Monday, August 9, 2010

How to See Through Your Telescope

When I take my telescope to star parties, to show off the sky to the public, I get two types of people at the scope. One type of attendee approaches the scope, darts their eye toward the eyepiece, then is away again almost immediately.

"Did you see it?" I'll ask.

"Yeah, I saw it," they'll say as they buzz away, as if they're in a hurry to get somewhere.

Yet they'll have been at the eyepiece so briefly that they'll not really have even had a chance for their eye to focus properly. They've glanced at the image like a quick glance at a picture in a book. They saw the light, but not the object itself. They didn't give themselves a chance to see whatever it was I had in the scope, its shape, color, or any detail. Even when I know what I'm looking at, I can't really see it that fast.

The second type of viewer takes their time. They allow their eye to adapt to the view through the scope. Looking at an image in a telescope is not like looking at a TV screen, or a book, or at something that we see without any assistance in front of our eyes. It takes a moment for our eyes to adapt. The second type of viewer gives their eye a chance to adapt to the view.

They actually get to see what's in the scope.

When the object I'm presenting has fine detail to it, I make suggestions to the viewers who are willing to take the time to really look. I ask them if they can see some specific detail, to give them an objective. "Can you see the light yellow bands on Saturn?" "Can you see the dim star just below the brighter star? It's hard to see in the glare of the brighter star." "Can you see the dark area just below the bright nucleus?" And so on. Then I tell them to take their time to allow their eye to relax, since a relaxed eye is more sensitive to detail.

Learning to See All Over Again

When you're learning to use a new telescope, really taking time to learn to see is important to getting the most out of your scope. A lot of it is simple experience, coming from looking at many different objects and types of objects. Part of it is using good practices, giving yourself a chance to get better at it. With time, you'll find that you learn to see more of what you look at. You'll see more detail, and see more of what distinguishes one object from another. The galaxies won't all just look like "gray fuzzies" any more. You'll be able to make out the weather patterns on planets, and so on.

The Downside

The downside to this is that you may find that you notice flaws with your telescope that you didn't notice before. There are some instruments that this may never happen with, the fine ones at the top of the market, for example. But even some of these will show imperfections if they're of a sort that need adjustments to the optical train, like a Newtonian reflector.

Many telescope flaws are easily fixable. But with some telescopes the limitations may be something you can't overcome. In some cases, you may simply find that the scope, while fine for some types of observing, no longer fits your preferences for the type of observing you do.

Remember how I've recommended not to bet everything on your first telescope? This is why. No matter how good your first telescope is, it may not end up fitting your preferences that develop as your observing experience grows. Also, a scope that looks optically perfect to an untrained eye may look very different to a more experienced eye later on.

So be prepared to have your taste in telescopes change. Don't worry, it's a good thing.

Give Your Eye A Chance

Here are some practical things to do to allow yourself to get better views through your scope:

  • Allow yourself to look long enough at each object.
  • Make it so that you can relax while you observe.
  • Read other observer's reports, so you have specific details to look for.
  • Try observing the same object under different conditions, either by using filters or different magnifications during one session, or on different observing sessions at different times of year or under differnt sky conditions.
  • Observe reasonably often, if possible. You "forget" if you go too long between observing sessions. If you can do a number of sessions over a short period of a few weeks, then go without for a while, you'll get more than from the same number of sessions spaced out widely in time.
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