Telescopes are the best tools at your disposal when you want to look at celestial objects in detail. Of course, that isn’t the only thing they’re helpful for, as they can help photograph the stars above and observe the goings-on in outer space. To understand telescopes an important question to answer is what are the two most important properties of a telescope.
If there’s an object far away, you can see it with your telescope.
Of course, that doesn’t mean that telescopes are only used for astronomy. Telescopes are essential for navigating sailors, and they can help you see distant sights you wouldn’t otherwise see.
Bird watchers and hunters can also use telescopes to look closely at the animals they observe. Due to all these uses, you must know your telescope’s two most important properties.
The Two Most Important Properties Of A Telescope
You’ll find two essential properties to consider depending on how you use your telescope. First, you must know how good your telescope’s light-gathering ability.
Secondly, you need to know how well it can magnify objects. Now, let’s go into more detail about these properties’ importance.
Light Gathering Ability
When a telescope gathers light, it can see objects further away. A better ability to gather light will enable you to see stars and other faint objects you couldn’t see with the naked eye.
Not all telescopes have the same light-gathering ability, which is determined by the size of the aperture.
The aperture is the diameter of the region collecting light, assuming the region has a circular geometry.
For example, the aperture is either the diameter of the objective lens in a refracting telescope or the primary mirror in a reflecting telescope. We’ll go into more detail about the two types of telescopes later.
While we also list magnification as an important property, the amount of magnification possible is a function of the aperture. A wider aperture allows higher magnification as more light allows for more magnification. The telescope’s aperture limits the maximum magnification.
Magnification Ability
The magnification ability of a telescope is exactly as it’s described. Using the magnification of your telescope, you’ll see how much larger it will make the objects you see through it.
These two properties need to be considered, with most telescopes having a better use for either light gathering or magnification.
Two Of The Main Types Of Telescopes
Now that we’ve told you about the two most important properties, we can go into more detail about the two main types of telescopes. Each prioritizes one of the properties mentioned above. These types are refracting telescopes and reflecting telescopes.
What Is A Refracting Telescope?
A refracting telescope uses lenses to magnify the image you see. Refracting telescopes can do this by bending the light to a specific focal point within the telescope. Doing this, the object will then appear to be magnified to you upon looking through the telescope.
Most basic refracting telescopes have two lenses. The first lens is the objective lens, a convex lens that can bend incoming light rays to a focal point in your telescope. The second lens is the eyepiece.
Using the eyepiece, the light is taken from the focal point, and it then spreads across your eye’s retina, so the object you’re viewing is closer than it is.
Refracting telescopes suffer from aberrations that can be corrected. See our post on refracting telescopes for more information.
What Is A Reflecting Telescope?
Instead of using lenses, a reflecting telescope uses mirrors to focus the object’s light. To do this, the telescope has a concave mirror that gathers light and reflects it toward the focal point.
The light escapes the telescope using another mirror to direct it towards the eyepiece. You’ll find numerous designs for reflecting telescopes, but the original design from Isaac Newton is still widely used to this day.
Since the late 1600s, people have used Newton’s design for the reflecting telescope. He first designed this to improve upon the issues found with refracting telescopes.
The Benefits Of Refracting And Reflecting Telescopes
Both of these telescopes have significant benefits you must consider before purchasing a telescope. If you’re new to astronomy, here are some reasons you should consider these telescopes.
Benefits Of Refracting Telescopes
The main benefit of a refracting telescope is that the lenses seal both sides of the tube. Therefore, it’s difficult to get dirt inside of them, making them easier to clean.
Because they’re sealed, air can move freely inside the tube, so the images you see are often sharper and steadier than other telescopes.
Benefits Of Reflecting Telescopes
Many people prefer to use reflecting telescopes as they’re more affordable than refracting telescopes and don’t suffer from the same issues. This is particularly true at larger apertures.
For example, a reflecting telescope has no issues with chromatic aberration, while refracting telescopes do. Also, due to the way they’re made, reflecting telescopes can be larger than refracting telescopes, as the mirror can be fixed onto a metal plate.
Disadvantages Of Refracting And Reflecting Telescopes
Naturally, both of these telescopes have disadvantages that come with them too. Here are a few issues that we have found.
Disadvantages Of Refracting Telescopes
One of the biggest issues with refracting telescopes is that it’s quite uncomfortable to use. If you’re pointing it into the night sky, you must crouch down and crane your neck to see through the eyepiece properly.
While some telescopes do some with prism adaptors to make this more comfortable, they don’t always include them. If your telescope does not come with one we strongly recommend purchasing on of these diagonals.
Likewise, we’ve mentioned before that refracting telescopes can suffer from chromatic aberration. Chromatic aberration is when the image’s color distorts. Chromatic aberration causes color fringes on stars.
As the aperture of a refracting telescope increases, the cost of producing the lens increases quickly. As a result, large aperture refracting telescopes are prohibitively expensive.
Disadvantages Of Reflecting Telescopes
One challenge with using a reflecting telescope is that it can be difficult to see through the eyepiece. These telescopes are often much larger than refracting telescopes, with some requiring a stepladder to see through them.
However, to avoid this, you can get more compact reflecting telescopes, known as Cassegrain telescopes, that are half the length of your usual Newtonian reflecting telescope.
Final Thoughts
As you can see, the two main properties of a telescope can help you decide which type of telescope you should invest in. When looking at your telescope, consider what you want to use it for, and you can identify it by these two essential properties.
If you wish to delve into the other telescope properties and calculate them for your telescope see Telescope Calculator.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
