperature of the Sun's photosphere. The brass, or aluminium, cylinder should absorb as much of the total radiation as possible in the visible and IR domains and should trap the extreme IR radiation remitted by the heated cylinder.

REQUIRED MATERIAL

* a 5-cm diameter, 1,5 to 2-cm thick brass (or aluminium) cylinder with a hole drilled along one of its diameter
* a 5-cm diameter PVC sleeve (the kind used in construction for down pipes)
* a U-shaped clamp collar
* a short length of PVC piping, the kind used by electricians
* a thermometer
* a protractor with a bob line.

Assembling the device (see figure 1 for a 3-D view, and figure 2 for a side section of the sleeve.):

1. set the metal cylinder inside the sleeve and drill a hole through both sleeve and cylinder. The diameter of the hole should be the same as that of the thermometer;

2. weigh the cylinder and paint it mat black
3. glue the cylinder inside the PVC sleeve making sure the holes are correctly aligned;
4. fill the bottom of the sleeve with a polystyrene foam block;
5. glue the sighting tube on the slide of the device, 90 deg. from the thermometer hole, and the protractor with its bob-line (that will be used for the measurement of the Sun's zenith distance, i. e. the angle between the local vertical and the direction of the Sun);
6. place the completed device onto the U-shaped clamp collar.

STUDENTS ACTIVITIES

1. Measuring the power collected at ground level
Procedure
- With the help of the sighting tube fitted with a screen, adjust the device so that the angle of incidence of light should be normal to the flat base of the cylinder.

- It is a good idea to cool the cylinder in a refrigerator, half an hour before start will do.

- While adjusting the device, make sure the cylinder does not receive any light from the Sun. To that purpose, mask it with a polystyrene lid.

- Measure the outdoor air temperature [[theta]]1.

- Then remove the polystyrene mask and expose the cylinder Now read the cylinder temperature during every minute.

- Plot your numbers on a graph like below. Our cylinder will receive heat from the surroundings, if its is cooler than air temperature.

- If our cylinder is hotter than [[theta]]1, it will loose energy. Best conditions, no interferences from outside, are found around [[theta]]1.

- Draw this tangent and find its slope [[Delta]][[theta]]/[[Delta]]t.

- Finally, make a measurement of the Sun's zenith distance z. During the whole experiment, make sure that the cylinder remains perpendicular to the direction of the Sun (if z changes during the individual measurements, take an average value)

Recording the measurements
* Cylinder diameter 2R =
* Cylinder mass m =
* Initial temperature [[theta]]1=
* Current temperature [[theta]] = ..., ..., ...
* Zenith distance z =

Calculating the power collected by the device
Knowing the specific heat of brass or of aluminium (C=0.38 x10³ Jkg^-1K^-1 and C=0.92 x10³ Jkg^-1K^-1), the area of the cylinder exposed to the sun s=[[pi]]R², and the slope from our data plot [[Delta]][[theta]]/[[Delta]]t, we may now calculate the power collected per unit area (i. e. flux density E) :
E = f(mC,s) f([[Delta]][[theta]],[[Delta]]t)

2. Deriving the solar constant

The power per unit area E found before is influenced by absorption and scattering in the Earth atmosphere. We want to extrapolate this value E to an exoatmospheric value, our Solar constant, Es.

This drawing shows how the atmospheric path of our sunlight is depending on the zenith distance z :

Astronomers often speak about "airmass". If the Sun is placed at zenith, the airmass is 1.
Trigonometry shows that in our general case the solar light has to pass an airmass of 1/cos(z).

The power arriving at ground level declines similar to radioactive gamma ray absorption. There is thus a simple exponential declining relation between airmass and power received.

If you have measured the arrived power per unit area E at different airmasses, the result will be as in the next figure. The trick is extrapolating our measurements backward, the exoatmospheric Es may thus be found as the y-axis interception.

If you have only one measurement, the table below gives the ratio of Es/E, the exoatmospheric solar constant over the power collected at ground level, for different values of the zenith distance and different sky conditions :

Zenith         70d  60d  50d  40d  30d  25d  
distance z     eg.  eg.  eg.  eg.  eg.  eg.  
Clear blue     2.5  2.0  1.7  1.5  1.3  1.3  
sky            0    0    0    0    5    0    
Average sky    4.2  3.5  2.6  2.1  1.8  1.6  
Slightly       5.3  4.3  3.2  2.5  2.2  2.0  
veiled                                       

The accuracy of the result can be challenged because of heat losses in the device and also because a small fraction of the solar radiation is reflected skyward in the upper layers of the atmosphere.

3. Temperature of the photosphere
(The light we receive from the Sun, in the visible domain, comes from a very thin superficial layer, the photosphere, on which we can observe sunspots, for example )

Determining the total power radiated by a unit area of the photosphere
Power Es is collected on a unit area which is situated at a distance dES = 150 x10⁶ km. P, the whole power radiated by the Sun is received on a sphere of area 4[[pi]]dES², hence P = 4[[pi]]dES² x Es.

M, the total power emitted per unit area of the Sun's photosphere (exitance, formerly emittance) defined as M=P/4[[pi]]RS² (where RS = 7 x10⁸ km is the radius of the Sun's photosphere) will be given by:

M = f(dES²,RS²) x Es

Determining the temperature of the Sun's photosphere
Temperature T of the Sun's photosphere is given by Stefan's law: M = [[sigma]]T⁴ with [[sigma]] = 5.67x10^-8 Wm^-2K^-4, hence:

T = r(4,f(M,[[sigma]])) .

4. Origin of the Sun's energy

Several hypotheses can be made as to the origin of the Sun's energy. It may derive from :

* exothermic chemical reactions
* the cooling of the Sun
* gravitational contraction ( i. e. mechanical energy )
* thermonuclear reactions

Three hypotheses may be studied in the last-but-one year of the course of French Secondary Schools. Considerations about the life expectancy of the Sun will lead the students to retain the most probable hypothesis, i. e. that the energy of the Sun proceeds from thermonuclear reactions. The Sun radiates a total power P. Let [[tau]] be the life expectancy of the Sun. Then P x [[tau]] will be the total energy produced by the Sun during its whole life.

4.1. Energy generated by chemical reactions
Supposing that enough molecular oxygen is available to burn all the molecular hydrogen present in the Sun, the energy emitted by this reaction would be mS x PC, where mS is the mass of the Sun and PC the heating power of the Sun's material. Considering all the gases present in the Sun, the one with the highest heating power is molecular hydrogen with PC =124700 kJ kg^-1. Even if PC = 200000 kJ kg^-1, the Sun's life expectancy would be deduced from P x t = mS x PC , hence :

[[tau]] = f(mS x PC,P) with P = 4 x10²⁶ W, giving

[[tau]] = f(2 x10³⁰ x 2 x10⁸,4 x10²⁶) s, or [[tau]] = 30 000 years (10¹² s).

4.2 The cooling of the Sun
If the energy was produced by a cooling of the Sun with mass mS , then the energy dissipated by cooling from temperature T (in Kelvin) to temperature 0 K would be mS C T, with C the specific heat of the Sun's material..

The specific heat of molecular hydrogen (i.e. the gas with the highest specific heat) is 14.4 x 10³ J kg-1K^-1. Because specific heat increases with temperature, one may assume C = 20 x the above value, and thus, from P x [[tau]] = mS C T,

one obtains: [[tau]] = f(mS C T,P).
Taking mS = 2 x10³⁰ kg and T = 6000 K for the photosphere gives [[tau]] = 6 x10¹¹ s, or about 20'000 years.
A 20 000 or 30 000 years solar life is of course too short, compared to the old fossils Darwin had found in the 1830s. There were theories that the Sun may regain part of its lost energy by massive bombardments of meteorites. But then, of course, the Earth should be smashed frequently too, more frequently than observed.

4.3 Gravitational contraction
Gravitational contraction was the main theory in the very first start of our century. The German scientist Helmholz had calculated that the sun may exist for million of years, if it regained its energy due to contraction. This was quite a clever suggestion : such processes do occur some places in space. Gravitational contraction is believed to be the main power source of Quasars. In our own solar system, the gas-planet Jupiter emits huge quantities of infra-red light due to contraction too.

Due to the huge size of the Sun, this would even be a slow process. Helmholz calculated that it would take 7 000 years to obtain a solar size reduction large enough to be visible by Earth telescopes. So, according to this theory, the Sun might be a few million years up to 100 million years old.

However, the big shock came in 1904. Rutherford had measured the a decay of some 238-Uranium mineral. These a decays had imploded Helium into the mineral; measuring the Helium content, Rutherford found that this Earth rock mineral should be billions of years old. The solar system turned out to be much older than any solar theory could accept...

4.4.Energy generated by thermonuclear reactions
The last hypothesis to be discussed is that thermonuclear reactions are the source of the Sun's energy, an idea that was first proposed by Jean Perrin in 1918. A fraction [[Delta]]m of the mass of the Sun is transformed into energy. The amount of energy produced is given by the relation : E = [[Delta]]mc², where c is the speed of light.

For such reactions to occur, temperatures of several million Kelvin's are required. Only a very small fraction of the Sun's mass ( about 10 % ) is concerned. Moreover, not all the mass can be transformed as part of it is converted into helium. The output of such reactions is about 0.7 %.

The total energy generated thus will be : [[Delta]]mc² = mc x 0.007 x 0.1 x c², hence from P x [[tau]] = [[Delta]]mc² we derive:

[[tau]] = f(mc x 7x10^-4 x c²,P ), giving

[[tau]] = 3.15 x10¹⁷ s, or about 10¹⁰ years.

It follows that only nuclear reactions taking place inside the Sun can account for the duration of the life of Sun.

Josée Sert is a member of the CLEA (Comité de Liaison Enseignants Astronomes), 26 Parc Bérengère, 92210 Saint-Cloud (France), while Mogens Winther teaches in the Amtgymnasiet, Grundtvigsalle 86, 6400 Sonderborg (Denmark).

Note from the editor: this article will be continued in the next issue of the Newsletter, with a number of complements for the teacher and suggested exercises related to the topic.

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OPINIONS

LIGHT POLLUTION is one example of the impact of urbanisation on our environment. For several decades now, the night sky has been in retreat before a tide of wasted artificial light, allowed to go upwards by poorly shielded, over-bright and misdirected lamps, both public and private.

I remember as a young teacher of French and astronomy, in the early 1970s, the delights of outdoor observing sessions after school; a 100 -year -old brass 4-inch (10 cm) refractor would make students exclaim in awe at the 2-million-year-old light from the Andromeda Galaxy; they would learn of the universality of gravitation while contemplating a colourful double-star system; and Galilee would live again as the moons of Jupiter were rediscovered. The school Astronomy Society no longer meets outside in the evenings. We have not lost the enthusiasm. We have lost the sky.

Canford Heath estate, one of Europe's largest housing developments, has gradually approached and enveloped my school. Vast numbers of globe-lights, poorly shielded street lamps and sports floodlights fill the sky with an unceasing orange and white glow. The school itself is surrounded by security lights, most of which shine above the horizontal. Light pollution is the child of wasteful attitudes. There can be no justification for sky glow; there are so many arguments against it. The British Astronomical Association's light pollution survey of 1990 found that over 90% of serious observers in the UK are affected, and satellite views of Europe by night confirm that the problem is similar in most countries. Calculating a general loss by exterior lighting of about 30% above the horizontal, we infer that it would be possible to light one town FREE by redirecting energy wasted from two other towns of similar size. At the EU/ESO conference in November 1994, it was encouraging to see such determination to give astronomy a higher profile in Europe's schools. We want to communicate our appreciation of the wonders of the cosmos to all children. We in Britain were very pleased to see units of astronomy entering a compulsory national curriculum a few years ago. Yet how can children be expected to appreciate what our Government's education department refers to as "the wider universe", if those children can hardly see it? Most schoolchildren live in towns and cities, and it is the town-dwellers who are being robbed of their heritage above. Here is one of the cruellest ironies in modern education. Teachers can be particularly sensitive to threats which civilisation lays before their disciplines, and they obviously have a vital role to perform in countering those threats. There is a great deal going on in Europe to protect the terrestrial environment, but there is widespread apathy and ignorance about light pollution and other threats to observing the universe. Should we not be adding our voices to those of that growing band of astronomers and environmentalists who are speaking out on behalf of the starry skies? Teachers can play their part by educating about sky glow, by pressing local authorities for action on stray light and energy waste, and by publicising the environmental aspects of a phenomenon which CAN BE REVERSED. Our children's children must never see the wonders of the night sky only in picture-books. They must never have to ask: "What were the stars?"

Bob Mizon is a teacher in Poole Grammar School, Dorset, UK.


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ANNOUNCEMENTS

The aim is to continue the work of our EU/ESO Workshop on the specific theme of training Science Teachers particularly in Astronomy. Many institutions which are concerned with this problem will be involved in the Workshop, both in the organisation and in the presentations.

Our new EAAE is largely represented with the president D.Simopoulos, the honorary president R.West, L.Gouguenheim, C.Romagnino in the standing committee, and me as chairperson (I hope provisional) in the organising committee.

The EAAE has now an important role in Europe and it is the first time that it is officially involved in an event. Therefore members are warmly invited to join the Workshop.

We hope that the large consent in the preparation is a positive signal for the success. We don't know now exactly how it will be formally organised but we intend to have a debate on European Science Teacher Training, especially in Astronomy, and a presentation of EAAE in the morning; in the afternoon surely a visit to the local facilities for teaching Astronomy and panel's talks, or panel's discussions or a magisterial lecture, or working groups always on subjects concerning teachers training.

Next week we have to decide and we will be more precise in the second communication. At the end buses are available to leave for Catania JENAM.

Anyhow please consider that the south of Italy is a very nice part of the world and in Reggio Calabria, and in Catania, there are very friendly people. In case that you plan a sort of tourist-business trip we will be very pleased to help you (contact me).

In Reggio Calabria a colleague, Angela Misiano Martino, has been acting in the field of teaching Astronomy for many years, and her work is there concretely visible in the large improvement of Astronomy both theoretically and practically with schools, use of telescope, planetarium, etc. She is also the chairperson of the local organising committee. And she likes to join the EAAE. I hope to have been able to convince you to attend the meeting. I look forward to seeing a great number of EAAE members in Reggio Calabria.

Best regards. Laura Abati


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Coming up in the next issue:


- Meteors and fireballs
- CCDs for amateur astronomy
- More about Internet
- HOU, Hands-on Universe
- More about the solar constant

...and much more, I hope, thank to your summer contributions!


Dead-line to turn your articles in: September 30., 1995

Please do not wait until the last minute if you think your article might need some "extra work" by the editor!

Instructions to authors

In order to make the edition of the Newsletter somewhat easier (and faster!), the authors should try to keep in mind the following recommendations:

Text: - please write in English (ask you local English teacher for corrections!)

- the Newsletter is published using Microsoft Word (5.1) on Macintosh, but any other text editor on Mac or PC is OK... Always join a paper copy (good quality!) of your article in case your diskette can't be read for one reason or another.

Figs.: - if the figures are "ready to edit", please keep their dimensions to something reasonable (use issue no.1 as an example) in order to save space in the Newsletter for other articles!

- if the original figures are too large, I can scan them to adapt their size, provided once again that the quality of the copy is of good.

- if pictures are to be included, think that the image has to be well contrasted in order to get a satisfactory quality of the scan.

In order to facilitate contacts when needed, please give a fax or phone number at which you can easily be reached.

Send your articles to:

Michael Reichen

home:
16, Avenue de Milan
CH - 1007 LAUSANNE
(tel: +41 21 616 75 82)

school:
CESSOUEST
Route de Divonne 8
Case postale 2214
CH - 1260 NYON 2
(tel: +41 22 361 24 37)
(fax: +41 22 361 04 85)

My e-mail address is michael.reichen@obs.unige.ch


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