Location : In the south-west of France countryside (3.000 inhabitants) . 17 km from Montauban (50.000 inhabitants), 70 km from Toulouse (650.000 inhabitants)

Grade and/or Subject Area 12 students from 10 to 15 years old, of the astronomy club of the school are working during the lunch pause. The solar noon is calculated from an ephemeride.

Winter :

Students have been drawing a meridian line, using the corner of a window as the extremity of the gnomon

Springtime :

measurements with a one meter gnomon.

SSummer solstice week :

measurements with the gnomon and the quadrant. Useful length of the gnomon: 882mm, which is also the radius of the quadrant. (precision +/- 00°05’)

Our blog is http://eratostwin.blogspot.com/

The highlights :

15th march:

Ides of March. Brutus was in a bad mood. Céline is the president of the students. She avoided his sword. At least, she realised these measurements.

Solar midday: 13:04 (TU+1) Gnomon: 1,00m Shadow: 1,05m Angle of sun: 46°24’

Partner: tropic of Cancer
(Angle of sun: 25°41’ Distance to Lafrançaise: 2298 km)
Circumference: 2298 x 360 / (( 46 + 24/60 ) - ( 25 + 41/60))=
2298 x 360 / (46,400 – 25,683) = 39.932 km

Partner: Hoboken,NJ, USA
(Day : 19th march, Latitude: 40,74 N, Angle of sun: 40,5° , Distance to Lafrançaise: 377 km)
The calculation with those measurements is not precise:
 There is a delay of 4 days between the measurements. This is too long.
 A distance of 377 km between the parallèles of the cities is too short.

Summer solstice:

videoconference with Alexandria Library (Egypt) on june 21st to commemorate Eratosthenes measurement.

Angle of sun: 20°40’ = 20,667°
Partner: tropic of Cancer(Angle of sun: 00°00’,
Distance to Lafrançaise: 2298 km)