How to choose your first telescope

[Music] [Music] [Music] hello and welcome to another episode of the scart knight magazine vodcast this month in the run-up to Christmas we thought it'd be a good idea to give you some advice if you're thinking about buying your first telescope so here's our video guide to what you need to look out for when you're buying your first coat so there are three main types of telescope there are the reflectors the refractors and what are known as the catadioptric telescopes or compound telescopes now the reflectors basically use a polished mirror to collect light from celestial objects and focus it at the eyepiece where the image is formed refractors use a lens to do the same thing whilst catadioptric telescopes basically use a mixture of lenses and mirrors to produce the image that we see when we look through the eyepiece now within these types are lots of different tasks of designs so with the reflectors for example there are Newtonian reflectors which is essentially a long cylindrical tube with a main mirror at one end and a little eyepiece holder coming off the side at the very top there's also in the reflector category the Dobsonian telescope which is essentially a Newtonian reflector but on a very simple swiveling mount you know the front here we actually have a 66 millimeter refractor and here we have a quite large hundred and 52 millimeter maksakov Cassegrain which is a type of catadioptric telescope well if you want to look at fainter objects things like galaxies and nebulae you'll probably want a reflecting telescope and I'd actually say that Dobsonian telescopes are pretty good for this because you can get quite a large mirror for the amount of money that you pay if you want something that's a little bit more portable than a maksakov Cassegrain might be for you if you want a good all-round beginners telescope then try something like a 4 to 6 inch Newtonian reflector that'll show you things like the planets the bright and their beliefs certainly the moon surface the craters and the mountains and the Seas as well as some of the more interesting clusters and double stars well the main specification you want to look for when buying a telescope is not the magnification you'll often see people saying this has hundreds of times magnification that's not what you want to be looking for you actually want to look for the aperture that is essentially the size of the main lens or mirror so in the case of this Maxo top it will be the size of the mirror at the back here and in the case of this refractor down here that would be the size of the main front lens so the aperture is really important because the bigger the main mirror or the bigger the main lens the more light the telescope can gather that means that if you're looking at a faint galaxy you can collect more photons of light and the image that the eyepiece will be brighter so magnification is essentially the number of times a telescope enlarges the naked eye view of an object so it could be the moon or Jupiter say now you work out the magnification by knowing two things about the equipment you use it you need to know one the focal length of the telescope you're using as well as the focal length of the eyepiece you're using and you can find the focal length of the eyepiece because it's usually inscribed on all the eyepieces in this case this one's a 30 millimeter eyepiece this one here this one is a 13 millimeter eyepiece and the way you work out the magnification is simply you divide the telescopes focal length by the focal length of the eyepiece so if you are using a 2,000 millimeter focal length telescope and you're using a 20 millimeter eyepiece in the eyepiece holder you'd have a magnification of a hundred times so you can see from the way we calculate the magnification of a telescope that changing the eyepieces with different focal lengths will change the magnification so if you're using a much shorter focal length eyepiece like this 10 millimeter here you get a much more magnified view with this one then you will with a 30 millimeter eyepiece like this one but you don't want to over magnify when you're using your telescope it's a common misconception that you should really push up the magnification and try and get as much of it as possible you don't actually want to do that you want to magnify as much as your telescope and the conditions alive remember if you're magnifying too much you're also magnifying all the defects with the view so if the atmosphere is undulating you're actually magnifying those undulation and you create a worse image than if you just held back that magnification and use the lower value you will get a better image your first telescope will probably come with one or two eyepieces and it's a good idea to have a small range of eyepieces so that you can get different magnifications now if you're looking at fainter wider objects something like a galaxy like m31 the Andromeda galaxy you don't want to have a lot of magnification what you actually want is a wider field of view which is what you get if you're using a longer focal length eyepiece if however you want to look at a planet say Jupiter at the moment or the moon's surface to look at some craters you want a shorter focal length eyepiece so something like this 10 millimeter eyepiece would be ideal in that case so there are two main types of telescope 9 you have your altazimuth mount and your equatorial mount now our tazza mount to the simplest type of mount they simply move around and around horizontally which is known as azimuth moving in azimuth and up-and-down which is moving in altitude and they can move between 0 degrees altitude which is at the horizon and 90 degrees altitude which is straight above you a point known as a zenith now a simple photographic tripod like this one could be considered an hour TASM of mount as it does exactly the same thing it moves around and around in azimuth and up and down and that's a very easy way of mounting a telescope you can put it on a photographic tripod or a simple art azimuth man and that'll be great for moving around the sky and looking at it things but probably not good for tracking them and that's where the equatorial mount comes in that's essentially amount that's aligns a telescope to the rotation axis of the earth so that it only needs to move in one axis to follow a star the mount is one of the most important parts of the telescope because if you don't have a sturdy solid mount the telescope's are going to wobble all over the place so when you're looking at your telescope one thing you really need to do is check that the mount is solid you don't want any plastic flimsy parts that are going to move around you want something that's going to be rigid for the telescope to sit on top of very safely and securely well go to telescopes are actually really popular nowadays what you need to do to use a go-to telescope is align into the night sky so it knows where it's pointing and then you can use the little computer in the onboard handset to navigate to thousands of different objects so this is great if you want to quickly whizz across the sky looking at lots of different objects but if you want to slowly learn the night sky and learn how to use the telescope a go-to telescope is perhaps not the best thing to start off with in that case you probably just want a manual telescope without any of the bells and whistles well if you're not ready to get a telescope why not get a pair of binoculars a good pair like these might cost around about 25 pounds and you can see all sorts of things through them you can see star clusters some of the bright and nebulae and galaxies and they'll also show you Jupiter's moons and some of the craters on our own moon well that's it for this episode of the Scott night magazine vodcast we hope now that you get a better idea of what to look for when you're buying your first telescope if you're interested in learning more about getting started in stargazing then on our cover disk each month we have these print out and keep guides to learning astronomy in 10 easy steps and buying your first telescope so there's lots of information there but meanwhile for me that's all clear skies and I'll see you next month [Music] [Music] [Music]

Channel: BBC Sky at Night Magazine

Views: 146,889

Rating: 4.8771696 out of 5

Keywords: telescopes, reflector, refractor, lens, mirror, magnification, astronomy, stars, planets, galaxy, nebulae, Dobsonian, Newtonian, eyepieces, aperture, equatorial, altazimuth

Id: i6rXWIVgjVQ

Length: 8min 54sec (534 seconds)

Published: Tue Nov 30 2010