Watching YouTube videos and reading about space are, I think, wonderful ways to spend your time.  But actually observing the stars, planets, and galaxies of our celestial neighborhood with your own eyes? Pretty frickin' awesome!  So that's why I want to talk to you about telescopes.

If you take a look around, you might see some telescopes that promise to put space in your face at 500, maybe even 1000 times bigger than they appear to the naked eye.  Sounds great, right But before you take your relationship with space to a new level by getting a telescope, keep this in mind: when it comes to observing, bigger isn't always better.  The fact is, getting the best image isn't just about having the highest magnification.  The different functions of your telescope have to correspond to each other, or those high tech specs won't mean very much.

Telescopes have two main jobs: they make small things appear bigger and they make faint things look brighter.  Just how big things appear, their magnification, is determined by the combination of the main optics of the telescope and the eyepiece you're looking through. Telescopes all have a main optical component which is a lens or mirror. Either way, its job is to focus light at a distance known as the focal length. The focal length depends on what the lens or mirror is made of and how much it's curved. And the lens inside the eyepiece has its own focal length too. So you need to think about how those two pieces of optics will work together.

So for example, a lens with a focal length of 650 millimeters combined with an eyepiece with a focal length of 10 millimeters will give you a magnification of 650 over 10, or 65.  But still, magnification isn't everything, because not everything in the night sky is small. Some things that are hard to see are actually pretty huge, but also really faint.

Take the Andromeda Galaxy. If you had superhuman vision, it would look about 6 times wider than the full moon. But its light is spread out over such a huge area that we can barely see it. Since a telescope picks up more light than our eyes can by themselves, it lets us see things that have more diffuse light, like galaxies.

And the bigger the opening, or aperture, of your telescope, the more light it can pick up. So before you try to magnify things to just make them look huge, pay attention to the dimensions of the aperture of the telescope that you're using. The rule of thumb is that a telescope will pick up enough light for about 2 times magnification per millimeter of aperture. That means that if you have a telescope with a 100 millimeter aperture, you could reasonably see up to about 200 times magnification.

Finally, if you've done any backyard observing, you'll know that it's also pretty disappointing if you have a nice piece of equipment with great magnification and fantastic aperture, but then you find that the image is bouncing around so much that you can't tell if you're looking at Jupiter or smudge on your neighbor's window.

Even though it doesn't take a lot of math to find the right telescope, you also need a sturdy mount, like a tripod, that keeps your telescope securely pointed where you want it. A lightweight mount can cause your telescope to bounce around from the slightest touch, puff of wind, or even vibrations from the ground, especially if you try using it from the roof of a building. If you're looking to buy a telescope, do your research, a little bit of math, and you should be good to go.

Also, something we've been excited to learn about here at SciShow Space is that many public libraries and astronomy groups will lend out telescopes. So whether you're looking to buy and doing more research, or just want to borrow a telescope once a year for the Perseid meteor shower, you should have a lot of options.

And just remember that a crisp, clear, image will be more impressive than a blurry smear, even if it's small.  And that when it comes to observing the sky, bigger isn't always better.

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