Telescope Focal Length Explained

when you as a beginner start searching for a telescope to buy then you come across many different terms such as aperture focal length and focal ratio etc if you're unfamiliar with these terms you get more confused so today we will explain everything about a telescope's focal length the aperture is the most important parameter of a telescope focal length is a parameter that can greatly impact how the object looks and the quality of the image you'll see through the eyepiece knowing the importance of focal length can help you to make an educated decision while buying a new telescope or upgrading an old telescope usually a telescope works like this light is collected from the aperture of the telescope and it is transmitted to the focuser which is the part where the eyepiece goes so you can see the image formed the focal length is the distance between the entry point of light in the telescope and the exit point now you might be wondering focal length is just a distance between the entry and exit point of light so the focal length is just the length of the telescope tube this is true in the case of refractor telescopes in the old times they used to build long telescopes with longer focal lengths at the time lynn's crafters produced better products than mirror makers so most of the telescopes during that time were refractor type telescopes that's why the telescopes you see from older times have very long tubes ultimately giving you a higher magnification nowadays in modern telescopes we use a combination of mirrors and lenses so modern telescopes can be much more compact and still have higher focal lengths such as the schmidt casagrain type telescopes these telescopes are compact and have multiple mirrors inside where light is reflected from and then reaches the eyepiece ultimately extending the focal length for compact design telescopes so why is the focal length important if you know the focal length of a telescope then you can determine two important things about the telescope one is its magnification and the other is its field of view magnification means how much you can zoom in on an object when you zoom in on an object you can see more details of that object however it's not always the case as you magnify more you also magnify the noise around the image that's why you have the highest useful magnification of a telescope in the specifications this magnification limit is determined by the aperture of the telescope till this magnification point you can see the object clearly to calculate the magnification you can divide the focal length of the telescope by the focal length of an eyepiece from this formula you can see longer focal length means higher magnification the second factor is field of view field of view is how much area of a sky you can see through a telescope in degrees when you have a large focal length then the field of view of your telescope is small the smaller field of view is useful in looking for nearby objects such as planets or moons why is a small field of view good for viewing planets because you have a longer focal length and because of this you can zoom in on an object as much as you want to see the details of that object when you have a short focal length then the field of view of your telescope is wide a wide field of view is good for observing deep space objects where you need to see the large portion of the sky to see objects like galaxies or nebula can you change the focal length of the telescope usually the focal length of a telescope is fixed but if you use some extra accessories then you can increase or decrease the focal length of a telescope to increase the focal length of a telescope you can use the barlow lens or focal extender they come in different sizes such as 2x 3x etc to decrease the focal length of the telescope you can use the focal reducer they are simple and can be directly connected with the eyepiece if you're using a 0.5 x focal reducer then it will reduce the focal length of a 1 000 millimeter telescope to 500 millimeters so which focal length telescope should you buy it totally depends on you and what you want to observe if you want to observe planets then go for the longer focal length telescopes if you want to see deep space objects then go for the short focal length wide field of view telescopes for astrophotography the same rules also apply planets look great on longer focal lengths usually one thousand millimeters plus short focal lengths are better for deep sky objects usually from 600 millimeters to 1000 millimeters if you're a beginner then buy a telescope that has a focal length of at least 600 millimeters if you go below 600 millimeters then it might not give you a great viewing experience usually the telescopes below 600 millimeters focal length fall in the category which is suitable for kids we hope you understood everything about the focal length of the telescope and how they're useful for a telescope please visit our website to know more about 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Channel: Alien Tech

Views: 16,481

Keywords: focal length, lens focal length explained, telescope focal length explained, telescope focal length formula, telescope focal reducer, telescope focal length to see saturn, telescope focal length comparison, focal length explained, what is focal length, telescope focal length for astrophotography, focal length telescope, focal length telescope explained, focal lengths, telescope magnification formula, telescope magnification explained, calculate magnification

Id: Jw9b7CmAiA0

Length: 5min 30sec (330 seconds)

Published: Sat Jun 18 2022