Mississauga Centre RASC

80th Meeting

                                                                                                 Speakers’ Night       

 

 

Day:                Friday March 9, 2007

 

Chair:                Randy Attwood

 

Speaker:          Peter Broughton

 

                       

Randy Attwood spoke about the book “Complete Idiot’s Guide to the Sun” of Jay Pasachoff, of the “Globe at Night” website, and about the recent lunar eclipse.

 

 

A Brief History of Astronomy in Canada  1608-1900

 

Peter Broughton, member of the Toronto Centre RASC, former National Secretary and President, member of the Natural History Committee, and author of “Looking Up” written to celebrate the 100th anniversary of the Society, spoke about astronomy history in Canada from 1608 to 1900. 

In the year 1608 when the telescope was invented, Champlain founded Quebec, the oldest continually inhabited city in North America. An astrolabe possibly belonging to Champlain was described.

Most of the astronomy during the period in question involves measurement of latitude and longitude. Latitude is easy to measure and could be established to seconds of arc by the late 1700’s.

In the 1600’s, arctic explorers such as Baffin and James made longitude measurements. Thomas James spent the winter on Charlton Island, timed the lunar eclipse of 1631 and found longitude measurements to an error of ¼ degree. His observations were praised by Horrocks and Hooke. He used a quadrant, staffs and other instruments.

In New France, the Jesuit missions, established in 1625, taught hydrography, navigation and mathematics. Lalemont, the superior, observed partial solar eclipses in 1663, 1670, 1679 and measured the degrees of the eclipses. He timed the beginnings and endings and was able to calculate the time with 4 minutes of error on average, corresponding to a 1 degree error in longitude. This was largely due to the inaccuracy of the ephemeredes.  The Jesuits also observed and drew 3 comets.

At Ste. Marie among the Hurons near Midland, a display shows astronomical instruments such as the cross-staff for Sun-Moon distance, back staff for solar altitude, astrolabe, hour glass. Joseph Bressani, a missionary at Ste. Marie timed lunar eclipses, they being the simplest way to calculate longitude.  His observations had errors of only a few minutes. Bressani conducted the earliest telescopic observations in Canada in 1646. In 1642, B. Vimont stated that the Moon disappeared completely during eclipse. Deshages’ 1685 lunar eclipse observation was considered definitive by J. Cassini of the Paris Observatory.

Peter then described coastal exploration from 1758 to 1790.  After defeating the French in 1759, the British explored their new territory. Samuel Holland and James Cook surveyed the St. Lawrence River; Cook explored the east and west coasts.  Holland, surveyor general of North America observed the annular eclipse of Aug. 5, 1766 while Cook observed it as partial in Newfoundland.  The transit of Venus was observed by Holland in Quebec, by Cook in Tahiti and by William Wales in Churchill. Using a Gregorian telescope and quadrants for Jupiter satellite observations, Samuel Holland calculated the difference in longitude for two people by using the local time difference of the events. A tent-like shelter was used to house the instruments in the temperate climate. 

 

The Hudson Bay Company was forced to move inland by trade conditions and sent out surveyors from 1778 to 1820. David Thompson measured the solar altitude using an artificial horizon with the Sun reflected in mercury.  The 12-inch Dolland was able to read to within 15 arcsec of precision.  D. Thompson’s latitude measurements were done to a precision of 10 arcsec standard deviation and the mean to within 1 arcsec of the modern value. Longitudes measured by the Sun-Moon distances by D. Thompson had errors of 60” to 90”.  Peter Fidler did occultation timings on the prairies from 1792 to 1820 to find longitudes, but he was also interested in observing and made diagrams of eclipses and other phenomena. His solar eclipse observations were remarkably accurate. Using telescopic observations of Jupiter and its satellites, he was able to calculate longitude within 10 min of arc.

 

In the period 1833 to 1867, loyalists immigrated to Canada. Various colleges taught astronomy, books were written and observatories set up.  In Kingston, Murray Tower was built and the annular eclipse of 1854 observed. The City Observatory built in 1856 and now part of Queens University has a 6 1/4 “ Clark refractor.  In the 1850’s, observatories were established in Toronto, Montreal, and Quebec where a time ball was released for ships to set their chronometers, and a maritime observatory in Halifax.  The books “Astronomy”, “God’s Glory in the Heavens”, “Astronomical Philosophy” from 1836 to 1862 were written by ministers to celebrate God’s creation.  Amateur observatories rose from 1868 to 1905. In Victorian times, women were prominent in natural history societies and it was considered proper for them to sketch the Moon.  Arthur Miller in Toronto in the 1890’s took pioneering photographs – the first stellar photo in Canada in 1893, Cassiopeia, and stellar spectroscopy.

 

1905 was a pivotal year in astronomy.  C.A. Chant established the astronomy option at the University of Toronto in order to train astronomers for the Dominion Observatory which was set up in that year.  The DAO directors King and Klotz were firmly grounded in surveying but felt the need for pure astronomical research. The observatory sported a 15” Brashear refractor with a spectrometer and camera.  Many papers were published in the first ten years on numerous topics and with numerous citations in other journals. Also in 1905, the Canadian Eclipse Expedition was sent to Labrador (unfortunately clouded out) and included Chant and Plaskett, the 2 most important astronomers early in the century.

 

Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to Miss Centre. meeting reports page
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