## Come in and join one of these projects!

If you decide to participate in this collaborative project within the Astronomy On-Line programme present yourself or your group. Your group and grouplocation will be entered on the map of Europe.

There are several projects you can take charge of:

### Lunar Distance

If you join this project read carefully how to perform the observations in such a way that they become useful for this project.

The detailed mathematics of the 2 Dimensional Eclipse method may be of interest, but is not needed in order to perform this experiment.
If you choose to use to help us measure the lunar distance, you should follow the eclipse as long as practically feasible.
Here is what to do.

Take a white piece of paper or a cardboard. Draw a circle, like below, and make careful centimeter markings.

What is the diameter "w" of this circle = _______________ ?

Now, place your cardboard in the light-beam of your binoculars, mirror or eclipse projector.

You have to adjust the distance, until the solar disc, or what is left of it, exactly matches the circle already drawn.

Now, measure the second parameter called "h" on the drawing above.

The circle diameter will of course stay fixed during the eclipse, but the value "h" will decrease dramatically.

Please notice, the value for "h" decreases when approaching the eclipse maximum. However, the value for your circle drawing "w" of course stays constant.
Write down the successive values for "h" as well as the accurate time, say every 5 minutes.

Here is an example of such a work: October 1996 example

The lowest possible "h/w" value occurs at the time of the eclipse maximum. From your graph and data, please determine the time of the eclipse-maximum, its corresponding "h/w" value as accurately, as you can.

During the October 1996 eclipse some very precise results were obtained by K4 Primary School classes, so even young children were able to get great results.

The implied math is within K12 level, however all groups will get their reported results back together with their calculated value for the lunar distance.

If you can have a sextant at your disposal you can measure the 'h' and 'w' values with great accuracy. Here you read how that is done!

### The Magnitude of the Eclipse

By definition the magnitude of a solar eclipse is the part of the solar diameter (not the solar disk!) that is eclipsed by the Moon.
A total eclipse has a magnitude of exactly 1 or more.
If you have found the smallest "h/w" ratio in the Lunar Distance project you can easily calculate the eclipse magnitude for your location:
Eclipse Magnitude = 1 - h/w

### The Size of the Moon

Almost everyone knows that solar eclipses occur because the Moon moves between the Sun and the Earth. But most people don't realise that total solar eclipses actually can occur because of the incredible coincidence that the Sun and the Moon appears to have the same size as seen from the Earth. In reality the Sun is 400 times larger than the Moon. But the distance to the Sun is also 400 times larger than the distance to the Moon.

In this combined solar and lunar photo (captured with a 500 mm telephoto lens during the eclipse week of October 1996) you can clearly see the practically equal size of Sun and Moon.

Measurements of the apparent size of the Moon can easily be done with a Pinhole Camera, binoculars or a telescope. If you combine these measurements with measurements of the lunar distance it is possible to calculate the actual diameter of the Moon.

### The EAAE 'Eclipse-Map' of Europe

The EAAE plans to publish a general map of Europe (if possible a satelite image made at the time of the eclipse!), showing the eclipse, as it was seen across our continent at the very same moment.
If you want your observations to be on that map: irrespective of where you live, make a drawing from your measurements and/or one photo at exactly

### 10.30 UT = 12.30 CEST (Central European Summer Time)

Don't forget to send your drawing or photo to the EAAE-Eclipse99 Project Group!

### Eclipse related Phenomena

If you are lucky to be within the totality, shadow bands, an eclipse related phenomenon, may become visible five minutes or so before the totality of the eclipse. These alternately dark and light bands are moving and look like the bands of light stripes at the bottom of a swimming pool. But they are much fainter! If you want to see this phenomenon you should spread out a large white blanket. Send us your impressions and measurements, like:

• what was the direction of the bands?
• in what direction were the bands moving?
• what was the speed of the moving bands?

Whether you live inside our outside the totality, also photograph your surroundings. How do these surroundings change, how do animals react? And what about your fellow observers: do they become 'be-eclipsed'?

### Eclipse Weather

Describe your feelings, does it become cold? Well, you may not be a objective thermometer so take 2 thermometers and place these in a height of 1.5 meter. One thermometer should be placed in shadow, one in sunlight.

Make current measurements of the sunlight- and the shadow-temperature every 5 minutes and send us a report. (Make also temperature measurements at the same time the day before or after the eclipse as reference!)

You can also measure the solar radiation. You can use the exposure-meter of a camera or you can build your own radiation-meter, like a Spanish group did during the 1996 eclipse.
If you also measure the h and w values as in the Lunar Distance project you can relate the amount of solar radiation with the fraction of the solar disk that is NOT covered by the Moon.

Another way to show the drop in solar radiation is making a photograph of your surroundings every 15 minutes. It is most important that you use the same diaphragm and shutter time for all exposures. The series of pictures will show dramatically what your eye can not detect objectively: the weakening of sunlight. Why? Your eyes will accommodate to the lower light intensity and give the impression that everything is normal. Only in the last few minutes before totality you will notice the drop in light.

The drop in temperature affects the air-pressure, wind, cloudiness etc. So if possible try to monitor these meteorological data. A phenomenon of interest is the 'eclipse-wind': often eclipse-observers noticed that shortly before totality this wind literally blew away the clouds blocking the Sun! But the opposite can happen when the drop in temperature causes a cloud cover to form if the humidity is high.

### Erathostenes revisited - Finding your own longitude & latitude

Within this project, you merely need a wooden plate and a nail. Mount the nail at right angles to the wooden plate and align this plate horizontally.

Now measure the height of your nail, and record the shadow movements every few minutes. (This may become difficult and a bit unprecise, while the sunlight is diminishing, however you should make sure to get measurements on both sides of the local noon).

Register the shortest shadow length obtained during that day as well as (if possible) the shadow length during the solar eclipse maximum itself. Please report nail height and shadow lengths values to the Eclipse Working Group.

In that way, combining measurements from several locations, we may even find the physical diameter of our own planet Earth, a parameter actually needed when determining the lunar distance.

If you desire you may:

a extend this method to estimate what astronomers call the solar declination (see the 2D math chapter).

b extend this method to the old "Jules Vernes" method. This may, by means of simple navigational math, tell your exact position longitude/latitude.

Report your values to the eclipse group.

Click on the line below in order to see what information you should mail to us as soon as possible after the eclipse:

Example of a report about the solar eclipse

Good luck and have a nice hunt!