What is the field of view of a telescope and why do telescopes use a large field of view

The angular diameter of the area of the sky that can be well imaged by the telescope is called the field of view of the telescope or the angle of view of the field of view ( ) The field of view of a telescope is often determined at the time of design. The field of view of a telescope is inversely proportional to magnification, and the greater the magnification, the smaller the field of view. Different optical systems, different imaging qualities (due to aberrations), different apertures, and different focal lengths determine the size of the telescope's different fields of view (in the case of astrophotography, the size of the negatives or CCDs also constrains the size of the field of view).

Reflecting telescopes have the smallest field of view, generally less than 1 degree; Refracting telescopes are larger, reaching several degrees; The catadioptric telescope has the largest field of view, which can reach more than ten or even dozens of degrees.

Want an example? That's good:

Niu anti 150750, equipped with a PL20mm eyepiece, asked what is the field of view?

Answer: The magnification is f-object fmesh = 750mm 20mm = true field of view = apparent field of view magnification.

The apparent field of view of the Proser eyepiece is 50° 55°, so the actual field of view is left and right.

True field of view. The eyepiece also determines the actual extent of the area of the sky you see. To calculate the actual field of view area (degrees), divide the diameter of the field diaphragm of the eyepiece by the focal length of the telescope and multiply:

True field of view (power) The diameter of the field diaphragm of the eyepiece The focal length of the telescope x

For example: The focal length of the objective lens is 900mm, 66 degrees.

Wide-angle eyepiece: eyepiece focal length 20mm, field diaphragm.

True field of view (degrees) x degrees.

The diameter of the moon occupies a direct one-third of the field of view).

Magnification 900

20 45 times.

This eyepiece has a field of view of 66 degrees.

Summary. Hello, glad to answer for you!

The principle of the telescope is that the convex lens is magnified into an inverted real image and an enlarged upright virtual image, the most important thing is to increase the clear aperture, the larger the clear aperture, the more light collected, the higher the resolution of the seen image.

Why do telescopes use large fields of view?

Hello, glad to answer for you! The principle of gliding sailing with telephoto mirror is that the convex lens is magnified into an inverted real image and into a magnified upright signal hail virtual image, the most important thing is to increase the clear aperture, the more light collected the larger the clear aperture, the higher the resolution of the seen image.

Of course, the larger the aperture, the viewing angle will also increase, but usually the increase in the viewing angle is to work on the eyepiece so that the light can be shot into the telescope from a wider angle, but the increased angle will not be greater than a few seconds, and at the same time it causes more interference light to enter, so that it is very unfavorable to observe the weaker light of the star in the hunger zone The same as our common sense, the same object, if it is close to us, we feel that it has become larger, in fact, its size has not changed, what has changed is the distance, which leads to the increase of the viewing angle without a sign;And if the distance does not change but the object increases on its own, we will also see that it becomes larger (the angle of view increases), in other words, the angle of view is also related to the size. If two objects are very different in size and at different distances, it is possible to see them "seeming" to be of equal size, as is the case with the Sun and the Moon. If the angle of view is too small when we look at the object directly, it will be difficult for us to observe its details and only see a rough idea, so we need to use tools to increase the angle of view and increase our resolution.

Just as we see a planet as a small dot with the naked eye, when we zoom in with a telescope, we will find that the planet has many details that are not discernible to the naked eye, which are too small to the naked eye because of the distance.

True field of view.

The eyepiece also determines the actual extent of the area of the sky you see. To calculate the actual field of view area (degrees), divide the diameter of the field diaphragm of the eyepiece by the focal length of the telescope and multiply:

True field of view (power) Field diaphragm diameter of eyepiece Focal length of telescope x Example: Objective focal length 66 degrees Wide-angle eyepiece: Eyepiece focal length Field diaphragm.

True field of view (degrees) = 900 x = degrees (the diameter of the moon is directly one-third of the field of view).

Magnification 900 20 45 times.

This eyepiece has a field of view of 66 degrees.