How does telescopes work? And types of telescopes

Looking for a Telescope? Which Telescope should you get? Well, let's look at the different types of telescopes in this article.

TYPES-

• Refractor Telescopes
• Reflector Telescopes 
• Compound Telescopes

Now before getting to them, let's see some of the points that you gotta look for in a telescope, being Aperture, Focal length, focal ratio, and magnification 

APERTURE - 

• Being the most important specification to look for in a telescope. It is the amount of light the telescope can capture, or the day the light gathering ability will determine how sharp and bright the image would be.
• For beginners aperture ranging from 70mm (2.7 inches) to  254mm (10 inches) is enough, the larger the aperture the better the image will appear, for say a 10 inches aperture telescope can take up to 13 times more than 70 mm (2.8 inches) telescope, another example would be than the eye have an aperture of 7mm (0.28 inches), so a telescope with 70mm (2.8 inches) will gather 100 times more light than the eye, so a much clearer and detailed image will be obtained.

• Aperture is determined by the size of the primary lens or mirror, well depends on the type of telescope, more on that later.
• So should you get the biggest aperture telescope that is on the market, well but then the telescope will be very bulky and heavy, and also a critical hit on your pocket.

FOCAL LENGTH -

• 
  It is the distance where the image is formed from the lens or mirror, at focus, focal length determines the ability of the telescope to magnify, now ow much a telescope is able to magnify is determined by the focal length of the telescope and focal length of the eyepiece, the smaller the focal length of the eyepiece the more the magnificence of the telescope, as magnificence can just simply be calculated by diving the focal length of the scope by the focal length of the eyepiece.
• Say a telescope with a focal length of 1000mm, and an eyepiece of 20mm
• M = Focal length of scope / focal length of the eyepiece.
• M = 1000/20
• M = 50
• So you will be able to an image magnified up to 50 times.
• Now getting a telescope with the greatest magnification isn't always viable as due to some limiting factors, some being aperture, atmospheric conditions, and others.
  
  
  
  

FOCAL RATIO -

• The focal ratio denotes the relation between focal length and aperture of the telescope, it can be obtained by simply just diving the focal length by the aperture, and the focal ratio is written as f/. Usually ranging from f/4 to f/14.
• Now is the focal ratio is on the low end, say f/4 or so, so it will not magnify as much but the field of view will be more and will also give a detailed image, and a telescope with a higher focal ratio, say f/10 will provide a much magnifies image for their aperture and are good for looking at planets and such.

MAGNIFICATION -

• Now as said before magnification will depend on the focal length of the telescope and eyepiece, so choosing an ideal eyepiece is also optimal, with higher magnification, the details will be lost, so choosing the right telescope for the job will be optimal.
• Now you should not push magnification that much depending on the aperture, like a telescope with a certain aperture can do so much to magnify and keep the image detailed and clear, so it's better to not take a telescope with a low aperture and high magnification, it will be a blurry mess, as an advice a telescope's top magnificence with which you can obtain a good image is twice its aperture in millimeter or 50 times in inches. Any higher than that, the quality of the image will take a deep dive into the abyss.

TYPES OF TELESCOPES

REFRACTOR TELESCOPE -

A refractor telescope say is how a usual telescope can be found with a long tube and a large lens in front.

These work on the principle of refraction, as the name suggests, they use lenses, the light enters through the big convex lens in the front, which bends the light inwards, and makes the image smaller as the image is focused, and then the light travels through the eyepiece convex lens from where the light enters our eye.

As the image is focused, it is brighter, clearer, and magnified, it makes the object look much closer.

These types of telescopes are much more stubborn and require very little Maintainance, and are quite easy to set up.

Most telescopes will aperture less than 80m is usually refractor.

ADVANTAGES -

• They can give a much detailed, brighter, and sharp image per inch of aperture than any other type of telescope, as the lens is more efficient than the mirrors, and also in other telescopes, the secondary mirror obstructs some of the incoming light, why, well we will get to that later.
• The lens is very rugged so these telescopes are less likely to be misaligned, which makes them stubborn and require little to no maintenance, making them an on-the-go instrument for some astronomical photography or star gazing.
• They provide better colour contrast.

DISADVANTAGES -

• They can be more expensive per inch aperture as the bigger lenses are more expensive to produce than mirrors.
  
  
  

REFLECTOR TELESCOPE -

These use mirrors to gather light and focus it, this design is most common in the Newtonian reflector, they have a primary concave-shaped mirror at the bottom of the telescope, from where the light is reflected to a mirror which is placed diagonally, to reflect the incoming light from the primary mirror to the eyepiece.

ADVANTAGES -

• They will give a higher aperture for the price you want, and when well maintained will give a sharp and contrasty image at a cheaper cost than a refractor of the same aperture.
• They work best at focal ratios of f/4 to f/8, allowing them to have a wider field of view relative to their aperture.
• These can be used with low tripods and Dobsonian mounts with easy-to-use pivots.
• They offer brighter and detailed images for each buck.

DISADVANTAGES -

• They need to be maintained quite frequently, as the mirrors need periodic alignment to be done.
  
  
  

COMPOUND TELESCOPE -

Compound telescopes or Catadioptric telescopes use a mix of both worlds, refraction, and reflection can say they are a hybrid of refractor telescopes and reflector telescopes. A primary concave mirror which gathers the light which reflects light a secondary mirror which then reflects light through a hole in the primary mirror into the lens at the back of the telescope, which lets it have a focal length quite greater compare to the length of the tube.

ADVANTAGES -

• These are quite compact and light.
• They can obtain a larger aperture, long focus telescopes while being compact
• They can have focal ratios quite larger, say f/14, allowing for having a high. magnified and detailed image.

DISADVANTAGES - 

• As with the Reflector telescopes, maintenance is also necessary for these, to re-align and stuff.
• Unable to obtain wide, a lower field of view.
  
  
  

OTHER THINGS TO LOOK FOR

• Mounts - Making the telescope stable and follow a celestial object. There are a few types of mounts. 
• Alt-az mounts (Altitude-azimuth), working like pan-and-tilt tripods, good for small telescopes. They are more simplistic and compact.
  
  
• Dobsonian mounts, place the pan-tilt head on the ground, these are very sturdy, letting you glide across the two-axis smoothly. 
  
  
  
• Equatorial mounts, these are alt-az mounts but the azimuth axis is parallel to Earth's spin axis.
  
  
  
• Finders - A miniature telescope which is mounted on the main telescope, which has a crosshair, you can view the sky through these to center the object you are following and getting it on the main telescope's view, you can say these are to aim the main telescope, like gunsights.
  
  
  

WELL, WHAT TELESCOPES ARE USED IN SCIENTIFIC STUDIES OF VERY DISTANT OBJECTS?

Well, they use radio telescopes, these telescopes don't gather visible light, these gather weak radio waves coming from outer space, bringing it to focus, amplifying it, these are used to study radio waves coming from stars, galaxies.

These are able to capture radio waves ranging from 1 mm to 10 meters. 

These are much better than optical telescopes as these can be used in any weather condition as radio waves are not obstructed by clouds, and these lets us study the universe, and analyze the data, and we are able to calculate many things from that day, like the compounds making up distant planets, stars, and finding new exoplanets and many more.

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