Mississauga Centre RASC

96th Meeting

                                                             Speakers’ Night       

Day:                Friday December 14, 2007

Chair:                Randy Attwood

Speaker:          Ian Shelton

The Uncertain Future of the David Dunlop Observatory

Ian Shelton, discoverer of supernova 1987A, has been involved in public outreach at the DDO.  He spoke about the history of the institution.

The DDO spans the whole era of modern astronomy.  It began with Dr. C.A. Chant, a schoolteacher in Markham who received his degree at King’s College which became the Department of Astronomy in 1905.  Chant was driven to publicize astronomy and gave many talks.  One of these talks was attended by David Dunlop, a wealthy and well-connected lawyer who became interested in helping build a large telescope in the eastern part of North America.  After Dunlop died in 1924, Chant approached his widow Jessie with the idea of constructing a monument to her late husband in the form of a large observatory. It was a huge project. Land was acquired in 1928 in Richmond Hill and construction begun in 1930.  The telescope was built in England by Grubb and Parsons.

The primary mirror was made in the USA by Corning in New York with cutting edge technology at the time. It was the first large use of pyrex glass, 2 tons, 76 inches (1.88 metres) in diameter and 12 inches thick.  It was shipped to England for grinding. The 80 ton dome with copper on iron was built in England, erected there, disassembled and rebuilt in Canada. The telescope was dedicated in March 1931 becoming the second largest in the world – after the 100 inch.  Of the two major foci, the f/5 Newtonian focus at 30 min of arc was used directly and the f/8 Cassegrain focus at 2-4 seconds of arc was used for spectroscopy.

Helen Hogg used the Newtonian focus for her observing of RR Lyrae stars in globular clusters.  These are very useful as standard candles but not as bright as Cepheids.  In addition, a 35 year project was carried out to measure radial velocities of stars to help determine the structure of the galaxy.  In the 1960’s, Tom Bolton studied bright stars at the same time that satellites were observing. For one such star, Cygnus X-1, Bolton found a luminous star and radial velocities.  The star was orbiting a 3 solar-mass invisible star showing definitive evidence for the existence of black holes.   Observations using photoelectric photometry were begun in 1947.  J.D. Fernie used the 19 inch telescope in the south dome to study Cepheid variables finding that they could stop varying (i.e. Polaris).

Research at radio wavelengths started after WWII under Dan MacRae in the 1950’s.  The project was expanded and moved to Algonquin Park.  The study of galaxies began at the DDO in 1958 when Sydney Vanden Bergh used the Palomar Sky Survey to create a classification system of galaxies.  This was research using no telescope but the observatory’s own collection of the Palomar plates.

The department of Astronomy at U of T and graduate students were taught at the DDO until the 1960’s when this was moved to the physics building down town.  Parallel processing arrays connect the two sites. 

Helen Hogg used to travel to Arizona to get more photographic plates than she could in Ontario.  Then in 1970, Robert Garrison established the southern observatory (UTSO) with a 0.6 metre facility to study the southern sky.  Christine Clement used the UTSO to expand the work begun by Dr. Hogg on RR Lyrae variables but she eventually ran out of funding.  R. Garrison use the southern telescope to extend the system of stellar classification, and in 1987 Ian Shelton discovered the supernova 1987A. The UTSO closed in 2002 due to financial pressure.  

Ian then spoke about projects at the DDO. The telescope has been used every clear night for research.  Studies of radial velocities of short period binaries show evidence that there is a “silent partner’ in the cataclysmic variable.  Stars get close through some mechanism, usually by a third star that enables orbital velocities to be decreased.  An international  collaboration with the OGLE project is looking for the dark object in the gravity lens.  By observing radial velocities of galaxies and HII regions, we can see dark clouds between us and distant stars. The DDO can also “stare” at an object for 28 days – the only large telescope available to do this.  

On September 10, 2007, it came as a shock that the university would shut down the observatory even though useful projects have been done for the past 10 years.  U of T claimed that light pollution has made the telescope unsuitable for research.  Ian claimed, however, that his is not true.  Tom Bolton has for years lobbied for light pollution reduction and Richmond Hill has established a very strong light pollution bylaw.  As a result, light pollution has not made an impact since 1975. Last year, 19 papers were written in peer reviewed journals comparing very well with other 2 meter telescopes.  The DDO is being closed in fact because research interests in the Department of Astronomy have changed to large telescopes and there is money to be made from the sale of the DDO.

One possibility for the David Dunlop Observatory is to allow it to continue with its research but the problem is who will pay for this.   Alternatively, it can be preserved as a museum with heritage buildings or it can be used for outreach and as an education centre. The RASC  is helping with this last possibility.  So far there has been a rally, public talks, a blog on the Richmond Hill naturalist website, a petition and form letters to send, the “Observatory Park” initiative, and a petition to the provincial legislature. A grand child of David Dunlop has spoken out.  Ian pointed out the time frame for bids and decision for who will purchase the property. 

Finally, Randy Attwood spoke about the RASC initiative, meetings with the major and MPP, and raising money for the Observatory Park study.  

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