On Saturday, January 25, 2014, braving the bitter cold, the Royal Astronomical Society of Canada (RASC) hosted a members’ night for all the members at the David Dunlap Observatory (DDO). At these events, the members get together, socialize, listen to the planned lectures based on the theme of the event, and, if conditions permit, then observe the night sky. These events are hosted every month on Saturday evenings. This month’s theme was “Our Galactic Neighbours”.
I arrived at around 6:00 pm. Once I came in and found the gathering place, I met the members who were present. From the moment I arrived, until the time when the lecture started, I socialized with many of the members present. It was great to meet with a very diverse group of astronomers, teachers, academics, and other members.
At 7:30 pm, the lectures began in the presentation room. As per the theme of this member’s night, all the lectures were about galaxies.The first lecture that was presented to us gave a general overview of what a galaxy is, what we know about them in the past and now, their shape, and composition, satellite galaxies and other cosmological phenomena, such as black holes, dark matter, and dark energy. The second lecture given to us talked about distances with respect to galaxies. For example, We looked at the distances to our immediate neighbours. The Milky Way is 100,000 lightyears (lyrs) across, and M31 (Andromeda Galaxy) is 2.58 million lyrs away. Eventually, we start to expand our horizons and look further out seeing many galaxies clustered together, such as the Virgo supercluster, and when we expand our horizons further at a distance of 400 Mlyrs (Mega-lyrs) across, we see voids in the clusters 100 Mlyrs across. It was very intriguing.
Our final lecture talked about how we can observe deep sky objects ourselves. He gave us tip and tricks to help us identify what we see, how we can best see deep sky objects from Earth with proper positioning of our telescope and our eyes, and the obstacles we will face when observing deep sky objects.
After the lectures, the evening concluded. However, one of the members, who happened to be the chair of the DDO offered to give the members a tour of the main telescope used in most observations. Most members, including me, took advantage of that opportunity.
The telescope became operational on May 31, 1935, and was the second-largest telescope operating in the world at that time. This telescope was used by many renown astronomers throughout the years to study deep space objects. In 1971, most notably, the DDO was able to confirm that the Cygnus x-1 binary system has a black hole. In 2007, the University of Toronto intended to close the telescope down. However, in 2009, RASC put forward a proposal to run the telescope for educational purposes. As a result, in July 2009, it was reopened for public use by RASC and has since remained like that.
In the observatory, we saw the giant telescope that was used to observe the stars. It has a Schmidt-Cassegrain design, with a primary mirror concentrating the light to a secondary mirror and then reflecting it to the instrumentation.
Telescope used at DDO.
Secondary Mirror of Telescope.
Every time the telescope operators want to use the telescope they need to manually remove the covers of the mirrors.
The chair showed us how its mount works. It is an equatorial mount that follows the Celestial Equatorial Coordinate System, which slews the telescope based on Right Ascension (RA) and Declination (Dec) coordinates. (Think of it like Latitude and Longitude of the stars) Believe it or not, the mount is not computerized, and relies on a manual switch, and it also includes a hand crank for turning the telescope on its RA axis. It’s quite fascinating.
In addition, he showed us the spectrometer used in the telescope as well as the telescope very large 100 mm eyepiece. It gives the telescope 330x magnification, which is pretty good. It was quite a sight.
We then saw the electrical system of the telescope. It is quite old, since it still uses DC currents. One notable feature of the electrical system is a light bulb. It is notable because it is used to prevent the electrical system from freezing in these frigid Canadian temperatures. It is also worth nothing that the light bulb is still active after 60 years of use. It’s very intriguing. In addition, we learn that the dome rotation was powered not by gears but by a pulley system balanced with 10 stones (140 lbs) of weight. I say 10 stones because the weights were made in the UK.
In the other side, we saw the equipment used to recoat the primary mirror. Every two years, the aluminum coating on the mirror is recoated to maintain its reflective properties. The process they use is the same process used when it became operational. First, the operators use a manual elevator to bring the two ton mirror to the ground level. Before that, the bottom of the elevator needed an additional two tons attached to balanced the elevator. Once the mirror is at ground level, they use sodium hydroxide to clean the aluminum off, using diapers to wipe it down. It was quite astonishing.
Once the mirror is completely clean, they put the mirror in a vacuum chamber. Attached in the upper rim of the chamber are evenly-spaced diodes. Each diode requires three slivers of aluminum on it to coat the mirror. Once the aluminum is in, and the mirror is in place, they vacuum seal the chamber. In a specific sequence, they activate each diode which evaporates the aluminum and evenly applies the aluminum across the entire mirror. Once it has dried for a day, they take the mirror and place it back into the telescope. The secondary mirror goes through a similar process inside a smaller vacuum chamber.
Fun Fact: The primary mirror was so big that they had to bring it inside using an unfinished opening in the wall. It would not fit through the doors.
After that, our tour ended and we all went back home.
Overall, the event was a great success. I learned a lot of new interesting and informative facts about the universe around me. Closer to home, I learned the history of the DDO, how the DDO’s main telescope works, and what it takes to maintain it over the years.
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