What Is Magnification Power As It Pertains To Telescopes

What is Magnification Power as it Pertains to Telescopes?

An optical system has a very intricate relationship among each component. These components are independent yet work together in unison to produce accurate results.

Magnification in a telescope encompasses this complicated relationship between different optical instruments. For this reason, it is essential to understand the exchange and its calculations.

What is a magnification power concerning a telescope?

For better utility, you must combine two lenses in an optical instrument. The entirety of your scope, along with the eyepiece is the element controlling the magnifying power.

Your telescope provides an enlarged view of distant celestial objects. Astronomers must study the magnifying power of their scope for better results.

The objective lens is equipped for performing the real image of the object you are viewing. This actual image then gets processed by a second lens- the eyepiece.

When you fine-tune your scope and make adequate adjustments, the eyepiece forms the final image. The final image formed is truly imaginary.

The resultant image that is formed complies with the concepts for exit pupil and eye relief. The focal point becomes a landmark for the first image. This is true when it is located at a larger distance.

Now you focus the eyepiece so that the primary focal point and first image location coincide. This means your final image, which is imaginary, is located infinitely farther away.

You can switch your immediate objective with a different one having varied focal lengths. This will change the resultant power of your telescope. The power either increases or decreases.

What is the angular magnification?

The angle produced by the final image is divided by the angle formed by the object. This gives you a unit, called angular magnification. This is true when you are viewing the purpose with a naked eye.

In an ideal scenario, this is the position where the two focal points coincide with each other.

How to calculate the magnifying power of your telescope?

The method we specify in this article is straightforward. You do not need specific instruments or in-depth knowledge of the refraction index for a better deduction.

You divide the eyepiece diameter with the focal length. Here is an equation to help you fare better.

For better clarity, it is essential to know that the eyepiece diameter is also called the eyepiece focal length.  This concept is entirely different from that of the exit pupil.

What are the limitations of magnifying power in a telescope?

Specific optical rules govern the limitations of the magnifying power of your scope. They are also subject to the biological capabilities of the human eye or the observer’s eye.

As a general practice, you can use a maximum power of 50 to 60 times greater than the scope’s aperture. This is only true when the conditions are virtually ideal.

If you use a power higher than this unit, the resultant image is dimly lit, low contrast image. With increasing power, the sharpness and visible details will be decreased.

Astronomers prefer high powered telescope for a binary star, planetary and lunar observations. Most of your astronomical endeavours will be carried out with a low-powered telescope.

With low power, the final image is bright, sharp. This makes your astronomical observations fruitful as the field of view is broader.

As a beginner, you must begin with the lowest available magnification of your scope. The lowest power will have the longest focal length.

Once you have perfected with low power, then you can move up the ladder with higher magnifications.

When you are using a high-powered telescope, a Barlow’s lens becomes a useful aid. We elaborate on this versatile device in the section down below.

The Barlow lens for high-powered astronomy

As an amateur astronomer, a Barlow’s lens can make your astronomical goals easier to reach. The lens is placed between the objective lens or the mirror and the eyepiece of your scope.

Once the lens is placed in its position, it will amplify the magnification of your telescope. There is a specific mechanism that enables the lens to produce high-quality results.

Barlow’s lens decreases the convergence of the cone of light. By doing this, it is fundamentally reducing the focal length of your scope.

Since the magnification is determined by dividing the focal length of the eyepiece and telescope. The Barlow doubles the focal length of the scope. This helps the device to enhance its magnification.

There are several advantages to using a Barlow lens. You can reach a better maximum power with this aid. The lens is especially useful when it comes to telescopes with short focal lengths.


  1. telescope.com
  2. Celestron
  3. Astronomy Online

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