FOV is an incredibly important aspect of a telescope. It is a parameter that dictates how much of the sky you can view at any time with your telescope. How much of the sky you can see depends on the focal length of your telescope and the focal length of your eyepiece. You may ask what does FOV stand for; this article explains just that.
However, compared to focal length and magnification levels, FOV tends to become somewhat of an afterthought for many people. This is despite how drastically it can affect your viewing experience.
What follows is the full breakdown of FOV in relation to telescopes, including what it means. We also explain why it’s considered important and how you can calculate the true FOV of your telescope. At this point, you might also want to check out What Is Arcsec?.
What Does FOV Mean?
FOV is a very common term used in astronomy, remote sensing, photography, and even video games when using VR headsets. It is an acronym for field of view.
Field of view refers to how much of a scene you can see through a lens. So when using a telescope, it would mean how much of the sky you can see at any one time.
For example, you might have noticed that when using binoculars, you can view a wide area. However, when looking through the lens of a telescope, you can only observe a smaller area. This means that binoculars have a wider FOV. Incidentally, binoculars have a smaller field of view than the naked eye, which has a FOV of around 180 degrees.
To find this, you will simply need to divide the telescope’s overall focal length by the eyepiece’s focal length. This will give you the exact magnification.
So, for example, if you had an eyepiece that was 50mm in focal length and a telescope with an overall focal length of 1000mm, the magnification would be 20x.
You will then need to divide the eyepiece’s apparent field of view by the magnification level (you will need to find your eyepiece’s specifications to determine this). The number you arrive at will then be your true field of view in degrees. The result is the circle’s diameter that you can will see when looking through your telescope.
Our Telescope Calculator can determine the FOV and other important telescope parameters
Why Is It Important To Know The FOV Of Your Telescope?
Figuring out how much of the observable sky can see when using a telescope may seem fairly unimportant at first. This is especially true when you want to prioritize the quality of the image over the number of celestial bodies that you can observe.
That said, there are still a few reasons why knowing your FOV is worth knowing. It can make the viewing experience far easier and much more enjoyable.
Finding A Target
Many of us will use our telescopes to star-hop. Starhopping is when we use star charts and reference points to locate a particular object. This could be a planet or a specific star that we want to observe up close.
When using a telescope with a smaller and narrower FOV, it can make it easy to get lost while searching for your target. It is easy to get lost since it is easy to lose reference stars. It is easy to accidentally hop to a wrong star, getting back to your original position is much trickier.
Additionally, it’s crucial to know your field of view beforehand. This will allow you to know which stars you will be able to see through your eyepiece, making it much easier to arrive at your intended target.
Adjusting The Focus
A telescope that has a smaller field of view will also tend to possess a much higher magnification. These types of telescopes are primarily used for bright objects. They are great for observing the Moon and planets. However, they produced dim images and are not ideal for dim objects.
With a larger field of view, lower magnifications result. However, they provide a wider field which allows easy navigation of the night sky. Focusing will be easier and the image will be sharp. Also, larger objects will be visible in a single frame.
Visual Appeal
The beauty of wide-field astronomy and astrophotography is that we can view many elements of the universe. Such views fill us with wonder. However, with a limited field of view containing a single planet or a few stars it is easy to lose the sense of wonder. This is the reason why you should not just look at telescopes that provide high levels of magnification. Any telescope whose main marketing drive is on magnification should be avoided as they tend to be poor quality.
For example, Hyades or Alpha Persei star cluster are known for their bright stars and astonishing compositions. It can be easy to forget just how jaw-dropping these areas of the universe are when you’re zoomed in and only focusing on a single corner.
What You Can See With Your Field Of View
The exact FOV of your telescope will determine how many celestial bodies you can see at one time. So let’s take a look at a few examples.
If you have a field of view of 1.25°, which is considered very large. At this FOV, you will be able to see Venus, the entire disc of the Moon, and half of Orion’s Belt.
With a 0.50° field of view, you will only get sight of the Moon and Venus. However, they will look much larger and brighter thanks to the enhanced magnification.
If, however, you go really big and have a field of view of approximately 1.42°, you can see the Moon, Venus, and more than half of Orion’s Belt.
If you wish to simulate what you can see at different FOVs you can check out a telescope simulator.
Summary
There are so many benefits to determining your telescope’s true field of view. For that reason, it’s well worth knowing about. This is especially true since you can calculate it easily and adjust it to make your viewing experience music easier, depending on what you want to observe.
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.
