1. Which procedures do we have within our reach to observe the eclipse?

- You must NEVER look at the sun without any protection; it is very pernicious for the sight.  The eclipse does not even have to be looked at when it is in an advanced period and the sunlight is reducing since serious ocular damages could happen. To observe the  solar eclipse five different methods have been used:
-  Special glasses, which are made out of standardized filters, which prevent from the harmful sunbeams, and a  cardboard contour. This can be seen in  fig.2.
- Video camera  protected with a number 14 lead base soldering filter, which has the same function as  the glasses of standardized filter. This can be seen in  fig.3.  

-  Thermoplastic soldering mask, which is composed of a  fixed, small and rectangular window with a special glass which absorbes the ultraviolet radiation. This can be seen in fig.4.
- If we do not have either any glasses or any system, two sheets of cardboard can be used instead. In one of them a small hole must be made and the light of the Sun that passes through this small hole has to be projected on the other sheet. This can be seen in fig.5.

Fig. 4 Mechanical students with soldering masks	Fig. 5 Method with cardboards	Fig. 6 Projection of the eclipse through the leaves of the school playground trees.

Sequence of the annular eclipse - Sony Digital Video Camara - LLeida (41º 37' 37'' N, 0º 36' 52´´ E, 170 m)

2. Which distance must  the Moon be situated from the Earth in order to produce a total eclipse of Sun in a detreminate point of the Earth?

- In order to answer this question, we’ll suppose that the moon is aligned between the Earth and the Sun and in the same plane. Furthermore we’ll suppose that the sunlight propagates in the space in straight line).
Data:
Sun’s radius (S) = 696 000 km
Moon’s radius (L) = 1738 km
Average distance from the Earth to the Sun (ds) = 149.600.000 km

Figura 7.  Relative position of the Earth, the Moon and the Sun in a total  Sun’s eclipse

Applying the Thales’ theorem:

The distance where the moon has to be  from the Earth at the moment  the total eclipse is produced  can be calculated .

dl = 373.570 km

If the moon is situated near  the apogee (405.500 km), the eclipse will be annular.

3. How can the distance to the Moon from the Earth be  experimentally determined -from the observation of the annular eclipse of Sun on 3rd  October, 2005?

-  To determine  experimentally the distance to the Moon  from the Earth the eclipse’s day, we will base upon the shot taken by Josep Masalles Roman at Villagordo del Cabriel (39º33'10" N - 1º28'26" W - 699 m) (fig.8). This photograph was taken by fitting together one Reflex camera to a telescope Meade ( D:125 mm,  F:1250 mm).

Figure 8. Annular eclipse	Figure 9. Meade Telescope

- Doing a picture treatment with the Paint Sho Pro program we can obtain the percentage of the Sun’s diameter eclipsed by the moon.

Figure 10. Image treachment with  Paint Shop Pro program

- Now we’re going to measure the apparent diameters of the Sun and the Moon from the differences of the axis (x, y)  of the extreme points.
- The obtained results are:

	Apparent radius (length’s units)
Sun	341
Moon	326

Figure 11. Moon’s position in a total Sun’s eclipse

Figure 12. Moon’s position in an  annular solar eclipse

Applying again the Tahles’ theorem on the figures number 11 and 12 the following equalities are obtained:


The following conclusion can be inferred:

 4. How does the temperature change during  the eclipse? How does the intensity of the sunliht change during  the eclipse?

Material:
The material used in this practice  at  the  schoolplayground  is:

•  Temperature sensor with a sensibility of 0,001 ºC
•  Light sensor with a sensibility of 0,001 Klx
•  MultiLog PRO keyboard
•  Two supports with nuts and two tweezers
•  In the classroom .
•  A computer with the MultiLab program is required

Assembly:
The assembly of all the device has  to be done on this way:
    1st: In order to fasten the sensors, they have to be fixed by an adjusting nut, and all this  must be fixed  too  to the  tweezers which will be tied up to a base.(fig.1)
    2nd:- Connect two sensors with the MultiLog PRO  keyboard
    3rd: -Turn on the keyboard and select the capture mode, in this case, one sample per each second during 10.000 seconds.
          -Start measuring at the beginning of the eclipse and stop once it has finished.
    4th:-Download and analyse the data in the computer with the MutiLab progamm’s  help.

- PHOTOGRAPH OF THE ASSEMBLY:

Figure 13.  Assembly Experience

- Data treatment:
Both, the  data of temperature and  light intensity must be downloaded and  checked.
- Taking into account that we started registering the  data at 07:41am, we can know the exact time  when the Moon  was totally opposite the Sun and thus when the annular eclipse was produced, at 09:01am . While commuting the first and the second cursor  at  the beginning and in the middle  of the eclipse the descent of the intensity of light and the descent of temperature produced can be measured. (Fig.14 and 15).

Figure 14. graphic 1	Figure 15. graphic 2

- (As far as the  light data   are concerned  we have to bear in mind that normally the light intensity is higher as the day  advances;and for this reason, after the eclipse there is more light than at the beginning.
Not too much care must be given to the temperature data  when wind gales are produced  because they  might cause some modifications on them)

- Sunlight intensity:
Maximum intensity: 9’315Klx
Minimum intensity: 1,215 Klx
Variations: Dllum = 8,1Klx => 87%                                

From  the beginning to the moment  when the annular eclipse took place , a descent in the intensity  of light was produced- that is to say-   a 87% less.

- Temperature:
Maximum temperature: 13,32 ºC
Minimum temperature: 11,799 ºC
Variation: Dt = 1,128 ºC => 8,47%

From the beginning to the exact moment of the annular eclipse the temperature has fallen  1,128ºC.  we are talking about a reduction of an 8,47%

5. How do dampness and speed wind change during  the eclipse?

- We have been able to observe that there was a reduction in the temperature and the intensity of light, and also in the dampness and the wind speed. The meteorological observatory of the city of Lleida gave us some information that was recorded during the eclipse. (Look at fig. 16a, 16b and 17).  The information had been taken in solar schedule,. -two hours less than the time established in our zone.

Fig.16a.  Dampness graphic        Fig.16b. Temperature graphic

- Figure 16 shows us the  air dampness  and temperature descent. Knowing that
these two factors were linked,  we already supposed that a decrease in the air’s dampness will be produced- since a reduction of 1 degree  took place during the eclipse.

	In figure 17 we can see the wind speed during the annular eclipse. With this graph we can know that a reduction in the wind speed took place. This fact happens because the air moves quicker if the weather is hotter. However, as the temperature lowered an 8'47 % the air masses moved less and slowier.
Fig.17. Information about the wind speed