If you are interested in space science and exploring the galaxy, it is essential to get a telescope but how does it work? What can it see? How does the telescope magnification work? Having taken a keen interest in space, I have written this blog to answer all the questions you might have about telescopes.
What is a telescope?
A telescope is an instrument that allows us to see far-away objects by using a combination of lenses and mirrors. They were invented in the early 1608s by Hans Lippershey, a Dutch eyeglass maker who submitted his first patent for a 3x magnifying telescope. This first telescope had a concave eyepiece aligned with a convex objective lens. The convex lens was used to gather light from distant objects, and the concave eyepiece worked like a magnifying glass to make those objects appear larger.
Table of Contents
Types of Telescopes:
There are three types of telescopes: reflectors, catadioptric, and refractors.
Reflector telescopes:
Reflector telescopes use mirrors to gather light from distant objects and then focus that light onto an eyepiece, which magnifies the images. The most famous reflector telescope is the Hubble Space Telescope, which was launched into orbit in 1990.
Hubble primary mirror is 2.4 meters (7.9 feet) across, and its secondary mirror is just 0.6 meter (2 feet) across.
Refractor telescopes:
Refractor telescopes use lenses to gather light from distant objects and then focus that light onto an eyepiece. The earliest refracting telescope was built in 1608 by Hans Lippershey, who is often credited with inventing the telescope. However, it is important to note that many other scientists were working on similar devices at around the same time.
The first refracting telescope had a convex objective lens and a concave eyepiece. This design was later improved upon by Johannes Kepler, who added a second convex lens (the field lens) between the objective lens and the eyepiece. This double-lens design is known as a Keplerian telescope.
Catadioptric Telescopes:
Catadioptric telescopes are a type of reflector telescope that uses both mirrors and lenses to gather and focus light. The most common design is known as the Schmidt-Cassegrain telescope, which was invented in the 1930s.
This type of telescope is often used for astrophotography because it can be made relatively compact while still gathering a lot of light.
How do telescopes work?
Telescopes work by using a combination of lenses and mirrors to gather light from distant objects and then focus that light onto an eyepiece, which magnifies the images. The type of telescope you use will determine how the lenses and mirrors are arranged.
How Reflector telescopes work:
The first step in the process of using a reflector telescope is to gather light from a distant object using the primary mirror.
The primary mirror is concave, which means that it bends the light that hits it. This bent light is then reflected off of the secondary mirror and into the eyepiece.
The eyepiece magnifies the image and makes it appear larger. The focuser is used to fine-tune the image that is being magnified by the eyepiece.
Reflector telescopes Parts
A reflector telescope is made of parts including; the tube, the primary mirror, the secondary mirror, the eyepiece and the focuser.
The Tube: The tube is the long, cylindrical part of the telescope that houses the mirrors and lenses. It is usually made of metal or fiberglass.
The Primary Mirror: The primary mirror is the large, concave mirror at the bottom of the tube. It is made of glass or metal and is used to gather light from distant objects. The primary mirror is usually the biggest mirror in the telescope.
The Secondary Mirror: The secondary mirror is a small, convex mirror that is mounted in front of the primary mirror. It reflects light from the primary mirror onto the eyepiece.
The Eyepiece: The eyepiece is a small lens that is mounted on the side of the tube. It magnifies the image that is reflected off of the primary mirror and secondary mirror.
The Focuser: The focuser is a mechanism that is used to move the eyepiece up and down in the tube. This is used to focus the image that is being magnified by the eyepiece.
There are advantages to how reflector telescopes work:
The first advantage is that they can be made much larger than refractor telescopes. The largest reflector telescope in the world is the Arecibo Observatory, which has a primary mirror that is 305 meters (1,000 feet) across!
Reflector telescopes also have another advantage over their refracting counterparts: they do not suffer from a phenomenon known as chromatic aberration.
Chromatic aberration is an optical error that occurs when different colors of light are not brought into focus at the same point. This is a problem for refractor telescopes because lenses are made of glass, which tends to disperse light into its component colors.
Drawbacks of reflector telescopes:
- One drawback of reflector telescopes is that they require regular maintenance and adjustment. The primary mirror needs to be perfectly aligned with the secondary mirror, otherwise the images will be blurry.
- Another drawback is that because the eyepiece is located off to the side of the telescope, it can be difficult to keep your eye on the object you are trying to view. This is why many reflector telescopes come with a diagonal mirror, which reflects the light at a 90-degree angle so that you can look directly through the eyepiece.
Who is suited to use reflector telescopes?
Reflector telescopes are a good choice for anyone who wants to view distant objects in the night sky. They are also a good choice for anyone who wants to take photographs or videos of those objects.
Cost:
The cost of reflector telescopes can vary depending on the size and quality of the telescope. A small, entry-level telescope can cost as little as $100, while a large, high-quality telescope can cost several thousand dollars.
What reflector telescopes can do/see:
Reflector telescopes can be used to view distant objects in the night sky, such as stars, planets, and galaxies. They can also be used to take photographs or videos of those objects.
Benefits:
The main benefit of reflector telescopes is that they can be made much larger than refractor telescopes. This allows them to gather more light, which means they can provide clearer images of distant objects.
Another benefit is that they do not suffer from chromatic aberration, which is an optical error that can occur in refractor telescopes.
Drawbacks:
The main drawback of reflector telescopes is that they require regular maintenance and adjustment. The primary mirror needs to be perfectly aligned with the secondary mirror, otherwise the images will be blurry.
Another drawback is that because the eyepiece is located off to the side of the telescope, it can be difficult to keep your eye on the object you are trying to view.
Below is an image of one of the leading reflector telescope brands going for under $200 on Amazon.
How Refractor telescopes:
Refractor telescopes (link to Wikipedia page) are made of several parts which include; an objective lens, a focuser, an eyepiece, and a diagonal mirror.
To magnify objects, a refractor telescope uses an objective lens. The lens is usually made of a piece of glass that has been ground and polished into a curved shape.
First, refractor telescopes gather light from a distant object using a large objective lens. The objective lens is usually convex, which means it has a curved surface that helps to focus the light.
The light is then passed through a second lens, called the eyepiece lens, which magnifies the image and makes it appear larger.
The eyepiece is located at the top of the telescope tube and it magnifies the image that is formed by the objective lens.
There are two types of refractor telescopes: achromatic and apochromatic.
- Achromatic refractor telescopes use two lenses made of different materials in order to correct for chromatic aberration.
- Apochromatic refractor telescopes use three or more lenses made of different materials in order to correct for chromatic aberration. These telescopes are typically more expensive than achromatic refractor telescopes.
Who are refractor telescopes for?
Now that you know a little bit about how telescopes work, you might be wondering which type is right for you.
Refractor telescopes are a good choice for beginners because they are relatively easy to use and require less maintenance than reflector telescopes.
Reflector telescopes are a good choice for people who want to view faint objects, such as galaxies and nebulae.
Both types of telescopes have their pros and cons, so it really depends on what you want to use them for.
If you are interested in viewing planets and stars, a refractor telescope would be a good choice. If you are interested in viewing faint objects such as galaxies and nebulae, a reflector telescope would be a better choice.
What is the size of the refractor telescope?
Refractor telescopes come in a wide range of sizes, from small tabletop models to large research-grade instruments. The largest refractor telescope in the world is the Yerkes Observatory telescope, which has an objective lens that is 102 centimeters (40 inches) across!
Advantages of refractor telescopes;
One advantage of refractor telescopes is that they are very easy to use. All you have to do is point the telescope in the direction you want to look and then look through the eyepiece.
Another advantage is that refractor telescopes do not require regular maintenance and adjustment like reflector telescopes do. This is because the lenses are sealed inside the telescope tube, so they cannot become misaligned.
Drawbacks of refractor telescopes;
One drawback of refractor telescopes is that they are susceptible to a phenomenon known as chromatic aberration.
Chromatic aberration is an optical error that occurs when different colors of light are not brought into focus at the same point. This is a problem for refractor telescopes because lenses are made of glass, which tends to disperse light into its component colors.
Another drawback of refractor telescopes is that they are often smaller than reflector telescopes. This is because it is difficult to create a large lens without distorting the image.
Refractor telescopes also tend to be more expensive than reflector telescopes. This is because the lenses are usually made of higher quality materials and they require more precise grinding and polishing.
Another drawback is that because the eyepiece is located in the front of the telescope, it can be difficult to keep your eye on the object you are trying to view. This is why many refractor telescopes come with a finderscope, which is a small telescope that helps you aim the larger telescope in the right direction.
Below is an image of Celestron – AstroMaster 90AZ Refractor Telescope retailing on Amazon for under $300.
How Catadioptric Telescopes Work;
Catadioptric telescopes are a type of telescope that uses both mirrors and lenses to gather and focus light.
Catadioptric telescopes work by first gathering light from a distant object using a large objective lens. The objective lens is usually convex, which means it has a curved surface that helps to focus the light.
The light then passes through a secondary mirror, which reflects the light at a 90-degree angle and sends it back through the objective lens.
Finally, the light passes through an eyepiece lens, which magnifies the image and makes it appear larger.
What is the size of Catadioptric telescopes?
Catadioptric telescopes come in a wide range of sizes, from small tabletop models to large research-grade instruments. The largest catadioptric telescope in the world is the Keck Observatory telescope, which has an objective lens that is 10 meters (33 feet) across!
Advantages of Catadioptric Telescopes;
One advantage of catadioptric telescopes is that they are very versatile. They can be used for a wide variety of applications, from astronomy to birdwatching.
Another advantage is that catadioptric telescopes are very portable. This is because they are usually smaller than other types of telescopes, so they can be easily transported from one location to another.
Drawbacks of Catadioptric Telescopes;
One drawback of catadioptric telescopes is that they are more expensive than other types of telescopes. This is because lenses and mirrors are made of glass, which is a costly material.
Another drawback is that catadioptric telescopes require regular maintenance and adjustment. This is because the lenses and mirrors can become misaligned over time.
Video Explanation of How Telescopes Work by BBC Earth Lab
FAQs
Q: How much does a telescope cost?
A: The price of a telescope can vary depending on the type, size, and features. A basic refractor telescope can cost as little as $100, while a high-end catadioptric telescope can cost upwards of $10,000. We have reviewed some of the best telescopes for under $500 here.
Q: How do I choose a telescope?
A: The type of telescope you choose should be based on your needs and budget. If you want a telescope for casual viewing of the night sky, then a refractor or Dobsonian telescope would be a good choice. If you are interested in doing serious astronomy research, then a catadioptric telescope would be a better option.
Q: What are the different types of telescopes?
A: There are three main types of telescopes: refractor, reflector, and catadioptric. Refractor telescopes use lenses to gather and focus light, while reflector telescopes use mirrors. Catadioptric telescopes use a combination of both lenses and mirrors.
Q: What are the different parts of a telescope?
A: The four main parts of a telescope are the objective lens, secondary mirror, eyepiece lens, and finderscope. The objective lens is the large lens at the front of the telescope that gathers light from distant objects. The secondary mirror reflects the light at a 90-degree angle and sends it back through the objective lens. The eyepiece lens magnifies the image and makes it appear larger. The finderscope helps you aim the telescope in the right direction.
Q: What are the different types of mounts?
A: There are two main types of mounts: altazimuth and equatorial. Altazimuth mounts are simpler and more common, while equatorial mounts are more sophisticated and are used for astronomical research.
Q: How do I set up my telescope?
A: The process of setting up a telescope depends on the type of mount it has. Altazimuth mounts are typically easier to set up, while equatorial mounts require a bit more effort.
Q: How do I align my telescope?
A: The process of aligning a telescope is called “collimation.” This involves adjusting the mirrors and lenses so that they are in the correct position.
Q: What are the different eyepieces?
A: There are three main types of eyepieces: Plössl, Erfle, and Orthoscopic. Plössl eyepieces are the most common type and offer a wide field of view. Erfle eyepieces have a wider field of view than Plössl eyepieces, but they produce a less sharp image. Orthoscopic eyepieces have a narrower field of view than the other two types, but they produce a very sharp image.
Q: What is the exit pupil?
A: The exit pupil is the diameter of the beam of light exiting the eyepiece. It is usually expressed in millimeters.
Q: What is focal length?
A: Focal length is the distance from the lens or mirror to the point where the image is in focus. It is usually expressed in millimeters.
Q: What is focal ratio?
A: The focal ratio is the ratio of the telescope’s focal length to its aperture. It is usually expressed as a number, such as f/5.
Q: What is the difference between Newtonian and Dobsonian telescopes?
A: Newtonian telescopes are reflector telescopes that use a mirror as the primary optics, while Dobsonian telescopes are a type of Newtonian telescope that uses a simple mount.
Q: What is the difference between a refractor and a catadioptric telescope?
A: Refractor telescopes use lenses to gather and focus light, while catadioptric telescopes use a combination of lenses and mirrors.
Q: What is the difference between an achromatic and apochromatic lens?
A: Achromatic lenses are less expensive than apochromatic lenses, but they do not correct for chromatic aberration as well. Apochromatic lenses are more expensive, but they corrected for chromatic aberration.