Jasper Dark Sky Festival

GoTo Telescopes Reconsidered

How one experienced observer joined the GoTo-telescope brigade.

David Rodger and his 10-inch Dob

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

“To GoTo or not to GoTo; that is the question.” (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?

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.

Categories: Telescopes and Accessories
2 comments on “GoTo Telescopes Reconsidered
  1. I now own the same kind of instrument, also a 10″, despite having been an ardent defender of the “GoTo-is-bad” point of view for years. Going public made me switch (more about that in a second), but I fully agree with all the reasons David points out here. Yes, it’s hard to star-hop under light-polluted skies. And no, I don’t want to twist my neck any more!

    Going public, as I said, was the main reason. We were doing sidewalk astronomy, and I had an 8″ Celestron SCT with only RA drive and no form of GoTo (as well as a non-GoTo 80-mm ƒ/5 refractor, but that’s another story). Just pointing the Moon was a chore! I had to fiddle with the declination adjustment, make sure the polar alignment was good, etc. People had to wait. And since we often did it in sub-0°C temperatures (we’re in Canada, after all! [Montreal]), people did not WANT to wait, and they would go to another telescope. Then I decided I had enough, and got the GoTo. People are now looking, not waiting!

    When I use it alone, I do use the GoTo as it allows me to see more targets in less time, but I also use SkySafari on my iPhone (and soon on an iPad Mini or iPad 2 after the holidays) as well as a SkyFi wireless interface, so I can control the SynScan telescope with my iPhone… My favorite thing to do then is just to wander around the sky, often near a better-known object, and just look for “faint fuzzies” that I never even heard about before. It’s “only” a 10″ telescope, so I certainly don’t see as well as with the HST, but I still find my targets, and that’s a real joy… that I never even dreamed of with previous instruments…

    There is certainly something to be said for GoTo mounts!

    Before I finish… My sister-in-law got a GoTo NexStar 6 for her daughter’s 12th birthday. She asked me for advice before getting it, and I had a non-GoTo 90-mm Maksutov I could have given her, but we all agreed that it would not be a good first instrument for a young girl. With the GoTo, she found her targets in no time, and enjoys astronomy!

  2. Nick says:

    I always liked the idea of GOTO telescopes and been in support of them since day 1. It actually took 12+ years to make some of my fellow “brilliant” and “gifted” amature astronomers to make that realization. Technology is never a bad thing, it’s how you use it.
    I now have seen so many make the conversion over.

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