The 1999 Mensa Total Eclipse Party
Wednesday 11th August 1999; Rethel, France

Celebrate the last total eclipse of the millennium with the party to end all parties!

On Wednesday 11th August 1999 the last total solar eclipse of the millennium will occur, which (weather permitting) will be visible from much of northern Europe.

While the partial eclipse may be seen from virtually the whole of the northern hemisphere, the actual path of totality will clip the tip of Cornwall and then track through France north of Paris, over Reims, Metz and Strasbourg, and on into Germany and Austria before heading down towards India via the Balkans and the Middle East.

It is planned to celebrate this unique event with a party near Rethel in northern France. Rethel is close to the eclipse centre-line and within easy reach of the Channel ports. The party will be based around a traditional French 'mechoui' (basically, a large barbecue with a whole lamb or mutton roasted on a spit over a fire pit).

You are invited to gather at the party site from about 10am (French time) in time to see the start of the partial eclipse which will last about 2 to 3 hours. The actual total eclipse will last approximately 2 minutes and will start at about 12:30pm local time. Brilliant sunshine (except during the eclipse, of course) and good weather throughout the day have already been ordered in abundance.

In the highly unlikely event of bad weather (remember this is summertime in northern Europe!), we'll scrub watching the eclipse and just get on with the party (inside a marquee, if its raining). Preparations for the mechoui will start as soon as practical after the eclipse, and the party is expected to go on well into the evening (to give those who want to plenty of time to get totally eclipsed!). It is hoped that Mensans from across Britain, Ireland, Europe and anywhere else (including Alpha Centauri) will come and join in the fun.

For those of you who want to make more of an expedition of this event (i.e. a few days holiday), there are plenty of things to see and do around Rethel.

Party Arrangements

The actual party site is at Pargny Resson, approximately 3km east of Rethel along the D30 (see map below).

Entrance to the party is by ticket only. The cost of each ticket is:

* 22 Euros per person if booked before 1st March 1999 * 33 Euros per person if booked after 1st March.

The entrance fee includes food from the mechoui and a glass of wine. Normal party rules also apply; so BYOB, BYOF, etc. Extra wine, beer or champagne may be purchased on site. On site parking is available for a nominal fee of 20FF.

There is a maximum limit of 300 persons for the party. Bookings will be accepted on a first-come, first-served basis.

Cheques to the appropriate value in Euros should be made payable to B Colman, and sent to B Colman, 18 Tressel Drive, Sutton Manor, St Helens, Merseyside, WA9 4BS, United Kingdom. Include a stamped, self addressed envelope for your receipt and a map of how to get into the party site.

Accommodation and Travel

It is your responsibility to book your own accommodation and travel.

There is a wide range of accommodation available in the Ardennes near Rethel; including Hôtels, Camp Sites, Gîtes Ruraux (self-catering accommodation), Chambres d'Hôtes (bed and breakfast), Tables d'Hôtes (guest houses), Bateaux Habitables (houseboats), Gîtes d'Enfants (accommodation catering for families with children) and Hebergements de Groupe (accommodation for groups). A brochure on Gîtes Ruraux, Chambres d'Hôtes and Gîtes d'Enfants in the Ardennes may be obtained from

Gîtes de France Ardennes Service Reservation 1 Avenue du Petit Bois BP 331 08105 Charleville-Meziers Cedex Tel: +0033 (0)3 24 56 89 65 Fax: +0033 (0)3 24 56 89 66

The brochure costs 35FF (credit cards and eurocheques are accepted.) and contains details of the accommodation costs, and how to book. Further information on accommodation including Camp Sites and Hôtels may be obtained from

Comité Départemental du Tourisme des Ardennes 22/24 Place Ducale 08000 Charleville-Meziers Tel: +0033 (0)3 24 56 06 08 Fax: +0033 (0)3 24 59 20 10

Tourist information for the Ardennes may be obtained from the following addresses:

French Tourist Office Maison de la France 178 Picadilly 21 Avenue de la Toison d'Or LONDON W1V 0AL Tel: 0891 244 123 1060 BRUXELLES Tel: 0902.88.025

Französisches Fremdenverkehrsamt Frans Verkeesbureau Postfach 100 128 Prinsengracht 670 60001 FRANKFURT/MAIN 1017 KX Amsterdam Tel: 0900 112 23 33 Tel: 0190/599061

Getting to the party site is likewise your own responsibility. Some attractive travel offers are available for those booking early. For example, for those travelling from the United Kingdom:

* Seafrance Ferries (telephone 0990 711711) are offering a 5 day return ticket for £45, for 1 car and up to five persons.

* Le Shuttle (telephone 0990 353535) is offering a 5 day return ticket for £79, for 1 car and up to nine persons.

Both offers are valid up to 31st December 1998. Please note, no responsibility is accepted for the accuracy of this information.

Other Activities

Monday 9th August 1999: Canoe trip to Rethel from Anseremme, near Dinant, Belgium. Contact Bernard Colman (+0044 [0]1744 815000) or Steve Nelson (+0044 [0]1539 533517) for further details.

Tuesday 10th August 1999 (Afternoon): Visit to a Champagne Cave near Reims. Contact Bernard Colman (+0044 [0]1744 815000) or Steve Nelson (+0044 [0]1539 533517) for further details.

Wednesday 11th August 1999 (Evening): It is hoped to have a presentation "Night of the Shooting Stars" by the French Centre Scientifique Argos. Contact Bernard Colman (+0044 [0]1744 815000) or Steve Nelson (+0044 [0]1539 533517) for further details.

Further Information on the Eclipse

See the attached sheet for some basic advice on the safe viewing of the eclipse, photography, duration of the partial and total eclipse phases, etc. For full details about the 1999 eclipse, and others up to the year 2020, visit the NASA website

Time of the Eclipse: Universal Time or UT is the precise measure of time used as the basis for all civil time-keeping. Although exact definitions differ, it can be assumed that Universal Time is equivalent to Greenwich Mean Time or GMT.

Like most astronomical calculations, eclipse predictions are usually presented in terms of Universal Time. In order to convert eclipse predictions from UT to local time, you need to know what time zone you are in. For the total solar eclipse of 1999, the path of totality passes through a number of time zones and the conversion from UT to local time is as follows:

* United Kingdom = UT+Daylight Saving * Central Europe = UT+Daylight Saving + 1 hour

For the UK and France, Daylight Saving = 1 hour. The eclipse at Rethel is predicted to occur at approximately 10:25 UT. Taking into account the Central European Time Zone and Daylight Saving, this equates to about 12.25pm local time.

Eye Safety During Solar Eclipses (Edited from the Espenak/NASA Web Page)

The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse. Partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions. Even when 99% of the Sun's surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection. Do not attempt to observe the partial or annular phases of any eclipse with the naked eye. Failure to use appropriate filtration may result in permanent eye damage or blindness!

Generally, the same equipment, techniques and precautions used to observe the Sun outside of eclipse are required for annular eclipses and the partial phases of total eclipses. The safest and most inexpensive of these methods is by projection, in which a pinhole or small opening is used to cast the image of the Sun on a screen placed a half-meter or more beyond the opening. Projected images of the Sun may even be seen on the ground in the small openings created by interlacing fingers, or in the dappled sunlight beneath a leafy tree. Binoculars can also be used to project a magnified image of the Sun on a white card, but you must avoid the temptation of using these instruments for direct viewing.

The Sun can be viewed directly only when using filters specifically designed for this purpose. Such filters usually have a thin layer of aluminum, chromium or silver deposited on their surfaces that attenuates both visible and infrared energy. One of the most widely available filters for safe solar viewing is a number 14 welder's glass, available through welding supply outlets. More recently, aluminized mylar has become a popular, inexpensive alternative. Mylar can easily be cut with scissors and adapted to any kind of box or viewing device. A number of sources for solar filters are listed below. No filter is safe to use with any optical device (i.e. telescope, binoculars, etc.) unless it has been specifically designed for that purpose. Experienced amateur and professional astronomers may also use one or two layers of completely exposed and fully developed black-and-white film, provided the film contains a silver emulsion. Since all developed color films lack silver, they are always unsafe for use in solar viewing.

Unsafe filters include color film, some non-silver black and white film, medical x-ray films with images on them, smoked glass, Photographic neutral density filters and polarizing filters. Solar filters designed to thread into eyepieces which are often sold with inexpensive telescopes are also dangerous. They should not be used for viewing the Sun at any time since they often crack from overheating. Do not experiment with other filters unless you are certain that they are safe. Damage to the eyes comes predominantly from invisible infrared wavelengths. The fact that the Sun appears dark in a filter or that you feel no discomfort does not guarantee that your eyes are safe. Avoid all unnecessary risks. Your local planetarium or amateur astronomy club is a good source for additional information.

In spite of these precautions, the total phase of an eclipse can and should be viewed without any filters whatsoever. The naked eye view of totality is completely safe and is overwhelmingly awe-inspiring!

Solar Eclipse Photography (Edited from the Espenak/NASA Web Page)

Solar eclipses may be easily photographed provided that basic eye safety precautions are followed. Almost any kind of camera with manual controls can be used to capture this rare event. However, a lens with a fairly long focal length is recommended to produce as large an image of the Sun as possible. A standard 50 mm lens yields a minuscule 0.5 mm image, while a 200 mm telephoto or zoom produces a 1.9 mm image. A better choice would be one of the small, compact catadioptic or mirror lenses that have become widely available in the past ten years. The focal length of 500 mm is most common among such mirror lenses and yields a solar image of 4.6 mm. With one solar radius of corona on either side, an eclipse view during totality will cover 9.2 mm. Adding a 2x tele-converter will produce a 1000 mm focal length, which doubles the Sun's size to 9.2 mm. Focal lengths in excess of 1000 mm usually fall within the realm of amateur telescopes. If full disk photography of partial phases on 35 mm format is planned, the focal length of the optics must not exceed 2600 mm. However, since most cameras don't show the full extent of the image in their viewfinders, a more practical limit is about 2000 mm. Longer focal lengths permit photography of only a magnified portion of the Sun's disk. In order to photograph the Sun's corona during totality, the focal length should be no longer than 1500 mm to 1800 mm (for 35 mm equipment). However, a focal length of 1000 mm requires less critical framing and can capture some of the longer coronal streamers. For any particular focal length, the diameter of the Sun's image is approximately equal to the focal length divided by 109.

A mylar or glass solar filter must be used on the lens throughout the partial phases for both photography and safe viewing. These filters typically attenuate the Sun's visible and infrared energy by a factor of 100,000. However, the actual filter factor and choice of ISO film speed will play critical roles in determining the correct photographic exposure. A low to medium speed film is recommended (ISO 50 to 100) since the Sun gives off abundant light. The easiest method for determining the correct exposure is accomplished by running a calibration test on the uneclipsed Sun. Shoot a roll of film of the mid-day Sun at a fixed aperture (f/8 to f/16) using every shutter speed between 1/1000 and 1/4 second. After the film is developed, note the best exposures and use them to photograph all the partial phases. The Sun's surface brightness remains constant throughout the eclipse, so no exposure compensation is necessary except for the narrow crescent phases which may require two more stops due to solar limb darkening. Bracketing by several stops may also be necessary if haze or clouds interferes on eclipse day.

Certainly the most spectacular and awe inspiring phase of the eclipse is totality. For a few brief minutes or seconds, the Sun's pearly white corona, red prominences and chromosphere are visible. The great challenge is to obtain a set of photographs which captures some aspect of these fleeting phenomena. The most important point to remember is that during the total phase, all solar filters must be removed! The corona has a surface brightness a million times fainter than the photosphere, so photographs of the corona are made without a filter. Furthermore, it is completely safe to view the totally eclipsed Sun directly with the naked eye. No filters are needed and they will only hinder your view. The average brightness of the corona varies inversely with the distance from the Sun's limb. The inner corona is far brighter than the outer corona. Thus, no one exposure can capture it's the full dynamic range. The best strategy is to choose one aperture or f/number and bracket the exposures over a range of shutter speeds (i.e. 1/1000 down to 1 second). Rehearsing this sequence is highly recommended since great excitement accompanies totality and there is little time to think.

Finally, an eclipse effect that is easily captured with point-and-shoot or automatic cameras should not be overlooked. Use a kitchen sieve or colander and allow its shadow to fall on a piece of white card-board placed several feet away. The holes in the utensil act like pinhole cameras and each one projects its own image of the Sun. The effect can also be duplicated by forming a small aperture with one's hands and watching the ground below. The pinhole camera effect becomes more prominent with increasing eclipse magnitude. Virtually any camera can be used to photograph the phenomenon, but automatic cameras must have their flashes turned off since this would otherwise obliterate the pinhole images.