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How to Use Telescopes : Using Newtonian Telescopes


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.

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