Keplerian Telescope and real image

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In summary, the Keplerian telescope, designed by Johannes Kepler, utilizes two convex lenses to magnify distant objects. The primary lens, or objective, gathers light and forms a real image, which is then viewed through a second lens, or eyepiece. This arrangement allows for a wider field of view and higher magnification compared to other telescope designs, making it a significant advancement in astronomical observation. The real image produced is inverted, which is a characteristic feature of this type of telescope.
  • #1
xchen2004
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Homework Statement
Imagine that you will build a Keplerian telescope and record the images that
it produces on a CCD chip. The CCD chip records the light intensity at each
pixel and thus can be used to produce an image, if the chip is at the location
of a real image. Draw how you will modify the basic Keplerian telescope to
accomplish this. Also, given that the magnification of a telescope is defined as
how much bigger it makes an object look to a given imaging system, does the
magnification change given your modification?
Relevant Equations
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I know that the Keplerian Telescope produces an inverted virtual image. What modification should I make to generate real images? Will switching the first lens with the second lens change the telescope into a microscope? Thank you!
 
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  • #2
Welcome to PF.

Can you post a link or two to information about Keperian telescopes and maybe use "Attach files" to upload a typical image of one? Then can you say more about why anything needs to get modified? Thanks.
 
  • #3
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Beams are not focused after the second lens. The telescope forms a virtual image. But I need form a real image after telescope to record image on chips.
 
  • #4
Okay, good, thanks. So what do you need to add in order to form a real image? Hint -- what does the eye add to form an image on its retina?
 
  • #5
You mean adding a third lens, so the light focuses on the focal point of the third lens, then forms a real image?
 
  • #6
That seems like a possibility to me. To form a high quality image, you would want the lens system that you add to be achromatic, but maybe in the context of a simple schoolwork problem, they just want you to insert a simple lens to form the real image.

What equations should you use to calculate the power of that new lens?
 
  • #7
I tried to achieve the task with only 2 lenses. I moved the second lens to the left of the right focal point of the first lens. I can indeed obtain a real image. However, after using ABCD matrix to calculate the angular magnification of the system, I found M<1, which means it is a microscope not a telescope..... Is there a way to achieve a telescope with only two lenses? It is part 1d. Thank you!
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  • #8
Isn't there already a real image in the drawing you posted of the Keplerian telescope? Can't you just put the CCD there?
 

FAQ: Keplerian Telescope and real image

What is a Keplerian telescope?

A Keplerian telescope, also known as a refracting telescope, is a type of optical telescope that uses two convex lenses to form an image. The first lens, called the objective lens, gathers light and brings it to a focus, while the second lens, called the eyepiece, magnifies the image produced by the objective lens. This design allows for a wider field of view and higher magnification compared to other types of telescopes.

How does a Keplerian telescope produce a real image?

A Keplerian telescope produces a real image when the light rays from a distant object converge after passing through the objective lens. The objective lens focuses these rays to form an image at its focal plane, which is a real image that can be projected onto a screen or captured by a camera. This image is inverted and can be further magnified by the eyepiece lens.

What are the advantages of using a Keplerian telescope?

Some advantages of using a Keplerian telescope include its ability to provide a wider field of view, higher magnification, and better image quality due to the use of two lenses. Additionally, the design minimizes chromatic aberration, which is the distortion of colors that can occur with single lens systems. The eyepiece allows for comfortable viewing and adjustments for different eye prescriptions.

What is the difference between a real image and a virtual image in telescopes?

A real image is formed when light rays converge at a point, allowing the image to be projected onto a surface, such as a screen. In contrast, a virtual image occurs when light rays appear to diverge from a point, making it impossible to project the image onto a surface; instead, it can only be viewed through the eyepiece. In a Keplerian telescope, the image formed by the objective lens is a real image, while the image seen through the eyepiece is a virtual image.

Can a Keplerian telescope be used for astrophotography?

Yes, a Keplerian telescope can be used for astrophotography. The real image produced by the telescope can be captured by a camera placed at the focal plane of the objective lens. However, additional equipment, such as a suitable camera adapter and tracking mounts, may be necessary to achieve optimal results, especially for long exposure times required in astrophotography.

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