Re: Equatorial monument in Brazil

[J.Tallman]

Hello Art,   "The rate of change of the declination at the equinoxes is 24 arc-minutes per day, approximately equal to the size of the image of the solar disk, so if the spot is perfectly centered on the line at dawn, by dusk it should be nearly off one side.  Actually, this is cool, because it means with appropriate and painstaking observations you can determine the moment of the equinox to within a few hours." Art Carlson   This is a very good point.  Unfortunately they were on site in May, I believe, and so there was no way to see the thing in action.  It was hard to estimate the size of the hole in the top of the stone tower because it was very high up and probably shot with a wide angle TV camera lense, but I'll bet the aperture was at least 8' in diameter.    The monument was interesting in its context as well.  On the one side (along the East/West axis) about 250-300 yards away was a football stadium with the Equator running exactly through midfield.  There were no bleachers on the monument side of the field.  On the opposite side of the tower was a very long street or walkway also following the equator.  The pedestrian plaza around the monument included a black stone strip inlayed into the pavement to indicate the exact position of the Equator.     I am sure the effect on the special days would be quite stunning, as long as the sun was shining in the rainforest!  I am surprised that I was able to find so little about it on the web!   Jim Tallman Sr. Designer FX Studios 513.829.1888