Q: How Do I Use My New Telescope? Pt 1-The Finderscope
Tuesday, December 26 2006 @ 11:59 pm EST
Contributed by: bobmoody
I previously gave some recommendations for buying a telescope in another AOAS website story. Then it occurred to me that a telescope is only as useful as how well its owner can understand how it operates. Just, “…point it up that-a-way!” isn’t a very good idea, although I more-or-less started this way myself. My earliest beginnings would have been more enjoyable if I’d had some helpful suggestions and explanations.
I assume, although it may not necessarily be correct, that every telescope owner wants to use their telescope to see something in the sky. That is, after all, the most widely accepted use for telescopes. So, here are a few (hopefully) helpful suggestions on how to make that new telescope live up to some of the promises you expect from it.
|STEP 1: Setup in daylight. Learn all the parts and functions of your telescope while you can see them clearly. In darkness, you'll be doing this all by touch alone.|
Oh, and BTW - this is my third attempt to pen a story about “How to Use Your New Telescope”, honestly! I’d get started and the words would just flow and flow…….endlessly……about too many things that you don’t need to know so early in the game. I'll touch on these things in Pt 2. So here is my third attempt, this time with a set of blinders on, so that I can keep this version below 20,000 words, I hope.
You’ve bought a new telescope, and you’ve just finished putting the last item together and attaching it to the telescope tube. This will usually be the finderscope since that’s generally the last step in the instruction manual. But what is seldom made plain in the instruction manual is that the finderscope is the most important thing you should learn about. Here’s why…..
All telescopes “see” a pretty small piece of sky. Almost every telescope’s widest possible field-of-view is only about the size of a quarter if you hold it out at arm’s length. That’s a pretty small field-of-view when you think about it, while the finderscope sees an area about the size of your clenched fist at arm's length. Now let’s abbreviate field-of-view to just FOV, and a big FOV is a popular misconception that most people have about what a telescope "sees". This may be one of your first realizations of many, many future new realizations concerning astronomy. Telescopes do NOT see large chunks of the sky!
|STEP 2: Locate a distant target.|
FOV is different from one telescope to another, but by only a very small amount. What you must understand here is that a telescope’s finder sees a several-times-larger FOV than the main telescope, making it easier to get the telescope pointed in the right area. Learning how to properly setup a finder will assist you in finding almost any target you seek and usually on the very first try. We begin our setup in daytime, outside, with a target at least 500 feet away.
“See That Telephone Pole Down the Road?”
First, a word about eyepieces. An eyepiece is what couples the light from an object to your eye, something similar to the way a speaker couples your favorite music to your ears. Great speakers can make a so-so receiver sound GREAT, and the same is true of good quality eyepieces for so-so telescopes. If your telescope came with low quality eyepieces, consider upgrading to quality eyepieces. It's a cheap way to dramatically improve your image quality in even the cheapest department store telescopes. Eyepieces can help a telescope see a wider FOV, and the eyepiece(s) that were supplied with your telescope are what you’ll start with. The lowest power, or more accurately the lowest magnification gives the widest FOV in your telescope. This is always the eyepiece with the highest number stamped on its side, maybe something like 25mm or 32mm.
|STEP 3: Center something you can see easily, like this insulator on top of that telephone pole.|
Click read more for the rest of this finderscope alignment article.
Use your lowest power eyepiece (whatever its number) to align the telescope with the finderscope. Eventually a one step higher power can be used after this initial process is better understood for a slightly better alignment. ALSO important, is the fact that everything seen through a telescope is UP-SIDE-DOWN. (Notice images) It doesn't matter if the object is inverted when you look at the moon or planets or galaxies someday. But in day time, it takes a little getting used to.
Devices are made as accessories called "image-erectors" which will show day time targets right-side-up for about $50 if it bothers you too much.
|STEP 4: Eyepieces...Use the LOWEST power, which will have the HIGHEST number on the barrel, something like 25mm. |
Now, locate a tree, or a telephone pole, or a water tower, anything that's at least 500 feet away and can be seen clearly. I always try to find a telephone pole’s uppermost point where there is usually an insulator holding the wire with its high-voltage current. You can use anything that is easily seen in the finderscope for your target, such as a fork in a tree limb, or a transformer on a pole, or a letter written on a water tower or billboard, whatever you like.
Point the telescope at the target you’ve chosen and focus the low-power eyepiece on it. You’re going to be adjusting the finderscope to point at EXACTLY the same point that's in the center of the telescope eyepiece. It may take more than one attempt so don’t get too frustrated if this task gets a little bit tedious.
Remember that the best way to find anything you want to see is to have the finder aligned precisely with the telescope. It’s something that nearly every amateur astronomer does every time they first set up to observe. That should give you some idea of how important this process is, since even the most seasoned amateurs do it every time they observe. Learn to do it again and again, over and over, each time trying to get it more precise than the time before.
|STEP 5: Put those finderscope crosshairs EXACTLY on the target, in this case, the insulator. Adjust the screws on the finderscope until it's centered, no matter how long, or how many attempts it takes, it's good practice!|
And this is where I’ll stop for this follow-up article. Doing this finderscope alignment, and doing it in daylight is the best way to learn more about how everything works on your telescope, too.
Don’t pass up a chance to use your telescope to view other targets in daylight, such as birds or other wildlife, too. You’ll be continually surprised at how much detail you’ll see through your telescope. Experiment with any other eyepieces you have to get higher and higher powers of magnification. Every time you use your telescope, you’ll pick up a little more valuable experience that will help you later on when you start trying to locate the moon, or Jupiter and his four Galilean satellites, or Saturn and her glorious rings! Eventually, you should be able to locate even the smallest and dimmest galaxy with ease, and you may even think back to this little article again that urged you to take it easy, and take it slow. You’re starting towards an understanding of how the telescope, finder, eyepieces and other components of a telescope work as one to give you the view of a lifetime, and it will soon become second-nature to align that finderscope.
When that memory of this article finally does creep into your mind, you may even be glad you followed my suggestions. Practice, practice, practice, every day if possible. And if the moon is out that evening, then zero in on it with your newfound skills and prepare for the first of many future involuntary gasps from yourself. It's going to get a lot more fun now that you can find what you're aiming the telescope at.