Historical astronomy - finding Mars parallax and distance

I just finished reading Arthur Berry's _A Short History of Astronomy_
(1898, 3d 1961). Berry reviews the major astronomical accomplishments
through the end of the 19th century. Berry mentioned that in addition
to the transit of Venus, the parallax of Mars at opposition was also
used in the 1870s to establish an Earth-Mars distance and by Kepler's
Third Law, the Earth-Sun distance. Berry at Chap. XIII, Sec. 281.
Earlier measurements were made in the 1670s. Berry at Chap. VII, Sec.
161.

This suggests that modern amateurs equipped with CCDs and web cams
could replicate the experiment and measure the parallax of Mars using
an Earth baseline during the Oct 30, 2005 greatest size and/or Nov. 7,
2005 opposition of Mars.

Pete Lawrence restaged a similar historical experiment to find the
parallax and distance of the Moon using the Nov. 8, 2003 and Oct. 28,
2004 lunar eclipses.
Lunar Parallax Demonstration Project
http://www.digitalsky.org.uk/lunar_parallax.html

Two techniques have been used to measure the parallax of Mars.

The first involves an Earth baseline and two observers. This method
was first used by Cassini, Picard and John Richer during 1671-1673.
Richer traveled to Cayenne (lat 5 deg) while Picard and Cassini
observed from a newly completed observatory in Paris. Chap. VII, Sec.
161. This provided a north-south baseline on which the observers could
make a position observation at the same time - opposition.

The second technique, called the diurnal method, involves one observing
station measuring Mars' position on the night of opposition at
different times. The changed position of the OP over time resulting
from the Earth's rotation provide the baseline. This technique was
invented by Flamsteed (1646-1720) and was revived by Sir George Airy
(of the Airy Disk) in 1857. In 1877, a Dr. "Gill" working at Ascension
used the diurnal method to measure the parallax of Mars at opposition.
Berry at Chap. XIII, Sec. 281.

The current Mars opposition occurs on Nov. 7, 2005. At that time, Mars
will be about 69,415,600 km (43,132,800 miles) from the Earth. Using
the half-angle formula, those distances suggest a parallax at
opposition on a 6,000 kilometer baseline of 2.8 arcsecs, or on a 12,000
km baseline of 5.6 arcsecs.

A similar educatonal project was undertaken by the Univ. of Chicago
Yerkes Observatory Hand-On-Universe outreach program for the 2003 Mars
opposition. That project used the diurnal method. The project
documentation is here -
http://sunra.lbl.gov/~vhoette/Explorations/MarsParallax/
including a useful spreadsheet on computing the size of the baseline
for the diurnal method.
http://sunra.lbl.gov/~vhoette/Explorations/MarsParallax/docs/

Just an idea and suggestion.

- Canopus56

.

Relevant Pages

  • Historical astronomy - finding Mars parallax and distance
    ... the parallax of Mars at opposition was also ... could replicate the experiment and measure the parallax of Mars using ... The first involves an Earth baseline and two observers. ...
    (sci.astro.amateur)
  • Re: Mars this summer
    ... Mars Opposition, November 6-7, again depending on your location. ... difficult to see for northern observers. ... The Mighty Light of ten thousand suns ...
    (sci.astro.amateur)
  • Re: Martian "Canals
    ... You think that those observers who reported and documented linear ... see or report 'linear' structures. ... were evidence of the seasonal grow and retraction of plant material on Mars, ...
    (sci.astro.amateur)
  • Re: Mars
    ... Mars was at a very favorable opposition in August of 2003. ... Opposition is the time when Earth overtakes Mars in its orbit. ... little further from the sun during July. ...
    (rec.outdoors.rv-travel)
  • Re: Today Mars is the Brightest and at Opposition to Earth !
    ... >> Today Mars is the Brightest and at Opposition to Earth! ... >> east just as the sun sets in the west. ... >> orbits are actually elliptical, ...
    (sci.astro.amateur)