Telescope Buying Guide: Aperture

Video Transcript

"When selecting a telescope for astronomy, aperture is actually the most important feature, you want to consider. Now, aperture, is a fancy word for the light gathering ability of your telescope. How much light it can soak up, how big your lens or your mirror may be, in this case. The light gathering ability of the telescope, is important, because that's what makes those distant objects, seem a bit brighter, those dim fuzzies that we look for. You see further back in time, if you will, with a larger aperture telescope. The magnification that you'll get with your telescope, will also depend on the aperture here, but typically seeing conditions permit that we use right about a hundred magnifications, or so, kind of a sweet spot for astronomy, and I say that though, even though a big scope like this, is capable of much more magnification, than the little guy I've got right here. Typically, my seeing conditions outside don't allow me to do more than about, I'm going to say, a hundred and twenty, a hundred and fifty magnification, with any of the instruments that I have here, and one of the reasons is, that our location here in Anacortes, where it's sea level. We've got ten thousand feet of atmosphere to focus through, so as I increase the magnification, I'm increasing everything I'm looking through, as well. Plus the jet stream is above us, so no matter if I take out the bigger scopes, you've seen here earlier, or one of these little guys here. Maybe the eight or the ten. I'm going to say about one twenty magnification, is going to be about the high end, and I'll probably settle in right about eighty magnification, or so. As a rule of thumb, these telescopes, will give you fifty magnification per inch of aperture, but you really need ideal conditions, to do that kind of magnification. While these little guys here are ideal for lunar and planetary viewing, if you want to see deep sky objects, objects that are further out in our Milky Way Galaxy, or even beyond the galaxy, a Dobsonian such as this, of six inches of aperture or greater, is an ideal place to get started. You'll see Super Nova. You'll see globular clusters. The open clusters are beautiful through such a telescope, and you really need at least six inches, I feel, to start bringing in the deep sky objects. We'll qualify that a little bit later, by talking about your seeing conditions, and what kind of area you view in, but typically, a six inch Dobsonian, eight inch Dobsonian, very cost effective, and very good for pulling in deep sky objects, and still portable, and easy to take in and out, as well."