Using Newtonian Telescopes

Video Transcript

"OKay, so this telescope, this particular telescope is called a Newtonian telescope because Isaac Newton invented the basic configuration. It has a mirror at the bottom, you can see the reflection of the mirror, and it has an eye piece, here. There are two mirrors in this, the mirror at the bottom and the secondary mirror which is right here. Now, what happens is, light comes in in parallel rays, hits the bottom mirror, and because the bottom mirror is curved, it causes the light to bounce forward and form a light cone. And then the secondary mirror is a flat mirror that's at a 45 degree angle, it sends the light out the side. And, if you were to use this telescope, you would point it at whatever object you wanted in the sky, and then you would look in the eye piece. Now, there's also another telescope on this, and all telescopes will have a finding telescope. This is a little refractor, it's a tiny telescope. And, it's very important when you set your telescope up for the first time, to have this little refractor, or whatever type of tinder you have, aligned with the optical axis of this telescope. They're very easy to align. You would want to set the telescope up and kind of get down the barrel and point it, point it towards a street light or some object that you can easily see, and center it in the main telescope. Bring it into focus and then look at the small telescope with the finding telescope and use your two little thumb screws, moving them independently, to align the object that your looking at through main telescope with this telescope. Because, if it's not, and you look in the sky, they're going to be pointing in different directions, it would be very hard to find. The reason you use a finding telescope is it gives you a very wide piece of the sky. Your primary instrument will give you a smaller piece of the sky, and it's much easier to find it with this. Now the other thing that you may want to start with is, use the eyepiece that is the longest focal length. This particular eyepiece says it's 25 millimeters. Well, this telescope also comes with a 12 millimeter eyepiece. I would want to use the 25 millimeter because that gives me the biggest field of view. And, when you start out, you want to use the lowest magnification as possible. A lot of the telescopes that you might buy would talk about 1000 power. Astronomers, amateur astronomers never use 1000 power, or very, very rarely. They use low powers because those give you the most beautiful fields in the sky. So, start out with your highest millimeter eyepiece. If it's a 40 use it, if it's a 25 use it. Stay away from your 12's, 10's, 6's until you have an object in centered in the telescope. Make sure you tighten the screws down well. You don't want to over tighten and strip them. But, make sure you tighten them so that the eyepiece doesn't slide out. Then the focusing mechanism. Bear in mind, everyone's eye is a little bit different. So, if you look at something, it may be in focus for you, and the next person that comes up, it may be out of focus so they'll have to focus select. This particular telescope is on a mount called a Dobsonian mount. It was invented by a man called John Dobson. It's the simplest type. I really refer, or like to recommend that this telescope be the first telescope that you buy if you haven't purchased one yet. Because, they're easy to set up. They're on a cradling base, almost like a Lazy Susan. You can move them in altitude and you can move them in asthma. You get out of your car, if you're out at a dark sky sight at night. Set it on the ground in a level place, set the cradle on the ground, put the telescope in there, you're ready to go. Whereas with the more complex telescopes, like the Smith cassegrains that are on tripods and you have to align it with the polar axis of the earth, that takes longer. So, these are really simple telescopes to move, to use. The main disadvantage is that, you will have to move it, it doesn't track the sky on it's own."