The Mars Parallax Project
The Earth’s opposition with Mars on August 28, 2003 occurred only 41 hours before the Mars perihelion, reportedly the closest we have been to Mars at opposition in some 60,000 years.
This was the optimum time to measure the parallax angle of Mars from Earth, in order to calculate the distance to the Sun as first done by John Flamsteed in 1672.
This article describes the most recent efforts reproduce the experiment performed by John Flamsteed almost 450 years ago. The effort demonstrates the remarkable technique and skill that was required of Flamsteed to make such measurements with the technology available at the time.
The work reported in this article is a continuation of the project initiated by Dr. Moreland in 2001, using an improved micrometer eyepiece, and taking measurements with Mars at its optimum position relative to the Earth. Based on the parallax measurements of Mars, taken on September 16-17, 2003, the astronomical unit (the distance from the Earth to the Sun) was calculated to be 94.2 million miles +/- 9 million miles.