Mississauga Astronomical Society

Twentyfirst Meeting

Members’ Night

 

Day:                Friday, May 7, 2004

 

Chair:         Ian McGregor

 

Speakers:   Jim Jackson

                   Dan Doolan

Randy Attwood

                    

                              

Ian McGregor remarked on three events of the past week: the total lunar eclipse of May 4, Space Day on May 6 and the first appearance of Comet NEAT on May 6.

 

Transits of Venus   

Jim Jackson spoke about the historical aspects of Venus transits. A Venus transit is a rare and beautiful event. Only 5 have ever been seen in history. Transits have a rich and colourful history and each is an archive of what was occurring in the history of that time.

In mediaeval and latter times, one school of thought which included Hipparchos, Aristotle, Tycho, the Church claimed that the Earth does not move. On the other hand, the heliocentric theory was supported by Aristarchos, Galileo, Copernicus, Kepler, Newton and Milton. Stellar parallax was too small to measure and decide the answer, but it was feasible to measure the parallax of Venus using transits and Kepler’s law of relating distance and period. 

 

There were two transits in the 17th century: 1631 and 1639. Historically around this time Kepler had formulated his laws of motion, Newton the law of gravity, calculus, and he wrote the Principia Mathematica.  The first known observation of a Venus transit was made in England by Horrocks and Crabtree in 1639.

 

In the 18th century there were transits in 1761 and 1769. This was the time of Herschel’s telescope, the rise of steam power, experiments with electricity and magnetism and Linne’s biologic theory. Edmund Halley developed a method to calculate the parallax of Venus using the transit  but he died in 1746 before he could see his method tested.

8 nations participated for the 1761 transit, with James Cook in Tahiti, Mason and Dixon in South Africa. Most dramatic is the story of Le Gentil who determined to measure the scale of the universe. He was unable to make useful observations on a ship in the Indian Ocean in 1761; he was thwarted eight years later by clouds, and he endured a shipwreck on his way back to Europe.  

 

19th century transits occurred in 1874 and 1882. This was the age of certainty with Dalton’s atomic theory, Joule and conservation of energy, Darwin and evolution, Clausian entropy, Maxwell’s electromagnetism, Pasteur’s bacterial theory, Roentgen rays and the ascendancy of mathematics. 7 countries mounted  62 expeditions in 1874. There were difficulties in measurements and the parallax method was questioned as to its usefulness but a parallax of 8.883 was obtained in 1882 (current value 8.794).  

 

The 20th century had no transits of Venus. This is the age of Einstein with his relativity, Rutherford and the atom, Heisenberg’s uncertainty principal, Schroedinger’s wave equation, Dirac’s quantum mechanics, Hubble’s recession laws, the Big Bang theory, Guth’s inflationary universe and space based observations.

 

In the 21st century there are transits in 2004 and 2012. Of note, on Nov. 10, 2084, a transit of Earth will be visible to Martian colonists. Jim’s main comment about these Venus transits was: “Don’t miss them”.   

 

Digital Imaging Processing Webcam with Registax

Dan discussed Registax, a freeware program for bringing out images from webcams. Advantages of webcams include low costs, lightweight cameras, ability to “freeze” atmospheric conditions, and ability to stack frames to reduce noise in the final product. Registax at http://aberrator.astronomy.net/registax/ is able to select the best images from a video, align, combine and process them (tutorial at http:www.threebuttes.com). Wavelet processing can bring out detail in the images. However the program cannot compensate for poor seeing, focus, poor optics or tracking.

 

Dan demonstrated the creation of fabulous images of Jupiter and Saturn from raw video footage using Registax. He also showed an example of a Jupiter animation using the same program.  Dan told the group that using webcam imaging is like upgrading one’s telescope by 50% and he encouraged people to try this modality.

 

Mars Exploration Video

Randy Attwood showed the latest video from the Mars Rover from the NASA press conference of May 6.  The rover Opportunity has reached Endurance Crater and taken a spectacular image of it. Meters of bedrock are exposed here in contrast to the centimeters at the original landing area. Although this exposed stratigraphy is exciting to study, the cliffs present a danger of falling to the rover. Opportunity will thus traverse around the crater, attempt to find safe access to the rocks of the outcrop and study the crater. The mission engineers demonstrated how the path of the rover and driving sequences are planned.

 

 Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to M.A.S. meeting reports page
Mississauga Astronomical Society