Exploring the Marvel of Magnification in Astrophotography

Shubham Kumar
2 min readOct 21, 2023

Welcome back to another exciting episode of “Understanding Astrophotography.” In this episode, we delve into the captivating world of magnification, a fundamental phenomenon at the heart of our understanding of the cosmos. Magnification, in simple terms, involves the art of enlarging an image of an object. You’re probably familiar with everyday tools that employ magnification, such as magnifying glasses, eyeglass lenses, binoculars, and telescopes.

The Role of Convex Lenses:

Let’s peel back the curtain and explore the inner workings of magnification. One of the most common instruments for magnification is the convex lens. This remarkable device utilizes the principles of refraction to create larger-than-life images. Allow us to elucidate how this optical magic unfolds.

Magnification by a Convex Lens. Image Source : https://www4.uwsp.edu/physastr/kmenning/Phys204/Lect24.html

Diverging Light Rays:

Picture this scenario: an object positioned between the convex lens and its focal point. As the incoming light rays pass through the lens, they undergo refraction. However, this time, they take a different path. The lens’s thicker center and thinner edges cause the rays to bend outward, away from the focal point.

Virtual Image Formation:

Intriguingly, in this setup, a virtual image materializes on the same side of the lens as the object. The image stands upright, not inverted, and seems as if it resides behind the object. But here’s the twist — this virtual image isn’t the result of actual light rays converging but rather an extrapolation of their paths backward into the lens.

Magnification Factor:

The magnitude of magnification in this context hinges on the relationship between the image distance and the object distance. This is akin to the situation when an inverted image is formed. Nevertheless, in this case, both the object and its corresponding image occupy the same side of the lens. The magnification factor can be positive because the image is erect and not inverted.

Apparent Enlargement:

While the image remains upright, it can still appear larger than the object due to the intriguing light-bending properties of the convex lens. The degree of this magnification depends on various factors, including the specific distances involved and the characteristics of the lens itself.

To sum it up, when an object is placed in front of the focal point of a convex lens and an upright, virtual image is formed, the light rays are bent outward. This creates a seemingly larger image on the same side of the lens as the object. This principle underpins a plethora of magnification tools, and its significance in astrophotography is profound. Join us in the next episodes to explore more fascinating concepts related to magnification and how they are instrumental in unveiling the wonders of the universe.