The Urban Astronomer

Geoff Gaherty
Toronto Centre RASC


Most of the books on amateur astronomy hold out the holy grail of the perfect dark sky site. Although I treasure the few nights in the year I can be out under a truly dark sky, I also realize I make about 95% of my observations from my back yard in downtown Toronto. There’s an old adage that says that the best scope for you is the one you use most often. I'm gradually coming around to the realization that the best observing site is also the one you use most often, and for me that’s my urban back yard. This is leading to a change in my observing priorities, with deep sky objects taking a back seat to the Moon, planets, and double stars.

Let me describe my observing situation. I live in a big old house a few blocks southwest of Yonge and Eglinton, a major intersection close to downtown Toronto. I did have some input into the choice, so I tried to get a house with a large back yard and reasonably wide views of the sky. My house faces west onto a north-south street, so the best observing location on my property is in the northeast corner of my yard, as far from the street and the house as possible, and with a view to the south mainly over lawns and trees. My house blocks a large part of the western sky, and surrounding trees take out parts of my horizon in most directions except to the southeast. All in all I’d say that about 75% of the sky is visible to me from this one location.

Because my yard is quite large, I also have the option of setting up in locations other than the northeast corner. This probably gives me another 10% of the sky. In winter when the snow is deep in my yard, I often observe from my driveway, which has terrible horizons (trees and houses on all four sides) but which works well for objects close to the zenith, such as the winter Moon and planets, as well as protecting me from any wind. There’s also a narrow observing window down my driveway between my house and my neighbour’s which lets me follow the planets down towards the western horizon somewhat. In a pinch, when something important is happening in the western sky, I have observed from my front yard, but streetlights make this area extremely bright.

Local light pollution is fairly minor since a tall cedar hedge surrounds much of my back yard. The only ongoing problem is one of my neighbours to the southeast who persists in turning on his pool lights at all hours of the night and all nights of the year. These shine somewhat onto his pool, but mostly straight into my back yard. Beyond my immediate vicinity, I have the sort of sky you’d expect from my urban location. Most of the time the limiting magnitude is about 3.0; on cool mornings after a front has passed through, I can sometimes reach magnitude 4.0.

Because of the limiting magnitude of my back yard, some popular observing targets, notably anything beyond the brightest deep sky objects, are pretty much impossible. However there is quite a wide range of objects which are available, more than I can possibly cover. Here I’ll summarize the sorts of observing projects I carry out regularly from my back yard. I’m using the word "projects" loosely to include some serious astronomical research but also things I do just for fun.

The solar system: The Sun, Moon, and planets are visible in even the worst light pollution. Though temperature instability associated with big cities may cause localized seeing problems, much of the time I find the seeing from the northeast corner of my yard very good, as long as the objects are higher than about 30° altitude. This is because my neighbourhood is blessed with a large amount of foliage. Things are not as good when I’m restricted to my driveway in wintertime, since there are a number of chimneys arrayed around me. However, by having my telescope on dolly wheels, I can often move to a less disrupted sight line.

I recently bought a solar filter for my "grab-and-go" telescope, and leave it set up just inside my garage door, which faces south. On any clear day I can be looking at sunspots in seconds. My main lunar observations are "lunar tourism," crater-hopping down the terminator from one pole to the other with Rükl’s Atlas of the Moon in hand, looking for interesting rilles and crater chains. Sometime in the future I may resume the challenge of making pencil sketches of lunar formations, but for now I’m content just to watch.

With Mars this summer I tried to make a disk drawing on every possible opportunity. This worked well until the dust storm hit in early July, and I’ve not had much luck since. Back in my "first life" in astronomy, in the late ’50s and early ’60s, I devoted many hours each clear night to timing Jupiter’s cloud features as they crossed the planet’s central meridian. This requires no special equipment beyond a good telescope and a wristwatch, and is a pleasant way to spend a couple of hours. By such intimate study, my eye rapidly becomes very sensitive to fine details that escape casual viewers. Such transit observations have been the mainstay of the study of Jupiter’s atmospheric currents for over a century. This year I’ve started observing transits again with a vengeance. Whether my enthusiasm will hold up under the increasingly chilly nights remains to be seen! Although always achingly beautiful, Saturn is too static to attract my interest much. I do enjoy tracking its many bright moons and seeing which ones are visible in various telescopes.

Last year I faced a long withdrawal period when all the planets were close to the Sun. To give myself a new challenge, I started to observe the many asteroids listed in the RASC Observer’s Handbook, watching them move from night to night and sometimes from hour to hour. The starhopping skills learned while deep sky observing proved equally useful here.

Double stars: Beyond Epsilon Lyrae and Albireo, I’d never had much interest in double stars, until I bought a 10cm refractor a couple of years ago. Doubles which had never been terribly inspiring when masked by the various aberrations of my Newtonians suddenly became objects of great beauty in my small refractor. They were also just as pretty in my urban sky as they would be under a pristine dark sky. There is a seemingly endless variety of colour and brightness contrasts, such as the tiny companion lurking in Rigel’s brilliant glow, which I discovered quite by accident one night while looking for a bright star to use for a star test. While some observers use close doubles to challenge their scopes’ optics, I prefer to simply enjoy their beauty. I’m gradually working my way through the Astronomical League’s excellent list of 100 double stars.

Variable stars: In my forty-odd years as an amateur astronomer, I’ve sampled most of the avenues of visual observation open to me. The only exception has been variable star observing. I did join the AAVSO many years ago, and contributed observations for a month or two, but I just couldn’t get into it. Recently I read Leslie Peltier’s autobiography, Starlight Nights, and have begun to feel the tug of interest in observing variables...time will tell if I respond to this lure, but it is a fine example of serious research that can be practised as well from the city as from the country.

Deep sky objects: This is the hardest one to write about, because, like many amateurs, I’ve devoted much time and energy to deep sky observing over the years, being one of the first people in the world to observe all of Messier’s catalog as part of the Montréal Centre’s pioneering Messier Club, and subsequently re-observing them for my RASC Messier Certificate a few years ago. When I completed my RASC Finest NGC Certificate recently, I made a long list of new fainter DSOs to track down but, I must confess, I don’t have much heart for it. The last few Finest NGCs were really hard work in the bitter cold for my sixty-year-old body, and I paid a high price in arthritic pain. I once before managed to kill my love of astronomy for many years because I made it into work, and I was finding myself doing the same thing with the quest for ever fainter deep sky objects. So I think I’ll stick to being a connoisseur of the best and brightest deep sky objects, savouring them through my telescopes on the rare occasions when I get out under a dark sky, and not trying to struggle through yet another list of faint fuzzies.

Even in my back yard, I’m not denied views of some of the best DSOs. Open clusters and planetary nebulae show up really well even through light pollution, the latter with a little help from my narrow band filter. I can make out three or four diffuse nebulae and about a dozen galaxies, but that’s about it. So I do have a few goodies to show visitors, and of course I can always lose an hour or two in the depths of the Orion Nebula, which not even the worst light pollution seems to be able to destroy.

Telescope testing: One area I’ve become increasingly active in has been the testing of new telescopes, partly those supplied by a local dealer, partly those I’ve bought myself. I’ve learned the art of star testing, which doesn’t require dark skies, and I make much use of my intimate knowledge of the Moon and planets to push scopes to the limit in the resolution of low-contrast detail. I can even do some comparative testing on deep sky objects because of my knowledge of the characteristics of my "reference" telescopes.

Scopes for urban skies: I sometimes read that this or that telescope is more or less suitable for light-polluted skies. In practice, I find that is mostly a myth. I’ve used all types of scopes from my back yard, and my current favourites are an unlikely combination of a 15cm Intes Maksutov-Newtonian and a 25cm Meade Dobsonian.

The Mak-Newt is my most used scope by far, because it's relatively easy to set up and rewards me with superb views of the objects that work best in my back yard: the Moon, planets, and double stars. The Dob has an f/4.5 mirror, supposedly unsuitable for use under light polluted skies, yet I’ve found it to work quite well. It’s also often my "quick look" scope, since it can be up and running in less than a minute, being already cooled down in my unheated garage and carried out in two trips. What I've gradually realized is that I don't have much use for a huge field of view in the city. I find it more productive to use higher magnifications to darken down the sky background. I found that the Rigel QuikFinder that worked so well under dark skies was next to useless under the bright skies of the city, so I’ve reverted to an optical finder which allows me to see at least some stars to start starhopping from.

My most important realization has been that, because I’m observing from only a few steps from my back door, I’m out there just about every clear night, even if only for a few minutes. Far better than putting off my observing until I get to a dark sky site, and then watching new Moon after new Moon pass by enshrouded in clouds. I’m as active as an observer as I’ve ever been, and all because I’ve accepted my situation and adapted to being an urban astronomer!
 
 

© Geoff Gaherty 2002