David Rodger and his 10-inch Dob
Veteran stargazer David A. Rodger and his 10-inch GoTo Dobsonian reflector telescope.
GoTo Telescopes Reconsidered

How one experienced observer joined the GoTo-telescope brigade.

“To GoTo or not to GoTo; that is the question,” (with apologies to William Shakespeare.)

I still remember my shock some 10 years ago when I learned that a friend, who had shown no previous interest in astronomy, had purchased a small Maksutov telescope with a GoTo system. She didn’t know her way around the sky — I doubt whether she could have distinguished Orion from the Big Dipper. Yet by pressing a few buttons on the instrument’s hand control, she could be looking at, and tracking, the Andromeda Galaxy, the Double Cluster in Perseus or Saturn.

Notwithstanding my disdain, two years later I, too, had a GoTo telescope. What was it that changed my perspective?

David Rodger and his 10-inch Dob
GoTo convert David A. Rodger and his 10-inch computerized Dobsonian reflector telescope.

I learned my way around the sky on the Saskatchewan prairie. There, under ideal conditions, I could see the constellations in their entirety from horizon to horizon. Most of us today can’t do that. For one thing, light pollution is a huge and growing problem. Add tall buildings, mountains and trees to the mix, and our view of the sky is severely restricted. Urban-based star-hopping (the method by which we move from star to star in search of deep-sky treasures) is a frustrating challenge. From my present observing site in North Vancouver, I see only fragments of constellations, and more often than not, my target is obscured by some obstacle. I’m sure you recognize the experience.

There’s another factor that attracted me to a GoTo system. Our backs and necks can take only so much twisting and lifting. Astronomy seems to require quite a bit of both. Young necks and backs can tolerate a certain amount of this, but as we get older, bones and muscles tighten. When we force them into odd positions (such as when we’re peering through a finderscope aimed near the zenith), we are asking for trouble. GoTo systems solve these issues magnificently. And, unless the hunt is an essential part of your observing experience, automated pointing means you’ll spend a lot more time looking at stars, planets, nebulas and galaxies than looking for them.

There are two distinct families of GoTo systems: those with motors that automatically point to your desired target and more basic setups that require you to move the instrument. My Sky-Watcher 10-inch Newtonian reflector is on an altazimuth Dobsonian mount and employs the more sophisticated system, called SynScan by the telescope’s manufacturer. Once an object is selected, the computer in the hand control directs the mount’s motors to the correct location in the sky. From then on, the computer sends a constant stream of signals to the telescope’s motors and gears telling them just how much to move up or down, left or right, to compensate for the Earth’s rotation and its effect on the sky.

My Tele Vue NP127 and Orion EON 120mm apochromatic refractors also rest on GoTo-equipped altazimuth mounts. But there the similarity with my 10-inch Newtonian ends. With Tele Vue’s Sky Tour system, you do the work — there are no motors or gears involved. Once you’ve selected the object you want to view, the readout on the control box displays red-illuminated azimuth and altitude numbers it obtains from encoders located on the mount’s two axes. As you move the telescope, those numbers change. If you are pushing or pulling the telescope in the proper direction, the numbers diminish until they reach zero, signifying that your target should now be visible. Although it lacks some of the features of more sophisticated GoTo mounts, this “push to” system is quick and easy to set up and use.

A decade ago I’d all but given up observational astronomy, at least in the city. But thanks to my  GoTo telescopes, my interest in astronomy has been revived and I’m now seeing countless deep-sky objects that I would never have found using traditional search methods. My neck and back are grateful too.

David A. Rodger is an editor, a writer, broadcaster and an amateur astronomer living in North Vancouver, British Columbia. From 1967 to 1980, he served as the first director of Vancouver’s H.R. MacMillan Planetarium.

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